Synthesis of conjugated diene complexes of ruthenium(0) derived from Ru(畏up>6up>-naphthalene)(畏up>4up>-1,5-COD): Z to E isomerisation of coordinated 1,3-pentadiene
摘要
The naphthalene complex of zerovalent ruthenium, [Ru(畏up>6up>-Cub>10ub>Hub>8ub>)(畏up>4up>-1,5-COD)] (1), readily reacts with 1,3-dienes in the presence of a ligand (L) to produce complexes [Ru(畏up>4up>-cisoid-1,3-diene)(畏up>4up>-1,5-COD)(L)] [1,3-diene聽=聽butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-cyclohexadiene; L聽=聽MeCN, up>tup>BuCN, PhCN, NCCub>6ub>Hub>4ub>CN, CO, up>tup>BuNC, pyridine, P(OMe)ub>3ub>, P(OPh)ub>3ub>, PMeub>3ub>, PEtub>3ub>, PPhub>3ub>, PCyub>3ub>]. The single-crystal X-ray structures of [Ru(畏up>4up>-cisoid-1,3-butadiene)(畏up>4up>-1,5-COD)(MeCN)] (2a) and [Ru{畏up>4up>-(E)-cisoid-1.3-pentadiene}(畏up>4up>-1,5-COD)(PPhub>3ub>)}] (E-5l) show the expected, approximately square pyramidal geometry about the metal atom, with the auxiliary ligand occupying the axial site. [Ru{畏up>4up>-(Z)-cisoid-1,3-pentadiene}(畏up>4up>-1,5-COD)(PPhub>3ub>)] (Z-5l) irreversibly isomerises to E-5l in benzene-dub>6ub> at 30聽掳C, the reaction obeying a first-order rate law [k聽= (2.89聽卤聽0.06)聽脳聽10up>鈭?up>聽sup>鈭?up>]. This reaction is significantly retarded by addition of PPhub>3ub> suggesting that a vacant site is required for the E/Z isomerisation.