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 (MF6 -> MF5 + F) and average M-F bond dissociation energies, and fluoride affinities of MF6 (MF6 + F- -> MF7-) and MF5 (MF5 + F- -> MF6-) 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 MoF6, 5.89 eV for TcF6, 7.01 eV for RuF6, 6.80 eV for RhF6, 7.95 eV for PdF6, and 8.89 eV for AgF6. 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.