Regiospecific insertion into the Co-Co bond of the mixed-metal cluster Co2Rh2(CO)12 by an electron-poor alkyne:: X-ray diffraction structure of the butterfly cluster Co2Rh2(CO)10(μ-HCCCO2Me)

The reaction between the mixed-metal tetrahedral cluster Co2Rh2(CO)(12) (1) and the electron-poor alkyne methyl propiolate in hexane at room temperature furnishes a mixture of products consisting of Co3Rh(CO)(12) (2), Co3Rh(CO)(10)(mu-HCCCO2Me) (3), Co2Rh2(Co)(10)(mu-HCCCO2Me) (4), and CoRh3(CO)(9)(mu-HCCCO2Me)(3) (5). The isolation and solution spectroscopic data of these compounds are described, and the solid-state structure of Co2Rh2(CO)(10)(mu-HCCCO2Me) determined by X-ray diffraction analysis. The title cluster crystallizes in the triclinic space group. The solid-state structure of Co2Rh2(CO)(10)(mu-HCCCO2Me) provides proof for the regiospecific insertion of the methyl propiolate ligand into the Co-Co bond of the starting cluster Co2Rh2(CO)(12). The stability of clusters 3 and 4 in the presence of added methyl propiolate is discussed. (c) 2006 Elsevier Ltd. All rights reserved.