METHYL PROPIOLATE COUPLING AT THE FE(CO)(2)(PET3)(2) FRAGMENT

The in situ solution mixture of Fe(CO)(2)(PEt3)(2)(N-2) 3a and (mu-N-2 )[Fe(CO)(2)(PEt3)(2)](2) 3b reacts with HC=CCOOMe to afford an acetyle ne Fe(CO)(2)(PEt3)(2)(eta(2)-HC=CCOOMe) 4a and an acetylido hydride co mplex Fe(CO)(2)(PEt3)(2)(H)(C=CCOOMe) 4b as primary products. Compound s 4a and 4b are in equilibrium. The equilibrium mixture is irreversibl y converted to a vinylidene species Fe(CO)(2)(PEt3)(2)(C=CHCOOMe) 5 in the presence of silylated silica. Addition of further equivalents of HC=CCOOMe to 5 leads to the isolation of xa-1,3,5-trien-1,5-diyl]bis(t riethylphosphane)iron 9 and 1,3-dien-2-y)vinylidene]bis(triethylphosph ane)iron 10 as iron-bound trimerization products of HC=CCOOMe. 10 was characterized by a single crystal X-ray diffraction study. (C) 1997 El sevier Science S.A.