Synthesis, structure, and reactivity of novel ruthenium(II) phenolate complexes

Reaction of Ru(eta(6)-cot)(dmfm)(2) (1) [cot = 1,3,5-cyclooctatriene, dmfm = dimethyl fumarate] with phenol was investigated. At 110degreesC, a novel ruthenium(II) phenolate complex, Ru(eta(5)-C6H5O)(eta(5)-C8H11) (2), was obtained by the reaction of 1 with phenol in an isolated yield of 52% (74% by NMR). When the reaction was carried out at 130degreesC, further dehydrogenative ring-closure in an eta(5)-cyclooctadienyl ligand occurred to give Ru(eta(5)-C6H5O)(eta(5)-C8H9) (3) in an isolated yield of 61% (76% by NMR). For both complexes, the eta(5)-oxocyclohexadienyl bonding mode of a phenoxo ligand was clearly shown by X-ray crystallography and DFT calculation. Complex 2 was smoothly transformed into complex 3 in the presence of dmfm at 130degreesC for 3 h. Selective O-methylation of an eta(5)-oxocyclohexadienyl ligand in complex 3 proceeded with methyl p-toluenesulfonate to give a novel cationic ruthenium(II) complex, [Ru(eta(6)-C6H5OMe)(eta(5)-C8H9)]+OTs- (4), in an isolated yield of 74%.