Mr. Tam King Ting
Osmafuran complexes in the form of cis-[Os(L^L)2(C^O)]+ (L^L = 1,1-bis(diphenylphosphino)methane (dppm) or 2,2’-bipyridine (bpy); C^O = [C(CH3)C(CH3)CRO]−, coordinating atoms in italics) were prepared from reactions between dichloro-Os(II) complexes cis-[Os(L^L)2Cl2] and allenols H2C=C=C(CH3)(CH(R)(OH)) in alcoholic solvents. Rearrangement of allenolates H2C=C=C(CH3)(CH(R)(O−)) involving deprotonation of the secondary alcoholic carbon and protonation of the terminal allenic carbon was evident from the X-ray crystal structures of the resulting complexes. Density functional theory (DFT) calculations suggested a rearrangement mechanism involving Os-alkene intermediates cis-[Os(L^L)2(H2C=CH-C(CH3)( =C(R)(O–)))]+ but not Os-hydride intermediates. Overall, these osmafurans are not directly derived from common metal-allene reaction patterns.