Metal Complexes in Acetic Acid. I. Kinetics and Mechanism of Reactions of Tetra-μ-acetato-dicopper(II) with Lithium Chloride and Hydrogen Chloride

Kinetics of reactions of tetra-μ-acetato-dicopper(II) (copper(II) acetate dimer: Cu2(OAc)4) with lithium chloride and hydrogen chloride (XCl where X denotes Li or H) in acetic acid have been studied spectrophotometrically by using a stopped-flow technique with a computer-assisted averaging device. The rate of decomposition of copper(II) acetate dimer to the monomeric chloro complex is expressed as −d[Cu2(OAc)4]/dt=kXCl[Cu2(OAc)4][XCl]. At 25 °C kLiCl=(3.5±0.6)×105 mol−1 kg s−1 (ΔH=50±10 kJ mol−1 and ΔS=30±20 J mol−1 K−1) and kHCl=(4.8±1.0)×105 mol−1 kg s−1 (ΔH=23±10 kJ mol−1 and ΔS=−60±20 J mol−1 K−1). Mechanisms are proposed for the decomposition of copper(II) acetate dimer and some discussions are made on the difference in reactivities of LiCl and HCl.