Synthesis and Reactivity of 10- and 12-Vertex Cobalt−Monocarborane Anions Containing Multiple Metal Centers

Treatment of [closo-1-CB7H8]- with [Co2(CO)8] in THF at room temperature affords the 10-vertex dicobalt−monocarbollide anion [6,10-(μ-CO)-6,6,10,10-(CO)4-closo-6,10,1-Co2CB7H8]-, isolated as the [N(PPh3)2]+ salt (6). The analogous 12-vertex species [N(PPh3)2][2,3-(μ-CO)-2,2,3,3-(CO)4-closo-2,3,1-Co2CB9H10] (7) is obtained similarly from [arachno-6-CB9H14]- and [Co2(CO)8] heated to 50 °C. Both 6 and 7 contain a cobalt−cobalt bond that is bridged by one CO ligand. In contrast, the same cobalt reagent with [closo-4-CB8H9]- at room temperature gives the tricobalt species [6,7,10-{Co2(μ-CO)(CO)5}-7-(μ-H)-6,6-(CO)2-closo-6,1-CoCB8H7]-, similarly isolated as its [N(PPh3)2]+ salt (8a). The latter contains a V-shaped tricobalt unit, part of a {Co3B} butterfly that is edge-fused to a {CoCB8} cluster. Compounds 6 and 7 with CF3SO3Me in CH2Cl2−THF (1:1) give the zwitterionic, B-substituted complexes [6,10-(μ-CO)-6,6,10,10-(CO)4-8-{O(CH2)4}-closo-6,10,1-Co2CB7H7] (9) and [2,3-(μ-CO)-2,2,3,3-(CO)4-12-{O(CH2)4}-closo-2,...