Transition-metal complexes with sulfur ligands. 94. Synthesis and reactivity of nickel, palladium, and platinum complexes with the thiolate carbene ligand 'S2C'2-. X-ray structure determinations of Ni(PMe3)('S2C'), Ni(PPh3)('S2C'), Ni('SC')2, Pt(PMe3)('S2C'), and ('S2CO')2