ELECTROCHEMICAL-BEHAVIOR OF BIS(CYCLOPENTADIENYLNICKEL)-ALKYNE DERIVATIVES

The electrochemical behavior of dimetallic [Ni(2)Cp(2)](RC=CR') (Cp = pi-cyclopentadienyl; R = R' = Ph; COOMe; R = H, R' = Ph; R = Me, R' = Ph; R = Ph, R' = -C=CPh) and tetrametallic M(2)M(2)'(PhC=CC=CPh) (M(2) = M(2)' = Ni(2)Cp(2); M(2) = Ni(2)Cp(2), M(2)' = Co-2(CO)(6)) derivat ives has been investigated. All dinickel compounds undergo an electroc hemically and chemically reversible le (metal-centered) reduction foll owed by further ligand-based reductions. The tetrametallic complex [Ni (2)Cp(2)](2)(PhC=CC=CPh) shows two fully reversible le (metal-centered ) reductions, indicating a strong electronic communication between the two redox units (Delta E(o) = 670 mV). The mixed-metal [Ni(2)Cp(2)][C o-2(CO)(6)](PhC=CC=CPh) derivative exhibits a 1e (Co-2-centered) reduc tion at first, followed by a further 1e (Ni-2-centered) reduction; suc h an electrochemical scenario is complicated by a fast decomposition f ollowing the first reduction, which produces some amount of [Ni(2)Cp(2 )](PhC=CC=CPh) compound, having a dangling (uncoordinated) triple bond .