Nuclear magnetic resonance spectra and structure of some trimethylplatinum(IV) compounds

Abstract

The nuclear magnetic resonance spectra of twenty-three trimethylplatinum(IV) compounds are presented and discussed in terms of the structure of the molecules in solution. It is shown that the spin–spin coupling constant between the ¹⁹⁵Pt nucleus and the methyl protons is sensitive to the chemical nature of the ligand trans to it in the complex, thereby providing a sensitive indication of the stereochemistry and chemical equivalence of the bonds to the platinum atom. Salts of trimethylplatinum(IV) are shown to ionise extensively in solution to give {PtMe₃(OH₂)₃}³⁺; in the salicylaldehyde dimer, {PtMe₃(sal)}₂, the four Pt–O bridge bonds appear to be equivalent, whereas in the 8-hydroxyquinoline dimer, {PtMe₃(oxine)}₂, the same criteria require non-equivalence. Coupling from ¹⁹⁵Pt to protons attached to the β-diketone ligand has been observed in several complexes of the type PtMe₃(acac)(quin) and {PtMe₃(acac)}₂; in the latter, the results are consistent with some dissociation of the complex provided that the Pt–O rather than the Pt–CH bonds are broken.