Kinetics and mechanisms of the ligand substitution reactions of bis(amine)(cyclobutane-1,1-dicarboxylato)palladium(II)†

Abstract

Kinetic and mechanistic investigations have been made on the displacement of the bidentate cyclobutane-1,1-dicarboxylate ligand (cbdca) from the complexes [Pd(en)(cbdca)] (en = ethane-1,2-diamine) and [Pd(bpy)(cbdca)] (bpy = 2,2′-bipyridine). Two consecutive reaction steps were observed for the substitution of cbdca with thiourea (tu), tetramethylthiourea (tmtu), inosine 5′-monophosphate (5′-IMP) and iodide, as well as for the acid-catalysed hydrolysis reaction. After displacement of cbdca by tu and tmtu the strong trans influence of the Pd-bound sulfur-containing nucleophiles resulted in displacement of the en ligand from [Pd(en)(cbdca)], whereas no such reaction was found to occur for [Pd(bpy)(cbdca)]. All rate and activation parameters are consistent with associative substitution mechanisms.