REDOX PROPERTIES OF THE NICKEL(II),(I),(O)-TRIPHENYLPHOSPHINE SYSTEM IN ACETONITRILE

The cathodic behaviour of electrochemically generated nickel(II) has been investigated in acetonitrile in the presence of triphenylphosphine at a platinum electrode. An appropriate combination of voltammetric, spectrophotometric and NMR findings has allowed us to establish that Ni(II) is present in solution as [Ni(PPh3)2 (CH3CN)42+.]. For the reduction of this species an EECE mechanism is proposed which is consistent with the data. It undergoes an irreversible two-electron reduction giging the Ni(0) complex [Ni(PPh3)4] which reacts quickly with the depolarizer. In this last homogeneous redox reaction the not previously reported Ni(I) complex [Ni(PPh3)4+] is obtained. The degree of reversibility of the redox processes involved has been discussed taking into account the structure, the coordination number and the nature of the ligands in both the redox partners. © 1979 Elsevier Sequoia S.A.