Abstract The Compounds cis-[Pt(PPh3)2(4-X-C6H4)2] [X = F, Cl, CF3, OCH3, N(CH3)2] and cis-[Pt(PPh3)2(4-X-C6H4)(Y-C6H4)] [X = F/Y = 3 Cl, 4-C1, 3-CH3O, 4-CH3O; X = CF3/Y = 3-F, 4-F] have been synthesized and studied thermally with respect to the reductive elimination of disubstituted biphenyls. Activation parameters ⊿H≠ and ⊿ S≠ are reported and discussed.