Reactions of the cyclopentadienyl ruthenium complexes (C_5R _5)Ru(cod)Cl and [(C_5R_5)Ru(MeCN) _3]~+ (R = H, Me) with phenylacetylene and acetic acid: Unexpected difference in reactivity of CpRu and Cp*Ru complexes

摘要

Reaction of CpRu(cod)Cl with phenylacetylene and AcOH gives an unusual binuclear ruthenium complex CpRu(μ-σ,η~3: η~3,σ-C_6H_3Ph_3)RuCp (5, 58% yield) with a bridging acyclic flyover ligand C_6H_3Ph _3. Under similar conditions [CpRu(MeCN)_3]~+ undergoes an unexpected cleavage of Cp ligand giving 4,7-diphenyl-3a,7a- dihydroindene (6, 65% yield). In sharp contrast, the pentamethylated congeners Cp*Ru(cod)Cl and [Cp*Ru(MeCN)_3]~+ react with phenylacetylene and AcOH in catalytic fashion giving 1,4-diphenyl-1-acetoxy-1,3- butadiene. The structures of 5 and 6 were established by X-ray diffraction. The mechanism of Cp ligand cleavage was proposed on the basis of DFT calculations.