High level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the third row transition metal hexafluorides. The electron affinities, heats of formation, first (MF(6) --> MF(5) + F) and average M-F bond dissociation energies, and fluoride affinities of MF(6) (MF(6) + F(-) --> MF(7)(-)) and MF(5) (MF(5) + F(-) --> MF(6)(-)) were calculated. The electron affinities which are a direct measure for the oxidizer strength increase monotonically from WF(6) to AuF(6), with PtF(6) and AuF(6) being extremely powerful oxidizers. The inclusion of spin orbit corrections is necessary to obtain the correct qualitative order for the electron affinities. The calculated electron affinities increase with increasing atomic number, are in good agreement with the available experimental values, and are as follows: WF(6) (3.15 eV), ReF(6) (4.58 eV), OsF(6) (5.92 eV), IrF(6) (5.99 eV), PtF(6) (7.09 eV), and AuF(6) (8.20 eV). A wide range of density functional theory exchange-correlation functionals were also evaluated, and only three gave satisfactory results. The corresponding pentafluorides are extremely strong Lewis acids, with OsF(5), IrF(5), PtF(5), and AuF(5) significantly exceeding the acidity of SbF(5). The optimized geometries of the corresponding MF(7)(-) anions for W through Ir are classical MF(7)(-) anions with M-F bonds; however, for PtF(7)(-) and AuF(7)(-) non-classical anions were found with a very weak external F-F bond between an MF(6)(-) fragment and a fluorine atom. These two anions are text book examples for "superhalogens" and can serve as F atom sources under very mild conditions, explaining the ability of PtF(6) to convert NF(3) to NF(4)(+), ClF(5) to ClF(6)(+), and Xe to XeF(+) and why Bartlett failed to observe XePtF(6) as the reaction product of the PtF(6)/Xe reaction.

High-level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the second row transition metal hexafluorides. The electron affinities, heats of formation, first (MF(6) --> MF(5) + F) and average M-F bond dissociation energies, and fluoride affinities of MF(6) (MF(6) + F(-) --> MF(7)(-)) and MF(5) (MF(5) + F(-) --> MF(6)(-)) were calculated. The electron affinities are higher than those of the corresponding third row hexafluorides, making them stronger one-electron oxidizers. The calculated electron affinities, in good agreement with the available experimental values, are 4.23 eV for MoF(6), 5.89 eV for TcF(6), 7.01 eV for RuF(6), 6.80 eV for RhF(6), 7.95 eV for PdF(6), and 8.89 eV for AgF(6). The corresponding pentafluorides are also very strong Lewis acids, although their acidities on the pF(-) scale are about one unit lower than those of the third row pentafluorides. The performance of a wide range of DFT exchange-correlation functionals was benchmarked by comparing them to our more accurate CCSD(T) results.

No abstract