Copper(II)-promoted solvolyses of nickel(II) complexes. I. N,N-Dialkyldithiocarbamates

Abstract

The kinetics of copper(II)-promoted solvolyses of bis(N,N- dibutyldithiocarbamato)nickel(II) in dimethyl sulphoxide (dmso), N,N- dimethylacetamide (dma), acetone, and chloroform, and bis(N,N- dicyclohexyldithiocarbamato)nickel(II) in dmso and dma have been examined. Although the reaction stoichiometry differs in chloroform compared with the other solvents, in all media the two-term rate law                   -d[Ni(dtc)₂]/dt = (k₁+k₂[Cu²⁺])[Ni(dtc)₂] is obeyed. However, in the absence of added sodium and nickel ions, experiments in dmso at low [Cu²⁺]_O, indicate a negligible contribution from the k₁ path. Results are discussed in the light of a mechanism involving primary dissociative (k₁) and associative (k₂) steps. Although the ratios k2/k₁ indicate overall importance for the associative pathways of reaction in the low dielectric media cf. dmso and dma, the k₁ term also appears as a significant contributor to the reaction of the dibutyldithiocarbamate complex in the former solvents.