Oxidative addition - reductive elimination sequences in the photochemistry of some bis(phosphine)platinum complexes

The photolysis of [L2Pt(C2H4)] (L = PPh3, P(p-C6H4CH3)3 complexes in halocarbon solvents (CH2Cl2, CH2Br2) gives C2H4 and the coordinatively unsaturated species [L2Pt]. Photolysis of platinum metallacycles [L2Pt(CH2)4] (L = PPh3, P(n-Bu)3) generates alkanes, alkenes and [L2Pt]. The [L2Pt] centers are very reactive, and under prolonged photolysis undergo oxidative addition of CH2Cl2 forming the trans-[L2Pt(CH2Cl)Cl] complexes. Under appropriately controlled conditions the trans complexes isomerize to cis species before bimolecular C2H4 elimination occurs and [L2PtCl2] is formed as the final product. The oxidative addition-reductive elimination mechanism is discussed on the basis of spin-trapping experiments, quantum yield values, and the sensitivity to radical inhibitors and to solvents. © 1983.