Abstract:
The electrochemical generation and stability of nickel(1) complexes of the type [Ni(R,NCS2),(dpe)2-x]'-X ( x = 0, 1, 2; dpe = Ph2PCH2CH2PPh2) have been investigated with use of the methods of electron spin resonance (ESR) spectroscopy and cyclic voltammetry. Reduction of the bis(dithiocarbamat0) complexes Ni11(R2NCS2)2 at a Pt electrode in dichloromethane solution yields an initial planar nickel(1) species, which interconverts to a new nickel(1) species with "reversed" g values. In contrast Ni(dpe);+ undergoes two closely spaced reductions, the first of which corresponds to a nickel(1) complex with four equivalent phosphorus ligands bound to the metal. The mixed-ligand complex [Ni"(R,NCS,)(dpe)]PF, may be reduced to a nickel(1) species with two equivalent phosphorus ligands bound to the metal. This species undergoes a series of further reactions, resulting in an overall disproportionation to Ni11(R2NCS2)2 and Nio(dpe),. The kinetics and mechanism of this reaction have been investigated with use of ESR spectra and cyclic voltammetry. The nickel(1) complexes [Ni(R,NCS,),]- can also be generated by y irradiation of frozen solutions of Ni(R,NCS,),, and these have been characterized with use of ESR spectroscopy.
