Reductive degradation of tetracobalt cluster complexes with a facial C8H8 ligand -: Synthesis of [Co3(CO)3(μ3-CO)3(μ3-C8H8)]- and [Ru(C5Me5)Co3(CO)3(μ3-CO)3(μ3-C8H8)]

Chemical reduction of the cluster complexes [Co-4(CO)(3)(mu(3)- CO)(3)(mu(3)-C8H8)L-2] 3 (L-2 = C8H8), 4 (L = CO), 5 (L-2 = C6H8) and 6 (L-2 = 6,6-Ph2C6H4) gives the trinuclear anion [Co-3(CO)(3)(mu(2)-CO)(3)(mu(3)-C8H8)](-) (7) in high yield. It is proposed that formation of 7 occurs via degradation of the radical anions [3]- [6]-, which can be generated reversibly via cyclic voltammetry. The anion 7 is stabilised by the facial C8H8 ligand and does not degrade further. Reaction of 7 with [(C5Me5)Ru(NCMe)(3)][BF4] results in the formation of [Ru(C5Me5)Co-3(CO)(3)(mu(3)-CO)(3)(mu(3)-C8H8)] (8). The crystal structures of [NEt4](+)-7, [(C5H5)(2)Co](+)-7, and 8 were determined. In 7 and 8, the cyclooctatetraene ligand is coordinated to the Co-3 face of the cluster in the facial mode.