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(μ-HCCCO2Me) (3), Co2Rh2(CO)10(μ-HCCCO2Me) (4), and CoRh3(CO)9(μ-HCCCO2Me)3 (5). The isolation and solution spectroscopic data of these compounds are described, and the solid-state structure of Co2Rh2(CO)10(μ-HCCCO2Me) determined by X-ray diffraction analysis. The title cluster crystallizes in the triclinic space group. The solid-state structure of Co2Rh2(CO)10(μ-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.

Graphical abstractTreatment of the mixed-metal cluster Co2Rh2(CO)12 with the electron-poor alkyne methyl propiolate in hexane at room temperature gives a mixture of products that includes Co3Rh(CO)12, Co2Rh2(CO)10(μ-HCCCO2Me), Co3Rh(CO)10(μ-HCCCO2Me), and CoRh3(CO)9(μ-HCCCO2Me)3. The alkyne-substituted products have been characterized in solution by IR and 1H NMR spectroscopies, and X-ray diffraction analysis in the case of Co2Rh2(CO)10(μ-HCCCO2Me). The observed chemistry is discussed relative to the results reported for the reaction of Co2Rh2(CO)12 with other alkyne ligands.Figure optionsDownload full-size imageDownload as PowerPoint slide