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.