The coordination and transformations of a dicarboxylate substituted allence on a dimanganese carbonyl grouping

Article abstract of DOI:10.1002/cber.19961291208

Two products, Mn₂(CO)₇(PMe₂Ph)[μ-η ²-η²-MeO₂C(H)CCC-(H)CO₂Me] (1) in 9% yield arid Mn₂(CO)₆(PMe₂Ph)[μ-η ³-η¹-MeO₂CC(H)CC(H)CO₂Me] (2) in 34% yield, were obtained from the reaction of Mn₂(CO)₈(PMe₂Ph)(MeCN) with MeO₂C(H)C=C=C(H)CO₂Me. Compound 1 contains a bridging η²-η²-MeO₂C(H)CCC(H)CO₂Me allene ligand and compound 2 contains a bridging η³-η¹-MeO₂C(H)CCC(H)-CO₂Me allene ligand in which the oxygen atom of one of the carbonyl groups is also coordinated. Compound 1 slowly converts to 2, which establishes that it is a precursor to 2. Compound 2 reacts with NEtH₂ to give the mononuclear manganese complex fac-Mn(CO)₃(PMe₂Ph)[MeO₂CCH ₂-C=C(H)CO₂Me] (3) in 96% yield. Compound 3 contains a chelating 1,3-di(methoxycarbonyl)propenyl grouping formed by addition of a hydrogen atom to the aliene and the loss of a manganese grouping. Compounds 1-3 were characterized by single crystal x-ray diffraction methods. VCH Verlagsgesellschaft mbH. 1996.