SULFUR(IV) COMPOUNDS AS LIGANDS, 23 - C-C COUPLING REACTIONS OF (SULFENE)RUTHENIUM COMPLEXES WITH ENOLATES

Sulfene complexes [CpRu(PR'(3))(2)(RHC=SO2)]PF6 (2a-d) are obtained fr om the corresponding sulfur dioxide complexes 1a-c and diazomethane or -ethane. Reaction of [CpRu(dppm)(SO2)]Cl (1d) and phenyldiazomethane gives the chlorobenzylsulfinato complex [CpRu(dppm)(SO2-CHPhCl)] (3). Alternatively 2a may be synthesized by sulfur dioxide addition to the carbene complex [CpRu(dppm)-(CH2)]PF6 (5) which, in turn, is obtained from the corresponding methyl complex [CpRu(dppm)(CH3)] and [Ph3C]PF6. Treatment of 2a-d or 3 with the enolates of cyclic 2-methyl-1,3-diket ones, methyl malonates, open-chain cyano or p-oxo esters, and cyclic p -oxo eaters gives the C-C coupling products 6a, b, 7a-e, 8a-c, 9a-c in high yields and, in one case, with high diastereoselectivity as well. The functionalized sulfinate Ligands thus formed may be alkylated and subsequently removed from the metal center by ligand substitution wit h acetonitrile. After MeCN/SO2 exchange, the ruthenium complex can be recycled.