Mechanism of the Formation of Platina-β-diketones: A DFT Study

Abstract

Based on experimental findings that formation of dinuclear platina-β-diketones [Pt2(μ-Cl2{(COR)2H}2] from reactions of hexachloroplatinic acid with silylated alkynes R‘C⋮CSiMe3 (R = CH2R‘) proceeds most likely via terminal alkyne complexes of Zeise's salt type [PtCl3(η2-R‘C⋮CH)]-, DFT calculations using the hybrid functional B3LYP of reaction mechanism were performed. Reaction of propyne complex [PtCl3(η2-MeC⋮CH)]-, 10, with MeC⋮CH and OH-/H2O affording mononuclear platina-β-diketonate anion [PtCl2{(COEt)2H}]-, 11, was used as a model. Formation of complex 11 from complex 10 proved to be strongly exothermic (ΔE = −176.8 kcal/mol). Four reaction types were taken into consideration: (a) equilibration (tautomerization) between alkyne and vinylidene complexes, (b) substitution of a chloro ligand by an alkyne, (c) addition of water to a vinylidene ligand affording a hydroxycarbene ligand, and (d) deprotonation of a hydroxycarbene ligand affording an acyl ligand. Results show that the reaction proceeds as foll...