Reactions of tetrachloroethylene and tetrafluoroethylene with (Ph3P)4Pt give the olefin complexes (Ph3P)2Pt(olefin). The tetrachloroethylene complex can be isomerised to the vinyl complex (Ph3P)2Pt(CClCCl2)Cl. This isomerisation is solvent-dependent. Trichloroethylene and trans-1,2-dichloroethylene with (Ph3P)4Pt give only the vinyls (Ph3P)2Pt(CHCCl2)Cl and (Ph3P)2Pt(CHCHCl)Cl, while cis-1,2-dichloroethylene and hexachloropropene give cis-(Ph3P)2PtCl2. Reactions of hexachloroethane and chloroform with Pt(PPh3)4 give cis-(Ph3P)2PtCl2, and bromotrichloromethane gives cis-(Ph3P)2PtBr2. Carbon tetrachloride gives a product which is probably (Ph3P)2Pt(CCl3)Cl. Infrared and n.m.r. spectra of the products are reported.