Metal clusters as models of intermediates in organic syntheses. Reactions of the terminal dialkynes NR(CMe2CCH)2(R = H or Me) with [Ru3(CO)12]

Abstract

The compound NMe(CMe₂CCH)₂1 reacts with [Ru₃(CO)₁₂] giving a trinuclear cluster and a dinuclear ruthenacyclopentadiene derivative. Under the same conditions, NH(CMe₂CCH)₂2 gives only the dinuclear ruthenacyclopentadiene derivative. The crystal structure of the trinuclear cluster [Ru₃(CO)₈(HC[graphic omitted]CHCCCMe₂)] has been determined by X-ray diffraction: triclinic, space group P, with a= 15.607(8), b= 15.912(7), c= 11.674(5)Å, α= 104.88(2), β= 90.01(3), γ= 103.53(2)° and Z= 4. Two independent, but practically identical, molecules are present in the crystals. In the structure a six-carbon-atom chain, formed by partial cyclization of one molecule of ligand 1 and coupling with a CCCMe₂ fragment, interacts with all three ruthenium atoms. The cluster represents a rare example of a derivative characterized by a six-carbon-atom chain co-ordinated to three metals; this interaction and its role in the synthesis of organic products is discussed.