Electron Affinities, Fluoride Affinities, and Heats of Formation of the Second Row Transition Metal Hexafluorides: MF₆(M = Mo, Tc, Ru, Rh, Pd, Ag)

Abstract

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.

A pseudopotential-based composite method: The relativistic pseudopotential correlation consistent composite approach for molecules containing 4d transition metals (Y–Cd)

“…The dissociation energy of 86.4 kcal mol −1 determined by rp-ccCA for MoF 6 agrees well with the value of 86.0 kcal mol −1 reported by Dixon et al 24 using CCSD(T) with ECPs. Experimental values are currently not available for this reaction.…”

“…Furthermore, Dixon et al determined the geometries, electron affinities, fluoride affinities, and enthalpies of formation for six 4d hexaflourides (Mo, Tc, Ru, Rh, Pd, Ag) with a variety of DFT methods and utilized CCSD(T) calculations with correlation consistent basis sets with corresponding effective core potentials as benchmarks. 24 The only experimental value for comparison was the enthalpy of formation of MoF 6 , for which the CCSD(T) level calculation was within 2 kcal mol −1 . Fluoride affinities, electron affinities, and bond dissociation energies (BDEs) calculated via DFT had deviations from the CCSD(T) results ranging from 5 kcal mol −1 to 28 kcal mol −1 .…”

“…While the hybrid functionals yielded the best performance, the average deviations were still 5-6 kcal mol −1 . 24 Another study by Dixon et al determined thermochemical properties, including total atomization energies (TAEs) and enthalpies of formation, for transition metal oxide clusters via CCSD(T) and DFT methods. The DFT results were found to degrade with increasing cluster size and performance was strongly dependent on the electronic state of the transition metal atom.…”

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…[305] Overall, the oxidation potentials of the third-row hexafluorides increase from WF 6 to PtF 6 ,w ith the latter being ap articularly potent oxidant with ac alculated oxidation potential of 7.09 eV. [305,307] Thec lear trend in oxidation potentials outlined above means transition-metal hexafluorides represent at unable oxidant through choice of the metal. [305,307] Thec lear trend in oxidation potentials outlined above means transition-metal hexafluorides represent at unable oxidant through choice of the metal.…”

Structure and properties of the aluminum borates Al(BO2)n and Al(BO2)n−, (n = 1–4)

“…For smaller Al(BO 2 ) n species, we used the hybrid DFT methods: B3LYP, [45] where the exchange-correlation functional is composed of the Becke's hybrid three-parameter exchange functional and Lee-Yang-Parr's correlation functional, [46] B3PW91, where the Becke's hybrid three-parameter exchange is combined with the Perdew-Wang correlation, [47] and M06 [48] ; the DFT methods: TPSSTPSS with the s-dependent gradient-corrected functional [49] ; PBEPBE, [50] PW91PW91, [51] and BPW91 [47,52] with generalized gradient approximations for the exchange-correlation functional. The choice of a proper method is critical in obtaining reliable results, [53][54][55][56] and can be based on comparison of the results obtained using a particular method to experiment or to the results obtained [57,58] using a high-quality method such as CCSD(T). [59] Our single-point CCSD(T) calculations were performed using the geometrical configurations optimized using the second-order perturbation theory method (MP2).…”