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.