The interactions of various substances which can undergo oxidative addition reactions with complexes of rhodium, iridium, and platinum have been studied and the new compounds characterised by i.r. and n.m.r. spectroscopy. The reactions investigated are the following : (a) CS2 with RhX(PPh3)3(X = Me or Ph), RhH(CO)(PPh3)3, RhHCl2(PEtPh2)3, Rhl2Me(PPh3)2, IrH(CO)(PPh3)2; (b) CICSSEt with trans-RhCl(CO)-(PPh3)2, trans-RhCl(CO)[P(C6H4OMe)3]2, RhCl(PPh3)3, trans-IrCl(CO)(PPh3)2, and Pt(PPh3)3; (c)(CF3)2CS with IrH(CO)(PPh3)3; (d) C6H4(NH2)SH with RhCl(PPh3)3, trans-RhCl(CO)(PPh3)2,Rh(CO)2(acac), and [Rh(CO)2Cl]2; (e) Ph2PSSH with RhCl(PPh3)3; and (f) RCO2H with RhCl(PPh3)3 and IrH(CO)(PPh3)3.