Synthesis, structure, and reactivities of the Ru-Co heterobimetallic complex.: Molecular structures of Cp*Ru(CO)2(μ2-CO)Co(CO)3, Cp*Ru(μ2-CO)2(μ2-dppm)Co(CO)2, Cp*Ru(CNBut)(CO)(μ2-CO)Co(CO)3, and Cp*(CO)Ru{η2:η4-μ2-C(Tol)CHC(Tol)CH}Co(CO)2 (Cp* = η5-C5Me5, dppm = Ph2PCH2PPh2, Tol = C6H4Me-4)

Treatment of Cp*Ru(CO)(2)Cl (Cp* = eta(5)-C5Me5) with NaCo(CO)(4) produces the metal-metal bonded heterobimetallic complex Cp*Ru(CO)(2)(mu(2)-CO)Co(CO)(3) (2b). Substitution of the CO ligands by the Ph2PCH2PPh2 (dppm) leads to the isolation of Cp*Ru(mu(2)-CO)(2)(mu(2)-dppm)Co(CO)(2) (3) whereas that by (BuNC)-N-t gives Cp*Ru(CO)(CNBut)(mu(2)-CO)Co(CO)(3) (4). Stoichiometric head-to-tail dimerization of p-tolylacetylene at the bimetallic site of 2b proceeds to form the dinuclear metallacyclopentadiene complex Cp*(CO)Ru{eta(2):eta(4)-mu(2)-C(Tol)CHC(Tol)CH}Co(CO)(2) (5) in which two alkyne molecules are coupled to form a ruthenacyclopentadiene core which coordinates to the Co(CO), fragment. On the other hand, catalytic head-to-head coupling of methyl propiolate in the presence of 2b yields (E)-(MeO2C)CH=CH(C=CCO2Me) (6). The molecular structures of 2b, 3, 4, and 5 have been determined by X-ray crystallography. (C) 2000 Elsevier Science S.A. All rights reserved.