Computational studies of transition metal catalysts

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High level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the second and third row transition metal hexafluorides, as well as for metal phosphines (M=Ni, Pd, Pt). For the 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. For the transition metal phosphines, the first metal-phosphine binding energy in MPH₃, M(PH₃)₂, MPH₃Cl₂ and M(PH₃)₂Cl₂ was calculated. The electron affinities, which are a direct measure for the oxidizer strength, increase monotonically in the second and third row series, from WF₆ to AuF₆, and from MoF₆ to AgF₆. The hexafluorides of the last two elements of each series, Pt, Au in the third row and Pd and Ag in the second, form 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, for the third row are: WF₆ (3.15 eV), ReF₆ (4.58 eV), OsF₆ (5.92 eV), IrF₆ (5.99 eV), PtF₆ (7.09 eV), and AuF₆ (8.20 eV). The electron affinities of the second row hexafluorides are even larger than for the second row: MoF₆ (4.23 eV), TcF₆ (5.89 eV), RuF₆ (7.01 eV), RhF₆ (6.80 eV), PdF₆ (7.95 eV), AgF₆ (8.89 eV). A wide range of density functional theory exchange-correlation functionals were also evaluated and only three gave satisfactory results as compared to the higher level electronic structure calculations. The corresponding pentafluorides are extremely strong Lewis acids. The optimized geometries of the corresponding MF₇⁻ anions show classical structures with M-F bonds for W through Ir and for Mo, Tc and Rh; however, for PtF₇⁻, AuF₇⁻, RuF₇⁻, PdF₇⁻, and AgF₇⁻ nonclassical anions were found with a very weak external F-F bond between an MF₆⁻ fragment and a fluorine atom. These anions are text book examples for "superhalogens" and can serve as F atom sources under very mild conditions.

Electronic Thesis or Dissertation
Physical chemistry, Inorganic chemistry