Dinuclear Cp*Co Amido and Alkoxo Complexes: Synthesis, Structures, and Reactivity

New amido- and alkoxo-bridged dinuclear cobalt complexes [Cp*Co(μ-X)]2 (X = NHTol (2), NHBoc (3), OBn (4); Cp* = η5-C5Me5; Tol = p-tolyl; Boc = t-BuOCO; Bn = CH2Ph) have been prepared by the reaction of [Cp*Co(μ-Cl)]2 (1) with LiX and characterized by X-ray analysis. The amido complexes 2 and 3 are diamagnetic and feature a folded Co2N2 butterfly structure with a Co−Co single bond. In contrast, the alkoxo complex 4 is paramagnetic and contains a planar Co2O2 core with a long Co···Co separation. Dynamic stereochemical processes in 2 and 3 were investigated by NMR spectroscopy, and cis−trans isomerization in 2 and Co2N2 ring inversion in 2 and 3 were identified. Complexes 2 and 4 reacted with carbon monoxide to give N,N′-di-p-tolylurea and dibenzyl carbonate, respectively, along with [Cp*Co(CO)2] and [Cp*Co(μ-CO)]2. Oxidation of 2 with iodine and ferrocenium triflate afforded the Co(III) complexes [(Cp*Co)2(μ-I)(μ-NHTol)2]I (5) and [(Cp*Co)2(μ-OH2)(μ-NHTol)2][OTf]2 (6), respectively, the latter being characterized by X-ray analysis.