The kinetics and mechanism of the reaction between nickel(II) and dithiocarbamate ions in dimethyl sulfoxide. Evidence for the ID mechanism for a bidentate uninegative ligand

Abstract

¹³C Fourier-transform N.M.R. has been used to measure the rate of exchange of dimethyl sulfoxide with hexakis(dimethyl sulfoxide)nickel(II) cation. The parameters obtained, k_ex(25°C)(9.8±4.6) × 10³ s^-1, ΔH^‡ 50±2 kJ mol^-1 and ΔS^‡ 0±4 J K^-1 mol^-1, are in excellent agreement with those of the most recent ¹H N.M.R. study. The reaction between Ni(Me₂SO)₆²⁺ and diethyldithiocarbamate (dtc-) gives only Ni(dtc)₂. When dtc- is in excess, the rate of formation of Ni(dtc)₂ is first order in Ni²⁺ and dtc^-. The ionic-strength and temperature dependences of the second-order rate constants are consistent with the rate-determining formation of an unstable Ni(dtc)⁺ complex by an I_D mechanism.