Bond energies and thermal decomposition of {Pt(X)(CH3)[P(C2H5)3]2} complexes.

The thermal decomposition of the complexes trans-[Pt(X)(CH3)L2] (L  P(C2H5)3; X  Cl, Br, I, CN) in decalin at 170 and 200°C affords methane platinum metal and [Pt(X)2L2]. The kinetics of the decomposition of the complexes were determined by monitoring the appearance of methane by GLC. The observed first-order rate constant was found to be independent on the nature of the ligand X. The thermal decomposition of the trideuteriomethyl complexes [Pt(X)(CD3)L2] (X  I, CN) in decalin-d18 at 170 and 200°C was studied by GLC/MS. The thermolysis affords CD3H and CD4 in ratios which are independent of the nature of X and of the temperature used. The mass spectra of the complexes were also examined. A relative scale of platinum-to-methyl bond dissociation energies has been established by measuring the appearance potential of the fragment ion [Pt(X)L2]+ and the ionization energies in the series [Pt(X)(CH3)L2]. Ionization potentials and PtCH3 bond energies show a clear dependence on the nature of X which is not reflected in corresponding changes in the decomposition rates.