Element-Element Bond Formation upon Oxidation and Reduction.

The redox chemistry of [(Cp'''Co) (μ,η :η -E ) ] (E=P (1), As (2); Cp'''=1,2,4-tri(tert-butyl)cyclopentadienyl) was investigated. Both compounds can be oxidized and reduced twice. That way, the monocations [(Cp'''Co) (μ,η :η -E )][X] (E=P, X=BF (3 a), [FAl] (3 b); E=As, X=BF (4 a), [FAl] (4 b)), the dications [(Cp'''Co) (μ,η :η -E )][TEF] (E=P (5), As (6)), and the monoanions [K(18-c-6)(dme) ][(Cp'''Co) (μ,η :η -E )] (E=P (7), As (8)) were isolated. Further reduction of 7 leads to the dianionic complex [K(18-c-6)(dme) ][K(18-c-6)][(Cp'''Co) (μ,η :η -P )] (9), in which the cyclo-P ligand has rearranged to a chain-like P ligand. Further reduction of 8 can be achieved with an excess of potassium under the formation of [K(dme) ][(Cp'''Co) (μ,η :η -As )] (10) and the elimination of an As unit. Compound 10 represents the first example of an allylic As ligand incorporated into a triple-decker complex.