Reaction of ethylene with [Ru3(CO)12] and the dynamic processes of [Ru3H2(CO)9(C2R2)](R = H, Me, and Et)

Abstract

[Ru(CO)₄(H₂CCH₂)] is rapidly formed during the reaction of [Ru₃(CO)₁₂] with ethylene. However, prolonged reflux yielded a mixture of products of which [Ru₃H₂(CO)₉(C₂R₂)][(1), R = H; (2), R = Me; (3), R = Et], [Ru₃H(CO)₉(RCCHCEt)][(4), R = Me; (5), R = Et], and [Ru₄(CO)₁₂(MeCCMe)](6) have been identified. Complexes (1), (2), and (3) are all stereochemically non-rigid. Generation of an apparent symmetry plane by a hydride migration is observed for all three complexes (mechanism 1). The hydride sites are equivalenced in (2) and (3), and the hexyne complex (3) was found to undergo hydride site exchange (mechanism 2) and alkyne oscillation (mechanism 3), probably independently. Increasing the acetylene alkyl group size also increases the rates of the exchange processes.