Reactions of cyclopentadiene with carbonyl-ruthenium and -osmium complexes

Abstract

Both Ru₃(CO)₁₂ and [H₄Ru₄(CO)₁₂] react rapidly with cyclopentadiene in the absence of oxygen to yield [RuH(CO)₂(η-C₅H₅)], (II; M = Ru), quantitatively, characterised in part via high-yield conversion into [RuH(CO)(PPh₃)(η-C₅H₅)]. In the presence of oxygen [{Ru(CO)₂(η-C₅H₅)}₂], (III; M = Ru), is obtained in ca. 70% yield. The complex [Ru(CO)₃(η-C₅H₆)], (I; M = Ru), has been isolated and shown to be a direct precursor of (II). Treatment of (I; M = Ru) with [Ph₃C][BF₄] gives [Ru(CO)₃(η-C₅H₅)][BF₄], while triphenyl-phosphine displaces C₅H₆ forming [Ru(CO)₃(PPh₃)₂]. Carbonylation (100 atm) of [RuH(CO)(PPh₃)(η-C₅H₅)] in the presence of Et₂O·BF₃ gives [Ru(CO)₂(PPh₃)(η-C₅H₅)][BF₄] in high yield. A minor product of the reaction of Ru₃(CO)₁₂ and C₅H₆ is tentatively identified as [Ru₃H(CO)₉(η³-C₅H₅)], (IV); a related fluxional osmium complex, [Os₃H₂(CO)₉(η²-C₅H₄)], is obtained on treating [H₂Os₃(CO)₁₀] with C₅H₆. Low-yield formation of (I; M = Os) and (II; M = Os) from reaction of Os₃(CO)₁₂, [H₂Os₃(CO)₁₀], or [H₂Os(CO)₄] with C₅H₆ is described.