A comparison of unidentate and bidentate amines as entering groups in some reactions of dichloro(bipyridyl)platinum(II)

Abstract

Second-order rate constants and activation parameters have been determined for the reactions in methanol involving the replacement of one chloride from Pt(bipy)Cl₂(bipy = 2,2′-bipyridyl) by a unidentate or a bidentate amine. For the unidentate amines the values of ΔH^‡ and ΔS^‡ are 15–17 kcal mol^–1 and –12 to –17 e.u. respectively, whereas for the bidentate amines the values are 11–12 kcal mol^–1 and –27 to –28 e.u. The nature of the transition state in the reactions of the bidentate amines is discussed in terms of an ‘anchoring’ effect involving the free amine group.