Fluorine valency states

Replacement of Hydrogen. Three methods of substitution of a hydrogen atom by fluorine are (/) reaction of a G—H bond with elemental fluorine (direct fluorination, (2) reaction of a G—H bond with a high valence state metal fluoride like Agp2 or GoF, and (J) electrochemical fluorination in which the reaction occurs at the anode of a cell containing a source of fluoride, usually HF. 

Xenon is noncombustible, and even though it is considered inert, it will combine with a few elements (i.e., oxygen, fluorine, and platinum). Xenon is the only member of group 18 that exhibits all of the even valence states of +2, +4, +6, and +8. It has similar oxidation states even though most periodic tables list a single oxidation state of zero. 

In this paper only the aspects of structural chemistry of the more common structure types adapted by fluorine compounds will be considered. There wiU also be a brief account of the cooperative phenomena of antiferro- and ferrimagnetism, that are strongly dependent on crystal structures. For all information on preparation and chemical properties of transition metal fluorocomplexes, especicilly interesting for the high valency states, the reader is referred to the excellent reviews given by Sharpe (278) and by Peacock (255). 

Sulfur is oxidatively fluorinated up to its highest valence state, six. For instance, alkyl thiols give perfluoroalkyl-sulfurpentafluorides (Fig. 40) [104] and sulfides give perfluorodialkyl-sulfurtetrafluorides (Fig. 41) [105,106]. Similarly, phosphorous is oxidatively fluorinated up to the pentavalent state (Fig. 42) [107]. 

S(VI) represents the six-coordinated valence state of sulfur, which is considered to have lost its 3s and 3p electrons, making six equivalent sp3d2-hybridized orbitals available for accepting lone pairs contributed by the fluorine atoms. 

Bromine trifluoride, BrFs, is also commercially available and is used as a nonaqueous ionizing solvent. Its electrical conductivity is derived from a dissociative equilibrium (equation 82). It fluorinates most snbstrates that dissolve in it and typically gives fluorides in their highest valency state. 

When functional groups are present, the products can be quite complex. Primary and secondary amines give NF2 and NF compounds respectively and fluorination of sulphur compounds gives products in which the sulphur has been oxidised to its maximum valency state of six [149] (Table 2.4). Hydroxy compounds can give fluoroalkyl hypo-fluorites (fluoroxy compounds) (see also Chapter 3, Section IIIB), the corresponding alkyl derivatives not being stable [150, 151] bisfluoroxy derivatives have also been isolated [152-154] (Figure 2.27). 

Fluorine isHs 2p —Fluorine may be used to illustrate the main valence states of the halogens. The halogens may exist in three different valence states of which the monovalent, neutral atom /, the singly charged, negative, zerovalent ion II are well known in addition, however, there is a third possibility a singly charged, positive, divalent ion IIL... 

The adiabatic ionization energy of the anilinide anion is evaluated to be Ilia(PhNII ) = 1.7 0.1 eV, which is smaller than that of 2.25 eV measured for phenolate anion135. TD-DFT computations suggest that the lowest vertical n +- n excitations of the N-anion are centered at 1.9 eV (1 A") and 2.1 eV (l A"). Thus, its excited valence states are expected to be auto-ionizing. Substitution of the H(N) atom by fluorine increases the anion IE by 0.3 eV, whereas substitution by a methyl group slightly reduces it (0.05 eV). 

In hydrocarbons or in molecules containing atoms up to fluorine, only Is hydrogen and 2s, 2p Slater orbitals for the other elements are needed. Hu are chosen equal to valence-state ionization potentials, while Hy are given by... 

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