The complexes cis-[Pt(C2H4)Cl2L](L = triorganophosphine) react with compounds SnRMe, (R = aryl)(1 mol equivalent) to give the chloride-bridged arylplatinum complexes [Pt2R2Cl2L2], which exist in solution as mixtures of cis and trans isomers. The [Pt2R2Cl2L2] complexes react with ligand species L′[L′= NCMe, SBut2, pyridine, NBunH2, AsPh3, PEt3, PBun3, PPh3, or P(OPh)3] to give the mononuclear complexes [PtR(Cl)L(L′)], and this represents an excellent route to mononuclear complexes having four different ligands on platinum. Cyclo-octa 1,5-diene (cod), however, gives [PtR(Cl)L2] and [Pt(cod)R(Cl)], while 2,2′-bipyridyl (bipy) gives the salt [PtR(bipy)L]Cl. Sodium thiocyanate reacts with [Pt2(C6H4Me-p)2Cl2(PEt2Ph)2] to give the thiocyanate-bridged [Pt2(C6H4Me-p)2(PEt2Ph)2(µ-SCN)2], and [NEt4]Cl reacts with [Pt2(C6H4Bun-p)2(PMe2Ph)2] to give the salt [NEt4][Pt(C6H4Bun-p)Cl2(PMe2Ph)]. Excess of SnRMe3 causes decomposition of [Pt2R2Cl2L2] to give the mononuclear complexes [PtR(Cl)L2]. The carbonyl complexes cis-[Pt(CO)Cl2L] react with SnRMe3 to give the binuclear aroyl complexes [Pt2(COR)2Cl2L2], which also exist in solution as mixtures of cis and trans isomers. These complexes react with neutral ligand species L′= NBunH2 or P(OPh)3 to give the mononuclear complexes [Pt(COR)Cl(L)L′]. but cod reacts with [Pt2(COC6H4But-p)2Cl2(PMe2Ph)2] to give [Pt(COC6H6But-p)Cl-(PMe2Ph)2]. Again excess of SnRMe3 causes decomposition, to give [Pt(COR)Cl(L)] complexes. Heating of the aroyl complex [Pt2(COC6H4Me-p)2Cl2(PEt3)2] gives some of the corresponding aryl complex [Pt2(C6H4Me-p)2-Cl2(PEt3)2]. The 31P-{1H} n.m.r. spectra of the complexes have been recorded, and are used extensively in the identification of products.