The preparation of trimethylsilyl and trimethylgermyl complexes of platinum(II) of the type trans-(Et3P)2Pt(MMe3)Cl (M = Si and Ge) from (Me3M)2Hg and cis-(Et3P)2PtCl2 is described. Several reactions are reported involving both chloride ion replacement (Br–, I–, CN–, NCS–, Ph–, and GePh3–) and cleavage of the Pt–M bond [H2O, PhC⋮CH, (CH2Cl)2, and H2]. The hydrogenation at 1 atmosphere has been studied in some detail, and both the Me3Ge and the Me3Si groups are cleaved in preference to the Ph3Ge group in the complexes trans-(Et3P)2Pt(MMe3)(GePh3) Infrared and 1H n.m.r. spectroscopy have been used to determine the stereochemistry of these complexes. Platinum–silicon, –phosphorus, and –chlorine stretching frequencies have been assigned. In cis-complexes, e.g., (Et3P)2PtPh(GeMe3), a unique long-range coupling between the Me3Ge protons and the trans-31P nucleus is observed. The mass spectrum of trans-(Et3P)2Pt(GeMe3)Cl is described.