Selective Activation of CH Bonds in Polar Vinyl Olefins and Coupling of Ethylene to the Activated Carbon Atoms in Pentaruthenium Complexes.

Ru(μ-C)(CO), 1, has been found to activate CH bonds in the vinyl group of polar vinyl olefins, methyl acrylate (MA), and vinyl acetate (VAc), through a cluster opening process to yield the complexes Ru(μ-C)(CO)η-O═C(OMe)CH═CH, 2, and Ru(μ-C)(CO)η-(MeCO)C═CH, 4, respectively. The site of CH activation is dependent on the olefin substituent. In 2, the site of CH activation is the β-carbon atom of the vinyl group, while in 4 the CH activation has occurred exclusively at the α-carbon atom of the vinyl group. Compound 2 can be further decarbonylated to yield the complex Ru(μ-C)(CO)μ-η-O═C(OMe)CHCH, 3, which contains a η-bridging acryloyl ligand. Compound 2 reacts with ethylene in the presence of MeNO to yield three new Ru products: Ru(μ-C)(CO)η-1- anti,3- syn-{O═C(OMe)}C(H)C(H)C(H)Me, 5, Ru(μ-C)(CO)(CH)μ-η- O═C(OMe)C(H)C(H), 6, and Ru(μ-C)(CO)η- anti-O═C(OMe)HCHCHCH, 7. Compounds 5 and 7 are isomers containing substituted η-allyl ligands formed by the coupling of the ethylene to the CH-activated β-carbon atom of the acryloyl ligand accompanied by some metal-mediated H-shifts. Compound 6 contains an uncoupled π-coordinated ethylene ligand. Compound 7 was isomerized to 5 thermally at 80 °C. Compound 4 reacts with ethylene in the presence of MeNO to yield two new Ru products: Ru(μ-C)(CO)[η-1,1- anti- syn-(OCMe)C(Me)CHCH, 8, and Ru(μ-C)(CO)η-1- anti-CH(Me)C(OCMe)(CH), 9. Compounds 8 and 9 both contain substituted η-allyl ligands formed by the coupling of the ethylene to the CH-activated α-carbon atom of the vinyl acetyl ligand. Compound 8 was isomerized to 9 thermally at 80 °C. All new products were characterized structurally by single-crystal X-ray diffraction analyses.