The synthesis of [FeRu(CO)2(μ-CO)2(η-C5H5)(η-C5Me5)] and convenient entries to its organometallic chemistry

Abstract

The synthesis, fluxionality and reactivity of the heterobimetallic complex [FeRu(CO)₂(μ-CO)₂(η-C₅H₅)(η-C₅Me₅)] (5) are described. Complex 5 exhibits enhanced photolytic reactivity towards alkynes compared to its homometallic analogues, forming the dimetallacyclopentenone complexes [FeRu(CO)(μ-CO){μ-η¹:η³-C(O)CR″CR′}(η-C₅H₅)(η-C₅Me₅)] (9, R′ = R″ = H; 10, R′ = R″ = CO₂Me; 11, R′ = H, R″ = CMe₂OH). Prolonged photolysis with diphenylethyne gives the dimetallatetrahedrane complex [FeRu(μ-CO)(μ-η²:η²-CPhCPh)(η-C₅H₅)(η-C₅Me₅)] (17), which contains the first iron–ruthenium double bond. Complexes containing a number of organic fragments can be synthesised using 9, 10 and 11. Heating a solution of 10 gave the alkenylidene complex [FeRu(CO)₂(μ-CO){μ-η¹:η¹-CC(CO₂Me)₂}(η-C₅H₅)(η-C₅Me₅)] (23) through an unusual methylcarboxylate migration. Protonation and then addition of hydride to 9 gives the ethylidene complex [FeRu(CO)₂(μ-CO)(μ-CHCH₃)(η-C₅H₅)(η-C₅Me₅)] (27) via the ionic vinyl species [FeRu(CO)₂(μ-CO)(μ-η¹:η²-CHCH₂)(η-C₅H₅)(η-C₅Me₅)][BF₄] (25). Compound 25 exhibits cis/trans isomerisation at room temperature. Protonation of 11 gives the allenyl species [FeRu(CO)₂(μ-CO)(μ-η¹:η²-CHCCMe₂)(η-C₅H₅)(η-C₅Me₅)][BF₄] (30). Compound 30 exist as three isomers, two cis and one trans. The two cis isomers are shown to be interconverting by σ–π isomerisation. The solid state structures of 5, 11, 12, 17, 23, 25 and 30 were established by X-ray crystallography and are discussed.