query: what is the electron domain geometry about phosphorus in the hexafluorophosphate anion ( pf 6  − )

pos: Hexafluorophosphate Hexafluorophosphate Hexafluorophosphate is an anion with chemical formula of . It is an octahedral species. It imparts no color to its salts. is isoelectronic with sulfur hexafluoride, SF, and the hexafluorosilicate dianion, , and fluoroantimonate . Being poorly nucleophilic, hexafluorophosphate is classified as a non-coordinating anion. Hexafluorophosphate salts can be prepared by the reaction of phosphorus pentachloride and alkali or ammonium halide in a solution of hydrofluoric acid: Hexafluorophosphoric acid can be prepared by direct reaction of hydrogen fluoride with phosphorus pentafluoride. It is a strong Brønsted acid that is typically generated "in situ" immediately prior to its use. These

pos: Hexafluorophosphate for these applications. Room temperature ionic liquids such as 1-butyl-3-methylimidazolium hexafluorophosphate (typically abbreviated as bmimPF) have been prepared. The advantage of the anion exchange in favour of a non-coordinating anion is that the resulting ionic liquid has much greater thermal stability. 1-Butyl-3-methylimidazolium chloride decomposes to "N"-methylimidazole and 1-chlorobutane or to "N"-butylimidazole and chloromethane. Such decompositions are not possible for bmimPF However, thermal decompositions of hexafluorophosphate ionic liquids to generate hydrogen fluoride gas are known. Hexafluorophosphate Hexafluorophosphate is an anion with chemical formula of . It is an octahedral species. It imparts no color to its salts. is isoelectronic with sulfur

pos: Hexafluorophosphoric acid attacks glass. Upon heating, it decomposes to generate HF. Crystalline has been obtained as the hexahydrate, wherein is enclosed in truncated octahedral cages defined by the water and protons. NMR spectroscopy indicates that solutions derived from this hexahydrate contain significant amounts of HF. Hexafluorophosphoric acid Hexafluorophosphoric acid is the inorganic compound with the chemical formula HOPF. Although the formula is often written as HPF, this compound is only available as the hydrate. This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride. Like many strong acids, hexafluorophosphoric acid

pos: Tetrafluoroborate diminish the basicity of the anion. Related to is hexafluorophosphate, , which is even more stable toward hydrolysis and whose salts tend to be more lipophilic. Illustrative of a fluoroborate salt is [Ni(CHCHOH)](BF), a kinetically labile octahedral complex, which is used as a source of Ni. Extremely reactive cations such as those derived from Ti, Zr, Hf, and Si do in fact abstract fluoride from , so in such cases is not an "innocent" anion and less coordinating anions must be employed. Moreover, in other cases of ostensibly "cationic" complexes, the fluorine atom acts as a bridging ligand between boron

pos: T-shaped molecular geometry equatorial positions, and the three ligand atoms occupy the two axial positions as well as one equatorial position. The three atoms bond at 90° angles on one side of the central atom, producing the T shape. The trifluoroxenate(II) anion, , has been investigated as a possible first example of an AXE molecule, which might be expected by VSEPR reasoning to have six electron pairs in an octahedral arrangement with both the three lone pairs and the three ligands in a "mer" or T-shaped orientations. Although this anion has been detected in the gas phase, attempts at synthesis in solution and

pos: Pentavalent uranyl complexes phenoxide (salophen) and β-diketonate ligands are bound along the equatorial plane, which stabilizes the U species obtained by the single electron reduction of U species. Anhydrous uranyl triflate compounds (Figure 2, compound 4) contains discrete cation-anion pairs and it is synthesized by the crystallization of [UO(OPPh)][OTf]. U containing cation in this uranyl triflate compound shows an octahedral geometry. All uranium compounds are radioactive and toxic. Uranium compounds cause blood disorders, renal insufficiency, acute tubular necrosis, chronic fatigue and congenital disorders. The target organs are kidneys, liver, lungs and brain. Uranyl salts are neurotoxins and accumulates in bones, liver, kidneys, reproductive

neg: Ferrocenium hexafluorophosphate Ferrocenium hexafluorophosphate Ferrocenium hexafluorophosphate is an organometallic compound with the formula [Fe(CH)]PF. This salt is composed of the cation [Fe(CH)] and the hexafluorophosphate anion (). The related tetrafluoroborate is also a popular reagent with similar properties. The cation is often abbreviated Fc or CpFe. The salt is deep blue in color and paramagnetic. Ferrocenium salts are one-electron oxidizing agents, and the reduced product, ferrocene, is relatively inert and readily separated from ionic products. The ferrocene–ferrocenium couple is often used as a reference in electrochemistry. In acetonitrile solution that is 0.1 M in NBuPF, the Fc/Fc couple is +0.641 V with

neg: Phosphorus derived from hydrogen phosphate (HPO). PCl and PF are common compounds. PF is a colourless gas and the molecules have trigonal bipyramidal geometry. PCl is a colourless solid which has an ionic formulation of PCl PCl, but adopts the trigonal bipyramidal geometry when molten or in the vapour phase. PBr is an unstable solid formulated as PBrBrand PI is not known. The pentachloride and pentafluoride are Lewis acids. With fluoride, PF forms PF, an anion that is isoelectronic with SF. The most important oxyhalide is phosphorus oxychloride, (POCl), which is approximately tetrahedral. Before extensive computer calculations were feasible, it was

neg: Tetrakis(acetonitrile)copper(I) hexafluorophosphate Tetrakis(acetonitrile)copper(I) hexafluorophosphate Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a coordination compound with the formula [Cu(CHCN)]PF. It is a colourless solid that is used in the synthesis of other copper complexes. It is a well-known example of a transition metal nitrile complex. As confirmed by X-ray crystallographic studies, copper(I) ion is coordinated to four almost linear acetonitrile ligands in a nearly ideal tetrahedral geometry. Related complexes are known with other anions including the perchlorate, tetrafluoroborate, and nitrate. With the weakly coordinating anion B(CF), salts of [Cu(CHCN)] are obtained. The acetonitrile ligands protect the Cu ion from oxidation to Cu. However, acetonitrile is not bound

neg: Silver hexafluorophosphate ferrocene is oxidised to ferrocenium hexafluorophosphate: In terms of their properties and applications, silver tetrafluoroborate (AgBF) and the hexafluoroantimonate (AgSbF) are similar to AgPF. Silver nitrate is a traditional and less expensive halide abstraction reagent, as indicated by its widespread use in qualitative tests for halides. Relative to AgPF, however, silver nitrate is poorly soluble in weakly basic solvents: the nitrate anion is Lewis basic and presents an interfering ligand that precludes its use in stringent applications. Silver hexafluorophosphate Silver hexafluorophosphate, sometimes referred to "silver PF-6," is an inorganic compound with the chemical formula AgPF. Silver hexafluorophosphate is a commonly

neg: Silver hexafluorophosphate Silver hexafluorophosphate Silver hexafluorophosphate, sometimes referred to "silver PF-6," is an inorganic compound with the chemical formula AgPF. Silver hexafluorophosphate is a commonly encountered reagent in inorganic and organometallic chemistry. It is commonly used to replace halide ligands with the weakly coordinating hexafluorophosphate anion; the abstraction of the halide is driven by the precipitation of the appropriate silver halide. Illustrative is the preparation of acetonitrile complexes from a metal bromide, a reaction that would typically be conducted in a solution of acetonitrile: AgPF can act as an oxidant, forming silver metal as a by-product. For example, in solution in dichloromethane,

neg: Ferrocenium hexafluorophosphate respect to the normal hydrogen electrode. Commercially available, this compound may be prepared by oxidizing ferrocene with ferric salts followed by addition of hexafluorophosphoric acid. The compound has been characterized by X-ray crystallography. The cation and anion are well separated. The average Fc-C bond lengths is 2.047 Å, which is virtually indistinguishable from the Fe-C distance in ferrocene. Ferrocenium hexafluorophosphate Ferrocenium hexafluorophosphate is an organometallic compound with the formula [Fe(CH)]PF. This salt is composed of the cation [Fe(CH)] and the hexafluorophosphate anion (). The related tetrafluoroborate is also a popular reagent with similar properties. The cation is often abbreviated Fc

neg: Hexafluorophosphate Tetrakis(acetonitrile)copper(I) hexafluorophosphate is produced by the addition of hexafluorophosphoric acid to a suspension of copper(I) oxide in acetonitrile: While the hexafluorophosphate ion is generally inert and hence a suitable counterion, its solvolysis can be induced by highly electrophilic metal centers. For example, the tris(solvento) rhodium complex [("η"-CMe)Rh(MeCO)](PF) undergoes solvolysis when heated in acetone, forming a difluorophosphate-bridged complex [("η"-CMe)Rh(μ-OPFO)Rh(η-CMe)]PF. Practical uses of the hexafluorophosphate ion typically exploit one or more of the following properties: that it is a non-coordinating anion; that hexafluorophosphate compounds are typically soluble in organic solvents, particularly polar ones, but have low solubility in aqueous solution; or, that

neg: Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate is an organoruthenium compound with the formula [(CH)Ru(NCCH)]PF, abbreviated [CpRu(NCMe)]PF. It is a yellow-brown solid that is soluble in polar organic solvents. The compound is a salt consisting of the hexafluorophosphate anion and the cation [CpRu(NCMe)]. In coordination chemistry, it is used as a source of RuCp for further derivitization. In organic synthesis, it is a homogeneous catalyst. It enables C-C bond formation and promotes cycloadditions. The cyclopentadienyl ligand (Cp) is bonded in an η manner to the Ru(II) center. The title complex is synthesized in two steps from the (benzene)ruthenium dichloride dimer. In the first

neg: Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate step, the Cp group is installed using cyclopentadienylthallium: The second step entails photochemical displacement of the benzene ligand, which is replaced by three equivalents of acetonitrile (MeCN): Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate Tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate is an organoruthenium compound with the formula [(CH)Ru(NCCH)]PF, abbreviated [CpRu(NCMe)]PF. It is a yellow-brown solid that is soluble in polar organic solvents. The compound is a salt consisting of the hexafluorophosphate anion and the cation [CpRu(NCMe)]. In coordination chemistry, it is used as a source of RuCp for further derivitization. In organic synthesis, it is a homogeneous catalyst. It enables C-C bond formation and promotes cycloadditions. The cyclopentadienyl ligand

neg: Photoredox catalysis susceptible to oxidation than benzyl ethers because they are more electron-rich. The selective deprotection of PMB ethers can be achieved through the use of bis-(2-(2',4'-difluorophenyl)-5-trifluoromethylpyridine)-(4,4'-ditertbutylbipyridine)iridium(III) hexafluorophosphate (Ir[dF(CF)ppy](dtbbpy)PF) and a mild stoichiometric oxidant such as bromotrichloromethane, CBrCl. The photoexcited iridium catalyst is reducing enough to fragment the polyhalomethane compound to form trichloromethyl radical, bromide anion and the Ir(IV) oxidation state of the catalyst. The electron-poor nature of the fluorinated ligands means that this iridium complex can be readily reduced: in particular, by an electron-rich arene such as a para-methoxy benzyl ether. After the arene is oxidized, it will readily participate in

neg: Rhodocene extensive, with organometallic complexes of the pentamethylcyclopentadienyl and pentaphenylcyclopentadienyl ligands being well-known. Substitutions on the cyclopentadienyl rings of rhodocenes and rhodocenium salts produce compounds of higher stability as they allow for the increased delocalisation of positive charge or electron density and also provide steric hindrance against other species approaching the metal centre. Various mono- and di-substituted rhodocenium species are known, but substantial stabilisation is not achieved without greater substitutions. Known highly substituted rhodocenium salts include decamethylrhodocenium hexafluorophosphate [(η-CMe)Rh]PF, decaisopropylrhodocenium hexafluorophosphate [(η-CPr)Rh]PF, and octaphenylrhodocenium hexafluorophosphate [(η-CPhH)Rh]PF. Decamethylrhodocenium tetrafluoroborate can be synthesised from the tris(acetone) complex [(η-CMe)Rh(MeCO)](BF) by reaction with pentamethylcyclopentadiene, and

neg: Phosphaethynolate shows ambidentate nucleophilic tendencies towards the W(0) complex mentioned above. This is the result of a reduced difference in electronegativity between E and X thus neither atom offers a substantial advantage over the other in terms of providing ionic contributions to bonding. As a result, the average electron density in PCS is spread over the entire anion (see Figure 8) whereas in PCO, most electron density is localised on the phosphorus atom (see Figure 7) as this is the atom which bonds to form the thermodynamically favourable product. Phosphaethynolate The phosphaethynolate anion is the phosphorus-containing analogue of the cyanate anion

neg: Phosphenium of the linear versus bent geometries of nitrosyl. Highly electron-rich metal complexes were observed to have pyramidal phosphorus, while less electron-rich metals showed greater phosphenium character at the phosphorus. Pyramidal phosphorus indicates significant lone pair character at phosphorus, suggesting that the L→M σ donation and the M→L π backbonding interactions have been replaced with M→L σ donation, formally oxidizing the metal center by two electrons. Calculated geometries of the model phosphenium ions [PH], [PF], and [P(NH)] agree with the observed geometries. Density functional theory (DFT) calculations of the model compounds using the B3LYP 6-31G** basis set yielded orbital diagrams that

neg: Phosphaethynolate Phosphaethynolate The phosphaethynolate anion is the phosphorus-containing analogue of the cyanate anion with the chemical formula [PCO] or [OCP]. The anion has a linear geometry and is commonly isolated as a salt. When used as a ligand, the phosphaethynolate anion is ambidentate in nature meaning it forms complexes by coordinating via either the phosphorus or oxygen atoms. This versatile character of the anion has allowed it to be incorporated into many transition metal and actinide complexes but now the focus of the research around phosphaethynolate has turned to utilising the anion as a synthetic building block to organophosphanes. The first

neg: Tetrakis(3,5-bis(trifluoromethyl)phenyl)borate which are unlikely to bind directly to the metal centre of a complex. Hexafluorophosphate is a non-coordinating anion in both senses of the term. Three widely used non-coordinating anions are hexafluorophosphate, tetrafluoroborate , and perchlorate ; of these, the hexafluorophosphate ion has the least coordinating ability and it is deliberately used for this property. BARF was developed as a new non-coordinating anion in the 1990s, and is far less coordinating than even the hexafluorophosphate anion. NaBAr can be used in deprotection of acetal or ketal-protected carbonyl compounds. For example, deprotection of 2-phenyl-1,3-dioxolane to benzaldehyde can be achieved in water in

neg: Potassium hexafluorophosphate tetrafluoroborates. Potassium hexafluorophosphate Potassium hexafluorophosphate is the chemical compound with the formula KPF. This colourless salt consists of potassium cations and hexafluorophosphate anions. It is prepared by the reaction: This exothermic reaction is conducted in liquid hydrogen fluoride. The salt is stable in hot alkaline aqueous solution, from which it can be recrystallized. The sodium and ammonium salts are more soluble in water whereas the rubidium and caesium salts are less so. KPF is a common laboratory source of the hexafluorophosphate anion, a non-coordinating anion that confers lipophilicity to its salts. These salts are often less soluble than the closely

neg: Potassium hexafluorophosphate Potassium hexafluorophosphate Potassium hexafluorophosphate is the chemical compound with the formula KPF. This colourless salt consists of potassium cations and hexafluorophosphate anions. It is prepared by the reaction: This exothermic reaction is conducted in liquid hydrogen fluoride. The salt is stable in hot alkaline aqueous solution, from which it can be recrystallized. The sodium and ammonium salts are more soluble in water whereas the rubidium and caesium salts are less so. KPF is a common laboratory source of the hexafluorophosphate anion, a non-coordinating anion that confers lipophilicity to its salts. These salts are often less soluble than the closely related

neg: Ionic liquids in carbon capture (SILPs) are one proposed solution to this problem. As required for all separation techniques, ionic liquids exhibit selectivity towards one or more of the phases of a mixture. 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF) is a room-temperature ionic liquid that was identified early on as a viable substitute for volatile organic solvents in liquid-liquid separations. Other [PF]- and [BF]- containing ionic liquids have been studied for their CO absorption properties, as well as 1-ethyl-3-methylimidazolium (EMIM) and unconventional cations like trihexyl(tetradecyl) phosphonium ([P]). Selection of different anion and cation combinations in ionic liquids affects their selectivity and physical properties. Additionally, the organic cations in

neg: Phosphorus pentafluoride structures are, relative to a molecule in solution, static and can not undergo the necessary changes in atomic position. Phosphorus pentafluoride Phosphorus pentafluoride, PF, is a phosphorus halide. It is a colourless, toxic gas that fumes in air. Phosphorus pentafluoride was first prepared in 1876 by the fluorination of phosphorus pentachloride using arsenic trifluoride, which remains a favored method: Single-crystal X-ray studies indicate that the PF has trigonal bipyramidal geometry. Thus it has two distinct types of P−F bonds (axial and equatorial): the length of an axial P−F bond is distinct from the equatorial P-F bond in the solid phase,

neg: Phosphorus pentafluoride Phosphorus pentafluoride Phosphorus pentafluoride, PF, is a phosphorus halide. It is a colourless, toxic gas that fumes in air. Phosphorus pentafluoride was first prepared in 1876 by the fluorination of phosphorus pentachloride using arsenic trifluoride, which remains a favored method: Single-crystal X-ray studies indicate that the PF has trigonal bipyramidal geometry. Thus it has two distinct types of P−F bonds (axial and equatorial): the length of an axial P−F bond is distinct from the equatorial P-F bond in the solid phase, but not the liquid or gas phases due to Pseudo Berry Rotation. Fluorine-19 NMR spectroscopy, even at temperatures as

neg: Tetrakis(3,5-bis(trifluoromethyl)phenyl)borate Tetrakis(3,5-bis(trifluoromethyl)phenyl)borate Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate is an anion with chemical formula [{3,5-(CF)CH}B], which is commonly abbreviated as [BAr] as the boron atom (B) is surrounded by four fluorinated aryl (Ar) groups. It is sometimes referred to as "Kobayashi's anion" in honour of Hiroshi Kobayashi who led the team that first synthesised it, but more commonly it is affectionately nicknamed "BARF." BARF has a tetrahedral geometry around the central boron atom but each of the four surrounding aryl groups is aromatic and planar. The motivation for its preparation was the search for an anion which coordinates more weakly than the then-available ions hexafluorophosphate, tetrafluoroborate,

neg: Non-coordinating anion salts are more soluble in non-polar organic solvents such as dichloromethane, toluene, and, in some cases, even alkanes. Polar solvents, such as acetonitrile, THF, and water tend to bind to electrophilic centers, in which cases, the use of a non-coordinating anion is pointless. Salts of the anion were first reported by Kobayashi and co-workers. For that reason, it is sometimes referred to as "Kobayashi's anion". Kobayashi's method of preparation has been superseded by a safer route. The neutral molecules that represent the parents to the non-coordinating anions are strong Lewis acids, e.g. boron trifluoride, BF and phosphorus pentafluoride, PF. A

neg: Hypervalent molecule the ligands are more electronegative than the central, hypervalent atom, resonance structures can be drawn with no more than four covalent electron pair bonds and completed with ionic bonds to obey the octet rule. For example, in phosphorus pentafluoride (PF), 5 resonance structures can be generated each with four covalent bonds and one ionic bond with greater weight in the structures placing ionic character in the axial bonds, thus satisfying the octet rule and explaining both the observed trigonal bipyramidal molecular geometry and the fact that the axial bond length (158 pm) is longer than the equatorial (154 pm). For

neg: Trigonal bipyramidal molecular geometry Trigonal bipyramidal molecular geometry In chemistry a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not identical (see also pentagonal bipyramid), because there is no geometrical arrangement with five terminal atoms in equivalent positions. Examples of this molecular geometry are phosphorus pentafluoride (PF), and phosphorus pentachloride (PCl) in the gas phase. The five atoms bonded to the central atom are not all equivalent, and two different types of position are

neg: Hexafluorophosphoric acid Hexafluorophosphoric acid Hexafluorophosphoric acid is the inorganic compound with the chemical formula HOPF. Although the formula is often written as HPF, this compound is only available as the hydrate. This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride. Like many strong acids, hexafluorophosphoric acid is not isolable but is handled only in solution. Its aqueous solutions consist of hydronium ion, , and . Additionally, such solutions often contain products derived from hydrolysis of the P-F bonds, including , , and , and their conjugate bases. Hexafluorophosphoric acid

neg: Tetrakis(acetonitrile)copper(I) hexafluorophosphate very strongly to the copper ion, thus the complex is a useful source of Cu(I). The cation was first reported in 1923 with a nitrate anion as a byproduct of the reduction of silver nitrate with a suspension of copper powder in acetonitrile. [Cu(CHCN)]PF is generally produced by the addition of HPF to a suspension of copper(I) oxide in acetonitrile: The reaction is highly exothermic, and may bring the solution to a boil. Upon crystallization, the resulting microcrystals should be white, though a blue tinge is common, indicating the presence of a Cu species. As the coordinated acetonitrile ligands may

neg: Lithium hexafluorophosphate to the Lewis acidity of the Li ions, LiPF also catalyses the tetrahydropyranylation of tertiary alcohols. Lithium hexafluorophosphate Lithium hexafluorophosphate is an inorganic compound with the formula LiPF. It is a white crystalline powder. It is used in commercial secondary batteries, an application that exploits its high solubility in non aqueous, polar solvents. Specifically, solutions of lithium hexafluorophosphate in propylene carbonate and dimethoxyethane serve as an electrolyte in lithium batteries. This application also exploits the inertness of the hexafluorophosphate anion toward strong reducing agents, such as lithium metal. The salt is relatively stable thermally, but loses 50% weight at 200

neg: Lithium hexafluorophosphate Lithium hexafluorophosphate Lithium hexafluorophosphate is an inorganic compound with the formula LiPF. It is a white crystalline powder. It is used in commercial secondary batteries, an application that exploits its high solubility in non aqueous, polar solvents. Specifically, solutions of lithium hexafluorophosphate in propylene carbonate and dimethoxyethane serve as an electrolyte in lithium batteries. This application also exploits the inertness of the hexafluorophosphate anion toward strong reducing agents, such as lithium metal. The salt is relatively stable thermally, but loses 50% weight at 200 °C (392 °F). It hydrolyzes near 70 °C (158 °F) according to the following equation: Owing

neg: Tetrakis(acetonitrile)copper(I) hexafluorophosphate be displaced in other solvents, the [Cu(CHCN)]PF compound may serve as a precursor in the non-aqueous syntheses of other Cu(I) compounds. Water-immiscible organic nitriles have been shown to selectively extract Cu(I) from aqueous chloride solutions. Through this method, copper can be separated from a mixture of other metals. Dilution of acetonitrile solutions with water induces disproportionation: Tetrakis(acetonitrile)copper(I) hexafluorophosphate Tetrakis(acetonitrile)copper(I) hexafluorophosphate is a coordination compound with the formula [Cu(CHCN)]PF. It is a colourless solid that is used in the synthesis of other copper complexes. It is a well-known example of a transition metal nitrile complex. As confirmed by X-ray crystallographic studies,

neg: Rhodocene the analogous iridium synthesis is also known. Decaisopropylrhodicnium hexafluorophosphate was synthesised in 1,2-dimethoxyethane (solvent) in an unusual one-pot synthesis that involves the formation of 20 carbon–carbon bonds: In a similar reaction, pentaisopropylrhodocenium hexafluorophosphate [(η-CPr)Rh(η-CH)]PF can be synthesised from pentamethylrhodocenium hexafluorophosphate [(η-CMe)Rh(η-CH)]PF in 80% yield. These reactions demonstrate that the acidity of the methyl hydrogens in a pentamethylcyclopentadienyl complex can be considerably increased by the presence of the metal centre. Mechanistically, the reaction proceeds with potassium hydroxide deprotonating a methyl group and the resulting carbanion undergoing nucleophilic substitution with methyl iodide to form a new carbon–carbon bond. The compounds pentaphenylrhodocenium tetrafluoroborate

neg: Ferrocenium tetrafluoroborate Ferrocenium tetrafluoroborate Ferrocenium tetrafluoroborate is an organometallic compound with the formula [Fe(CH)]BF. This salt is composed of the cation [Fe(CH)] and the tetrafluoroborate anion (). The related hexafluorophosphate is also a popular reagent with similar properties. The cation is often abbreviated Fc or CpFe. The salt is deep blue in color and paramagnetic. Ferrocenium salts are sometimes used as one-electron oxidizing agents, and the reduced product, ferrocene, is inert and readily separated from ionic products. The ferrocene–ferrocenium couple is often used as a reference in electrochemistry. The standard potential of ferrocene-ferrocenium is 0.400 V vs. the normal hydrogen electrode (NHE)

neg: Carbanion Carbanion A carbanion is an anion in which carbon is trivalent (forms three bonds) and bears a formal negative charge in at least one significant mesomeric contributor (resonance form). Absent π delocalization, carbanions assume a trigonal pyramidal, bent, or linear geometry when the carbanionic carbon is bound to three (e.g., methyl anion), two (e.g., phenyl anion), or one (e.g., acetylide anion) substituents, respectively. Formally, a carbanion is the conjugate base of a carbon acid: where B stands for the base. Carbanions have a concentration of electron density at the negatively charged carbon, which, in most cases, reacts efficiently with a

neg: Peter Maitlis the Royal Society in 1984. The citation highlights his work on the platinum group metals palladium, rhodium and iridium. The hexafluorophosphate ion is generally considered inert and hence a suitable counterion in organometallic synthesis. However, Maitlis' work has demonstrated a solvolysis reaction of the hexafluorophosphate ion. The tris(solvent) rhodium complex [(η-CMe)Rh(MeCO)](PF) undergoes solvolysis when heated in acetone, forming a difluorophosphate-bridged complex [(η-CMe)Rh(μ-OPFO)Rh(η-CMe)]PF. Hexamethyl Dewar benzene (CMe) undergoes an unusual rearrangement reaction with hydrohalic acids to form a pentamethylcyclopentadiene derivative, and consequently can be used as a starting material for synthesising some pentamethylcyclopentadienyl organometallic compounds. Maitlis and colleagues demonstrated this synthesis

neg: Triphenylmethyl hexafluorophosphate triphenylmethyl hexafluorophosphate. However, the perchlorate is not used as widely, because, like other organic perchlorates, it is potentially explosive. Triarylmethane dyes are derivatives are stabilized version of the trityl cation, so much so that they are water-soluble and are often obtained as the chloride salts. These dyes have strong electron donor groups, often amines, at the "p"-positions of two or three of the aryl groups. Triphenylmethyl hexafluorophosphate Triphenylmethyl hexafluorophosphate is an organic salt with the formula (CH)CPF. It is a brown powder that hydrolyzes readily to triphenylmethanol. Triphenylmethyl hexafluorophosphate is used as a catalyst and reagent in organic syntheses. Triphenylmethyl

neg: Carbenium ion each of the three phenyl groups, plus the central carbon atom). It exists in the compounds triphenylmethyl hexafluorophosphate (C(CH)PF) and triphenylmethyl perchlorate (C(CH)ClO). Triphenylmethyl hexafluorophosphate is used as a catalyst and reagent in organic syntheses; it is generated by combining silver hexafluorophosphate with triphenylmethyl chloride: These and other similar cations can be obtained as intensely colored solutions by dissolving aryl-substituted methanols in concentrated sulfuric acid. An arenium ion is a cyclohexadienyl cation that appears as a reactive intermediate in electrophilic aromatic substitution. For historic reasons this complex is also called a "Wheland intermediate", or a "σ-complex". Two hydrogen atoms bonded

neg: VSEPR theory that the decrease in the bond angle in the series (180°), NO (134°), (115°) indicates that a given set of bonding electron pairs exert a weaker repulsion on a single non-bonding electron than on a pair of non-bonding electrons. In effect, they considered nitrogen dioxide as an AXE molecule, with a geometry intermediate between and . Similarly, chlorine dioxide (ClO) is an AXE molecule, with a geometry intermediate between and . Finally, the methyl radical (CH) is predicted to be trigonal pyramidal like the methyl anion (), but with a larger bond angle (as in the trigonal planar methyl cation

neg: Hypervalent molecule electron density from the central atom so that its net content is again 8 electrons or fewer. Consistent with this alternative view is the finding that hypercoordinated molecules based on fluorine ligands, for example PF do not have hydride counterparts e.g. phosphorane PH which is unknown. The ionic model holds up well in thermochemical calculations. It predicts favorable exothermic formation of PFF from phosphorus trifluoride PF and fluorine F whereas a similar reaction forming PHH is not favorable. Durrant has proposed an alternative definition of hypervalency, based on the analysis of atomic charge maps obtained from Atoms in molecules theory.

neg: Phosphotungstic acid Phosphotungstic acid is electron dense, opaque for electrons. It is a common negative stain for viruses, nerves, polysaccharides, and other biological tissue materials for imaging by a transmission electron microscope. Gouzerh summarises the historical views on the structure of phosphotungstic acid leading up to Keggin's determination of the structure as: The structure was determined by J.F Keggin first published in 1933 and then in 1934 and is generally known as the Keggin structure. The anion has full tetrahedral symmetry and comprises a cage of twelve tungsten atoms linked by oxygen atoms with the phosphorus atom at its centre. The picture

neg: Phosphorus pentafluoride low as −100 °C, fails to distinguish the axial from the equatorial fluorine environments. The apparent equivalency arises from the low barrier for pseudorotation via the Berry mechanism, by which the axial and equatorial fluorine atoms rapidly exchange positions. The apparent equivalency of the F centers in PF was first noted by Gutowsky. The explanation was first described by R. Stephen Berry, after whom the Berry mechanism is named. Berry pseudorotation influences the F NMR spectrum of PF since NMR spectroscopy operates on a millisecond timescale. Electron diffraction and X-ray crystallography do not detect this effect as the solid state

neg: Valence electron are those whose average distance from the nucleus is greatest; that is, those with the highest energy. For a main group element, the valence electrons are defined as those electrons residing in the electronic shell of highest principal quantum number n. Thus, the number of valence electrons that it may have depends on the electron configuration in a simple way. For example, the electronic configuration of phosphorus (P) is 1s 2s 2p 3s 3p so that there are 5 valence electrons (3s 3p), corresponding to a maximum valence for P of 5 as in the molecule PF; this configuration is

neg: Phosphorus trifluoride for which the corresponding CO derivatives (see metal carbonyl) are unstable or nonexistent. Thus, Pd(PF) is known, but Pd(CO) is not. Such complexes are usually prepared directly from the related metal carbonyl compound, with loss of CO. However, Nickel metal reacts directly with PF at 100 °C under 35 MPa pressure to form Ni(PF), which is analogous to Ni(CO). Cr(PF), the analogue of Cr(CO), may be prepared from dibenzenechromium: Phosphorus trifluoride is usually prepared from phosphorus trichloride via halogen exchange using various fluorides such as hydrogen fluoride, calcium fluoride, arsenic trifluoride, antimony trifluoride, or zinc fluoride: Phosphorus trifluoride is similar

neg: Plumbylene intramolecular rearrangement to place more electron-donating heteroatoms next to the electron-deficient lead. Plumbylenes are known to undergo nucleophilic substitution with organometallic reagents to form transmetallated products. In an unusual example, the use of TlPF, bearing the weakly coordinating anion PF, led to the formation of crystals of an oligonuclear lead compound with a chain structure upon work-up, highlighting the interesting reactivity of plumbylenes. In addition, plumbylenes can also undergo metathesis with group 13 E(CH) (E = Al, Ga) compounds. Plumbylenes bearing different substituents can also undergo transmetallation and exchange substituents, with the driving force being the relief of steric strain

neg: Trigonal bipyramidal molecular geometry positions only and the three equatorial positions filled with lone pairs of electrons (AXE). Isomers with a trigonal bipyramidal geometry are able to interconvert through a process known as Berry pseudorotation. Pseudorotation is similar in concept to the movement of a conformational diastereomer, though no full revolutions are completed. In the process of pseudorotation, two equatorial ligands (both of which have a shorter bond length than the third) "shift" toward the molecule's axis, while the axial ligands simultaneously "shift" toward the equator, creating a constant cyclical movement. Pseudorotation is particularly notable in simple molecules such as phosphorus pentafluoride (PF). Trigonal

neg: Electron capture ionization In contrast to electron ionization, EC-MS uses low energy electrons in a gas discharge. EC-MS will cause less fragmentation of molecules compared to electron ionization. Resonance electron capture is also known as nondissociative EC. The compound attaches an electron to form a radical anion. The energy of the electrons are about 0 eV. The electrons can be created in the Electron Ionization source with moderating gas such as H, CH, i-CH, NH, N, and Ar. After the ion captures the electron, the complex formed can stabilize during collisions and produce a stable anion that can be detected in a mass

neg: Phosphorus pentachloride with organic compounds, the use of PCl has been superseded by SOCl. The reaction of phosphorus pentoxide and PCl produces POCl: PCl chlorinates nitrogen dioxide to form unstable nitryl chloride: PCl is a precursor for lithium hexafluorophosphate, LiPF, an electrolyte in lithium ion batteries. is produced by the reaction of with lithium fluoride, with lithium chloride as a side product: PCl is a dangerous substance as it reacts violently with water. Phosphorus pentachloride was first prepared in 1808 by the English chemist Humphry Davy. Davy's analysis of phosphorus pentachloride was inaccurate; the first accurate analysis was provided in 1816 by

neg: Rhodocene has been shown to involve a loss of one electron from the pentadienediyl ligand followed by a fast rearrangement (with loss of a hydrogen atom) to form the 1,2,3-tri-"tert"-butylrhodocenium cation. Both the tetrafluoroborate and hexafluorophosphate salts of this cation have been structurally characterised by X-ray crystallography. [(η-CBuH)Rh(η-CH)]BF forms a colourless centrosymmetric monoclinic crystal belonging to the "P"2/c space group, and with a density of 1.486 g cm. Looking at the ORTEP diagram of the structure of the cation (at right), it is evident that it possesses the typical geometry expected of a rhodocene or rhodocenium cation. The two cyclopentadienyl rings

neg: Phosphorus trifluoride of HPO). Phosphorus trifluoride hydrolyzes especially at high pH, but it is less hydrolytically sensitive than phosphorus trichloride. It does not attack glass except at high temperatures, and anhydrous potassium hydroxide may be used to dry it with little loss. With hot metals, phosphides and fluorides are formed. With Lewis bases such as ammonia addition products (adducts) are formed, and PF is oxidized by oxidizing agents such as bromine or potassium permanganate. As a ligand for transition metals, PF is a strong π-acceptor. It forms a variety of metal complexes with metals in low oxidation states. PF forms several complexes

neg: Hydrogen anion Hydrogen anion The hydrogen anion, H, is a negative ion of hydrogen, that is, a hydrogen atom that has captured an extra electron. The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is called hydride. The ion has two electrons bound by the electromagnetic force to a nucleus containing one proton. The binding energy of H equals the binding energy of an extra electron to a hydrogen atom, called electron affinity of hydrogen. It is measured to be or (see Electron affinity (data page)). The total ground state energy

neg: Phosphaethynolate the anion means that it is able to bind via both the phosphorus and oxygen atoms depending on the nature of the centre being coordinated. Computational studies carried out on the anion such as Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) analyses can go part way to explain why PCO can react in such a manner "(see Figure 1)". The two dominant resonance forms of the phosphaethynolate anion localise negative charge on either the phosphorus or oxygen atoms meaning both are sites of nucleophilicity. The same applies for the cyanate anion hence why PCO is observed to have

neg: Phosphorus trifluoride Phosphorus trifluoride Phosphorus trifluoride (formula PF), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand, it parallels carbon monoxide in metal carbonyls, and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide. Phosphorus trifluoride has an F−P−F bond angle of approximately 96.3°. Gaseous PF has a standard enthalpy of formation of −945 kJ/mol (−226 kcal/mol). The phosphorus atom has a nuclear magnetic resonance chemical shift of 97 ppm (downfield

neg: Non-coordinating anion to catalyze hydrogenation, hydrosilylation, oligomerization, and the living polymerization of olefins. The popularization of non-coordinating anions has contributed to increased understanding of agostic complexes wherein hydrocarbons and hydrogen serve as ligands. Non-coordinating anions are important components of many superacids, which result from the combination of Brønsted acids and Lewis acids. Prior to the 1990s, tetrafluoroborate (), hexafluorophosphate (), and perchlorate () were considered weakly coordinating anions. These species are now known to bind to strongly electrophilic metal centers. Tetrafluoroborate and hexafluorophosphate anions are coordinating toward highly electrophilic metal ions, such as cations containing Zr(IV) centers, which can abstract fluoride from

neg: Phosphaethynolate anion and ammonium salts which yielded the phosphorus containing analogue of urea in which phosphorus replaces a nitrogen atom. The group predict that this heavier congener could have applications in new materials, anion sensing and coordination chemistry. Goicoechea and co-workers were also able to isolate the heavily sought after phosphorus containing analogue of isocyanic acid, HPCO, in 2017. This molecule is thought to be a crucial intermediate in a lot of reactions involving PCO "(including P-transfer to an imidazolium cation; see above)". Moreover, the most recent addition to this class of small molecules is the phosphorus containing analogue of N,N-dimethylformamide.

neg: Trigonal bipyramidal molecular geometry be longer because the ligand atom cannot approach the central atom as closely. As examples, in PF the axial P−F bond length is 158 pm and the equatorial is 152 pm, and in PCl the axial and equatorial are 214 and 202 pm respectively. In the mixed halide PFCl the chlorines occupy two of the equatorial positions, indicating that fluorine has a greater apicophilicity or tendency to occupy an axial position. In general ligand apicophilicity increases with electronegativity and also with pi-electron withdrawing ability, as in the sequence Cl < F < CN. Both factors decrease electron density in the

neg: Phosphorus trifluoride to carbon monoxide in that it is a gas which strongly binds to iron in hemoglobin, preventing the blood from absorbing oxygen. PF is highly toxic, comparable to phosgene. Phosphorus trifluoride Phosphorus trifluoride (formula PF), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand, it parallels carbon monoxide in metal carbonyls, and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide. Phosphorus trifluoride has an F−P−F bond angle of

neg: Non-coordinating anion these anions. Other anions, such as triflates are considered to be low-coordinating with some cations. A revolution in this area occurred in the 1990s with the introduction of the tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion, , commonly abbreviated as and colloquially called "BARF". This anion is far less coordinating than tetrafluoroborate, hexafluorophosphate, and perchlorate, and consequently has enabled the study of still more electrophilic cations. Related tetrahedral anions include tetrakis(pentafluorophenyl)borate , and . In the bulky borates and aluminates, the negative charge is symmetrically distributed over many electronegative atoms. Related anions are derived from tris(pentafluorophenyl)boron B(CF). Another advantage of these anions is that their

neg: Phosphorus thought that bonding in phosphorus(V) compounds involved "d" orbitals. Computer modeling of molecular orbital theory indicates that this bonding involves only s- and p-orbitals. All four symmetrical trihalides are well known: gaseous PF, the yellowish liquids PCl and PBr, and the solid PI. These materials are moisture sensitive, hydrolysing to give phosphorous acid. The trichloride, a common reagent, is produced by chlorination of white phosphorus: The trifluoride is produced from the trichloride by halide exchange. PF is toxic because it binds to haemoglobin. Phosphorus(III) oxide, PO (also called tetraphosphorus hexoxide) is the anhydride of P(OH), the minor tautomer of phosphorous

neg: Superoxide Superoxide A superoxide is a compound that contains the superoxide anion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen anion superoxide is particularly important as the product of the one-electron reduction of dioxygen O, which occurs widely in nature. Molecular oxygen (dioxygen) is a diradical containing two unpaired electrons, and superoxide results from the addition of an electron which fills one of the two degenerate molecular orbitals, leaving a charged ionic species with a single unpaired electron and a net negative charge of −1. Both dioxygen and the superoxide anion are

neg: Active site fluorophosphate(DIFP) is an irreversible inhibitor that blocks the action of serine protease. When it binds to the enzyme a nucleophilic substitution reaction occurs and releases one hydrogen fluoride molecule. The OH group in active site acts as a nucleophile to attack the phosphorus in DIFP and form a tetrahedral intermediate and release a proton. Then the P-F bond is broken, one electron is transferred to the F atom and it leaves the intermediate as F anion. It combines with a proton in solution to form one HF molecule. Now there is a covalent bond formed between the active site and

neg: Azulene by Placidus Plattner. Azulene is usually viewed as resulting from fusion of cyclopentadiene and cycloheptatriene rings. Like naphthalene and cyclodecapentaene, it is a 10 pi electron system. It exhibits aromatic properties: (i) the peripheral bonds have similar lengths and (ii) it undergoes Friedel-Crafts-like substitutions. The stability gain from aromaticity is estimated to be half that of naphthalene. Its dipole moment is 1.08 D, in contrast with naphthalene, which has a dipole moment of zero. This polarity can be explained by regarding azulene as the fusion of a 6 π-electron cyclopentadienyl anion and a 6 π-electron tropylium cation: one electron from

neg: Van der Waals strain potential energy, even between molecules with identical geometry. PF, for example, has significantly lower potential energy than PCl. Despite their identical trigonal bipyramidal molecular geometry, the higher electron count of chlorine as compared to fluorine causes a potential energy spike as the molecule enters its intermediate in the mechanism and the substituents draw nearer to each other. Van der Waals strain In chemistry, van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. Van der Waals

neg: Silver perchlorate and toluene (1010 g/L). In these solvents, the silver cation binds to the arene, as has been demonstrated by extensive crystallographic studies on crystals obtained from such solutions. It is also amazingly soluble in water, up to 500 g per 100 mL of water. Similar to silver nitrate, silver perchlorate is an effective reagent for replacing halides ligands with perchlorate, which is a weakly or non-coordinating anion. The use of silver perchlorate in chemical synthesis has declined due to concerns about explosiveness of perchlorate salts. Other silver reagents are silver tetrafluoroborate, and the related silver trifluoromethanesulfonate and silver hexafluorophosphate. Silver

neg: Phosphaethynolate is formed by oxygen coordination. The oxygen atom favours a larger degree of ionic interactions as a result of its greater electronegativity. Contrastingly, the thermodynamic product of the reaction is generated under orbital control. This comes in the form of phosphorus coordination as the largest contribution in the HOMO of the anion resides on the phosphorus atom; this is clearly visible in "Figure 3". Extensive studies involving the phosphaethynolate anion have shown that it can react in a variety of ways. It has documented use in cycloadditions, as a phosphorus transfer agent, a synthetic building block and as pseudo halide

neg: One-electron reduction from alkyl halides such as 5-chloromethyl-6-nitrobenzo[1,3]dioxole: The one-electron reduction potential of a molecule can be used to obtain an electron affinity. For example: The one-electron reduction potential of molecular oxygen gives a value of 1.07(1) eV. Recently, photoredox catalysis has become a very common way to engage in single electron reduction. One-electron reduction A one-electron reduction in organic chemistry involves the transfer of an electron from a donor compound to an organic substrate. It serves to differentiate between two electron organic reductions such as hydride transfer reactions. The first intermediate in a one-electron reduction is often a radical anion, which

neg: Molybdenum blue the anion is termed the heteroatom, other heteroatoms are silicon and arsenic. The heteropoly-molybdenum blues have structures based on the Keggin structure. The blue colour arises because the near-colourless anion, such as the phosphomolybdate anion, , can accept more electrons (i.e. be reduced) to form an intensely coloured mixed-valence complex. This can occur in one electron or two electron steps. The reduction process is reversible and the structure of the anion is essentially unchanged. The structure of the anion, PMoMo, has been determined in the solid state and is a β-isomer (i.e. with one of the four groups of edge-shared

neg: Rieske protein plants, catalyses the oxidoreduction of plastoquinol and cytochrome f. This complex, which is functionally similar to ubiquinol-cytochrome c reductase, comprises cytochrome b6, cytochrome f and Rieske subunits. The Rieske subunit acts by binding either a ubiquinol or plastoquinol anion, transferring an electron to the 2Fe-2S cluster, then releasing the electron to the cytochrome c or cytochrome f heme iron. The reduction of the Rieske center increases the affinity of the subunit by several orders of magnitude, stabilizing the semiquinone radical at the Q(P) site. The Rieske domain has a [2Fe-2S] center. Two conserved cysteines coordinate one Fe ion while the

neg: Reactive oxygen species production in marine microalgae molecular oxygen are what are referred to as reactive oxygen species. Thus, the production of ROS is in direct proportion to the concentration of O in the system, with increases of O leading to higher production of ROS. There are three main reactive oxygen species: the superoxide anion (O), hydrogen peroxide (HO), and the hydroxyl radical (OH•). The superoxide anion is formed directly from the one-electron reduction of molecular oxygen. Hydrogen peroxide is then formed from the disproportionation of the superoxide anion. This reaction occurs very quickly in seawater. Next, the reduction of hydrogen peroxide yields the hydroxyl radical, HO↔2OH•,

neg: Fluxional molecule η-C"H". The singlet assigned to the η-CH ligand splits at low temperatures owing to the slow hopping of the Fe center from carbon to carbon in the η-CH ligand. Two mechanisms have been proposed, with the consensus favoring the 1,2 shift pathway. Pentacoordinate molecules of trigonal pyramidal geometry typically exhibit a particular kind of low energy fluxional behavior called Berry pseudorotation. Famous examples of such molecules are iron pentacarbonyl (Fe(CO)) and phosphorus pentafluoride (PF). At higher temperatures, only one signal is observed for the ligands (e.g., by C or F NMR) whereas at low temperatures, two signals in a 2:3

neg: One-electron reduction One-electron reduction A one-electron reduction in organic chemistry involves the transfer of an electron from a donor compound to an organic substrate. It serves to differentiate between two electron organic reductions such as hydride transfer reactions. The first intermediate in a one-electron reduction is often a radical anion, which then engages in secondary reactions. In the Birch reduction, the secondary reaction is proton abstraction from an alcohol. This reaction type is also called a dissolving metal reduction. Alkyne reduction to an alkene in the liquid ammonia/sodium system follows the same theme. The first radical anion intermediate abstracts a proton from

neg: Phosphaethynolate ligands "(as described above)". In these types of reactions, CO is released as the phosphaethynolate anion acts as either a mild nucleophilic source of phosphorus or a Brønsted base. Examples of these types of reactions involving PCO include work conducted by Grutzmacher and Goicoechea. In 2014, Grutzmacher et al. reported that an imidazolium salt would react with the phosphaethynolate anion to produce a phosphinidine carbene adduct. Computational mechanistic studies were conducted on this reaction using density functional theory at the B3LYP/6-31+G* level. The results of these investigations eluded to the fact that the lowest energy and therefore most likely pathway

neg: Boron trifluoride Boron trifluoride Boron trifluoride is the inorganic compound with the formula BF. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. The geometry of a molecule of BF is trigonal planar. Its D symmetry conforms with the prediction of VSEPR theory. The molecule has no dipole moment by virtue of its high symmetry. The molecule is isoelectronic with the carbonate anion, CO. BF is commonly referred to as "electron deficient," a description that is reinforced by its exothermic reactivity toward Lewis bases. In

neg: Solvated electron a common species, the solvated electron. In the 1970s, solid salts containing electrons as the anion were characterized. Solvated electron A solvated electron is a free electron in (solvated in) a solution, and is the smallest possible anion. Solvated electrons occur widely, although it is difficult to observe them directly since their lifetimes are so short. The deep color of solutions of alkali metals in ammonia arises from the presence of solvated electrons: blue when dilute and copper-colored when more concentrated (> 3 molar). Classically, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days,

neg: Superoxide leaving a charged ionic species with single unpaired electron and a net negative charge of −1. Both dioxygen and the superoxide anion are free radicals that exhibit paramagnetism. The derivatives of dioxygen have characteristic O–O distances that correlate with the order of the O–O bond. Superoxide A superoxide is a compound that contains the superoxide anion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen anion superoxide is particularly important as the product of the one-electron reduction of dioxygen O, which occurs widely in nature. Molecular oxygen (dioxygen) is a diradical containing

neg: Pi interaction in the case of the 18-electron Pd complex. The authors of this research proposed that when the olefin π bond is aligned on the side of the square planar Pd complex, the π* backfilling of electron density from Pd to olefin is enhanced because the more electron withdrawing orbital of the π complex can overlap better with the electron donating orbital of Pd. Anion and π-aromatic systems (typically electron deficient) create an interaction that is associated with the repulsive forces of the structures. These repulsive forces involve electrostatic and anion-induced polarized interactions. This force allows for the systems to be

neg: Ion attain this stable configuration, becoming a sodium cation in the process On the other hand, a chlorine atom, Cl, has 7 electrons in its valence shell, which is one short of the stable, filled shell with 8 electrons. Thus, a chlorine atom tends to "gain" an extra electron and attain a stable 8-electron configuration, becoming a chloride anion in the process: This driving force is what causes sodium and chlorine to undergo a chemical reaction, wherein the "extra" electron is transferred from sodium to chlorine, forming sodium cations and chloride anions. Being oppositely charged, these cations and anions form ionic

neg: Photoelectrochemical reduction of CO2 CO is the large reorganization energy between the linear molecule and bent radical anion. Proton-coupled multi-electron steps for CO reductions are generally more favorable than single electron reductions, as thermodynamically more stable molecules are produced. Thermodynamically, proton coupled multiple-electron reduction of CO is easier than single electron reduction. But to manage multiple proton coupled multiple-electron processes is a huge challenge kinetically. This leads to a high overpotential for electrochemical heterogeneous reduction of CO to hydrocarbons and alcohols. Even further heterogeneous reduction of singly reduced CO radical anion is difficult because of repulsive interaction between negatively biased electrode and negatively charged

neg: Sodium monofluorophosphate of the fluorophosphate anion consists of phosphorus at the center of a tetrahedron defined by three oxygen atoms and one fluorine. Formal representations depict a double bond between one oxygen atom and phosphorus, with single bonds for the other two oxygen atoms and the fluorine. In this very formal depiction, negative charge is localized on the O atoms of the single P-O bonds. MFP is similar to and isoelectronic with NaSO. The anion has C symmetry. Sodium monofluorophosphate was first described in 1929 by the German chemist Willy Lange, who was then with the University of Berlin. His fruitless attempts

neg: Phosphorus tribromide Phosphorus tribromide Phosphorus tribromide is a colourless liquid with the formula PBr. It is a colourless liquid that fumes in moist air due to hydrolysis and has a penetrating odour. It is used in the laboratory for the conversion of alcohols to alkyl bromides. PBr is prepared by treating red phosphorus with bromine. An excess of phosphorus is used in order to prevent formation of PBr: Because the reaction is highly exothermic, it is often conducted in the presence of a diluent such as PBr. Phosphorus tribromide, like PCl and PF, has both properties of a Lewis base and a

neg: Inert pair effect the s electron lone pair has little or no influence on the geometry of the molecule or crystal). A simple example of steric activity is that of SnCl which is bent in accordance with VSEPR. Some examples where the lone pair appears to be inactive are bismuth(III) iodide, BiI, and the anion. In both of these the central Bi atom is octahedrally coordinated with little or no distortion, in contravention to VSEPR theory. The steric activity of the lone pair has long been assumed to be due to the orbital having some p character, i.e. the orbital is not spherically

neg: Corannulene groups. The observed aromaticity for this compound is explained with a so-called annulene-within-an-annulene model. According to this model corannulene is made up of an aromatic 6 electron cyclopentadienyl anion surrounded by an aromatic 14 electron annulenyl cation. This model was suggested by Barth and Lawton in the first synthesis of corannulene in 1966. They also suggested the trivial name 'corannulene', which is derived from the annulene-within-an-annulene model: core + annulene. However, later theoretical calculations have disputed the validity of this approximation. Corannulene can be reduced up to a tetraanion in a series of one-electron reductions. This has been performed with

neg: Hydrogen ion connection with acids, "hydrogen ions" typically refers to hydrons. "Hydrogen atom (center) contains a single proton and a single electron. Removal of the electron gives a cation (left), whereas addition of an electron gives an anion (right). The hydrogen anion, with its loosely held two-electron cloud, has a larger radius than the neutral atom, which in turn is much larger than the bare proton of the cation. Hydrogen forms the only cation that has no electrons, but even cations that (unlike hydrogen) still retain one or more electrons are still smaller than the neutral atoms or molecules from which they

neg: Kimberly Renee Dunbar metal bonded system and conciliation by interactions in anions and aromatic ligands in supramolecular structures and properties allowed her to focus on interfaced problems of metal-based drugs in medicine, alongside synthetic challenges in biological chemistry such as supramolecular anion-𝝅 interactions. Professor Dunbar has extensively studied anion-𝝅 interactions, which describe the special relationship between aromatic molecules and anions. Aromatic systems normally have a high level of electron density and would repel negatively charged particles, however electron deficient ring systems specifically are able to accept the electron density of anions to form a non-covalent interaction. Some important applications of the anion-𝝅 interactions

neg: Crystallographic defects in diamond ultraviolet light. Apart from optical absorption, boron acceptors have been detected by electron paramagnetic resonance. Phosphorus could be intentionally introduced into diamond grown by chemical vapor deposition (CVD) at concentrations up to ~0.01%. Phosphorus substitutes carbon in the diamond lattice. Similar to nitrogen, phosphorus has one more electron than carbon and thus acts as a donor; however, the ionization energy of phosphorus (0.6 eV) is much smaller than that of nitrogen (1.7 eV) and is small enough for room-temperature thermal ionization. This important property of phosphorus in diamond favors electronic applications, such as UV light emitting diodes (LEDs, at 235

neg: D electron count formal oxidation state and d electron count can still be useful when trying to understand the chemistry. There are many examples of every possible d electron configuration. What follows is a short description of common geometries and characteristics of each possible d electron count and representative examples. D electron count The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. The d electron count is an effective way to understand the geometry and reactivity of transition metal complexes. The formalism has been incorporated

neg: Reductive dehalogenation of halo ketones the nature of the reducing agent. One-electron reducing agents, such as "d" or "d" transition metal complexes, initially donate a single electron to the halo ketone. Fragmentation of the resulting radical anion yields an organic radical and halide anion. Donation of a second electron from a "second equivalent" of reducing agent leads to the formation of a metal enolate in which the oxidation state of the reducing agent has increased by one. Two-electron reducing agents, the most prominent of which is zinc metal, undergo direct oxidative addition to monohalo ketones to afford metal enolates in which the oxidation state of

neg: Phosphenium backbonding, though the phosphenium was observed to have reduced σ donor ability. It was suggested that this is due to the greater s orbital-character of the phosphorus lone pair compared to the lone pair of the analogous carbene. Additional studies of NHP ligands by Christine Thomas and coworkers in 2012, likened the phosphenium to nitrosyl. Nitrosyl is well known for its redox non-innocence, coordinating in either a bent or linear geometry that possess different L-M bonding modes. It was observed that NHPs in complex with a transition metal may have either a planar or pyramidal geometry about the phosphorus, reminiscent

neg: Anionic addition polymerization type of initiation both for stability of the anion-radical and to solvate the cation species formed. The anion-radical can then transfer an electron to the monomer. Initiation can also involve the transfer of an electron from the alkali metal to the monomer to form an anion-radical. Initiation occurs on the surface of the metal, with the reversible transfer of an electron to the adsorbed monomer. Nucleophilic initiators include covalent or ionic metal amides, alkoxides, hydroxides, cyanides, phosphines, amines and organometallic compounds (alkyllithium compounds and Grignard reagents). The initiation process involves the addition of a neutral (B:) or negative (B:-) nucleophile

neg: Organoboron chemistry low electronegativity of boron. Reaction of base with a borohydride RBH does not result in deprotonation to the boryl anion RB but to formation of the boryl anion RBH(base). This reaction product has a complete octet. Instead the boryl compound is prepared by reductive heterolysis of a boron-bromide bond by lithium metal. The new boryl lithium compound is very similar to and isoelectronic with N-heterocyclic carbenes. It is designed to benefit from aromatic stabilization (6-electron system counting the nitrogen lone pairs and an empty boron p-orbital, see structure A) and from kinetic stabilization from the bulky 2,6-diisopropylphenyl groups. X-ray diffraction

neg: Barium ferrate Barium ferrate Barium ferrate is the chemical compound of formula BaFeO. This is a rare compound containing iron in the +6 oxidation state. The ferrate(VI) ion has two unpaired electrons, making it paramagnetic. It is isostructural with BaSO, and contains the tetrahedral <nowiki>[</nowiki>FeO<nowiki>]</nowiki> anion. The ferrate(VI) anion is paramagnetic due to its two unpaired electrons and it has a tetrahedral molecular geometry. X-ray diffraction has been used to determine the orthorhombic unit cell structure (lattice vectors a ≠ b ≠ c, interaxial angles α=β=γ=90°) of nanocrystalline BaFeO. It has a pnma space group (point group: D) with lattice parameters "a"=0.8880

neg: Monofluorophosphate Monofluorophosphate Monofluorophosphate is an anion with the formula POF, which is a phosphate group with one oxygen atom substituted with a fluoride atom. The charge of the ion is −2. The ion resembles sulfate in size, shape and charge, and can thus form compounds with the same structure as sulfates. These include Tutton's salts and langbeinites. The most well-known compound of monofluorophosphate is sodium monofluorophosphate, commonly used in toothpaste. Related ions include difluorophosphate () and hexafluorophosphate (). The related neutral molecule is phosphenic fluoride POF. Organic derivatives can be highly toxic and include diisopropyl fluorophosphate. Some of the Novichok agents

neg: Dewar benzene + 1 = 3.7 < 4, and thus the species is not hypervalent, but it is hypercoordinate. From the perspective of organometallic chemistry, the species can be viewed as having a carbon(IV) centre () bound to an aromatic anion (six-electron donor) and a methyl anion (two-electron donor), thereby satisfying the octet rule and being analogous to the gas-phase organozinc monomer which has the same ligands bound to a zinc(II) centre () and satisfies the 18 electron rule on the metal. Thus, while unprecedented, and having attracted comment in "Chemical & Engineering News", "New Scientist", "Science News", and ZME Science, the

neg: William Stanley Jevons had no effect on the truth of these axioms. Jevons hence makes the distinction between truth and applicability or perception, suggesting that these concepts were independent in the domain of geometry. Jevons did not claim that geometry was developed without any consideration for spatial reality. Instead, he suggested that his geometric systems were representations of reality but in a more fundamental way that transcends what one can perceive about reality. Jevons claimed that there was a flaw in Helmholtz's argument relating to the concept of infinitesimally small. This concept involves how these creatures reason about geometry and space at a

neg: High-field domain as it varies depending on external parameters. As an example, it can be shown that it depends on the optical excitation in a photoconductor (See Fig. 5). High-field domains as tools to measure the electron density in the field quenched branch and of the electron mobility as a function of the temperature The high-field domain is determined by the boundary density at the cathode and the field within the domain. A shadow band in front of the cathode acts as a pseudo-cathode, as it reduces the electron density within the shadow (Fig. 6). This can be used as an experimental

neg: Radical-nucleophilic aromatic substitution aliphatic SN1 reaction. An example of this reaction type is the Sandmeyer reaction. In this radical substitution the aryl halide 1 accepts an electron from an radical initiator forming a radical anion 2. This intermediate collapses into an aryl radical 3 and a halide anion. The aryl radical reacts with the nucleophile 4 to a new radical anion 5 which goes on to form the substituted product by transferring its electron to new aryl halide in the chain propagation. Alternatively the phenyl radical can abstract any loose proton from 7 forming the arene 8 in a chain termination reaction. The

neg: Phosphaethynolate double bond of cyclotrisilene thus introducing a phosphorus vertex into its scaffold (after undergoing decarbonylation). After synthesising the potassium salt of the phosphaethynolate anion in 2013 "(see above)", Goicoechea et al. began to look into the potential of PCO towards cycloadditions. They found that the anion could react in a [2+2] fashion with a diphenyl ketene to produce the first isolatable example of a four-membered monoanionic phosphorus containing heterocycle. They employed the same method to test other unsaturated substrates such as carbodiimides and found that the likelihood of cyclisation heavily relies on the nature of the substituents on the unsaturated