Abstract 1H NMR spectra of complexes of the types Pt(CH 3) 3L 2X (L 2 = 2,2′-bipyridine, bis(pyridine), or bis(3,5-lutidine), and X = uninegative unidentate ligand); [Pt(CH 3) 3BipyX]ClO 4 (X = neutral unidentate ligand), and Pt(CH 3) 3LI (L = substituted 2,2′-pipyridine or 1,10-phenanthroline) have been recorded. The magnitude of J( 195PtCH) for the methyl group trans to X has been found to be markedly dependent on X, with values ranging from 40.5 to 82.0 Hz. Much smaller variations occur in J( 195PtCH) for the methyl groups trans to the heterocyclic ligands as X is varied (< 6 Hz), or for the methyl trans to I as the heterocyclic ligand is varied (< 5 Hz). The order of trans influence for a series of ligands X has been found to be CH 3 > CN > PPh 3 > NO 2 > amines ∼ Py ∼ SCN > NCO ∼ NCS ∼ I > Br ∼ Cl >/ CH 3COO > NO 3 > H 2O. Infrared data for the vibrations of X, where X = polyatomic uninegative ligand, and for the methyl vibrations have also been recorded.