Synthesis and reactivity of dimetallacyclopentenone complexes [Ru2(CO)(μ-CO){μ-C(O)CR1CR2}(η-C5H5)2] (R1 = Me or Ph; R2 = CO2Me)

Abstract

Reactions of the dimetallacyclopentenone complex [Ru₂(CO)(μ-CO){μ-C(O)C₂Ph₂}(η-C₅H₅)₂] (1) with alkynes RCCCO₂Me (R = Me or Ph) lead to alkyne exchange, forming inseparable isomeric mixtures of [Ru₂(CO)(μ-CO){μ-C(O)C(R)C(CO₂Me)}(η-C₅H₅)₂] and [Ru₂(CO)(μ-CO){μ-C(O)C(CO₂Me)C(R)}(η-C₅H₅)₂] (2i,j, R = Ph; 2k,l, R = Me), whereas with HCCCO₂Me the μ-vinylidene complex [Ru₂(CO)₂(μ-CO){μ-CC(H)CO₂Me}(η-C₅H₅)₂] (4c) is produced. The new dimetallacyclopentenone complexes undergo fluxional processes which interconvert the isomers with free energies of activation similar to those seen previously for other diruthenacyclopentenone species. Both 2i,j and 2k,l are thermally stable but UV irradiation of 2i,j yields [Ru₂(μ-CO){μ-η²∶η²-C(Ph)C(CO₂Me)}(η-C₅H₅)₂] (5), [Ru₂(CO)₂{μ-η²∶η²-C(O)C₆H₄CC(H)CO₂Me)}(η-C₅H₅)₂] (6) and [Ru₃(CO)(μ-CO)₂{μ₃-η²-C(Ph)C(CO₂Me)}(μ-η¹∶η⁵-C₅H₄)(η-C₅H₅)₂] (7), while photolysis of 2k,l generates the μ-allylidene complex [Ru₂(CO)(μ-CO){μ-C(CO₂Me)CHCH₂}(η-C₅H₅)₂] (8). The structures of the unusual complexes 6 and 7 have been determined by X-ray diffraction studies. Complexes 5, 6 and 7 are shown to be formed from 2i,jvia independent pathways.