Reactions of elongated dihydrogen-osmium complexes containing orthometalated ketones with alkynes:: Hydride-vinylidene-π-alkyne versus hydride-osmacyclopropene

The trihydride complex OsH3{C6F4C(6)CH3}(PiPr(3))(2) (1) reacts with HBF4.H2O to give the elongated dihydrogen derivative [Os{C6F4C(O)CH3}(eta(2)-H-2)(H2O)((PPr3)-Pr-i)(2)]-BF4 (2), with a separation between the hydrogen atoms of the elongated dihydrogen of about 1.3 Angstrom. Under one atmosphere of acetylene, complex 2 and the related [Os{C6H4C(O)CH3}(eta(2)-H-2)(H2O)((PPr3)-Pr-i)(2)]BF4 (3) afford the hydride-vinylidene-pi-alkyne derivative [OsH(=C=CH2) (eta(2)-HCdropCH)((PPr3)-Pr-i)(2)]BF4 (4), with the alkyne acting as a four-electron donor ligand. Complex 4 reacts with methylmagnesium chloride and acetone oxime. The first reaction gives the allyl derivative OsH(eta(3)-C3H5)(=C=CH2)(PiPr3)2 (5), whereas the second one affords the oximate-carbyne [OsH{kappa-N,kappa-O[ON=C(CH3)(2)]}(dropCCH(3)-((PPr3)-Pr-i)(2)]BF4 (6). Similarly to acetylene, cyclohexyl-acetylene reacts with 2 and 3 to give [OsH(=C=CHCy)-(eta(2)-HCdropCCy)((PPr3)-Pr-i)(2)]BF4 (7), which in solution at room temperature decomposes to a mixture of unidentified products. Complexes 2 and 3 also react with phenylacetylene. The reactions lead to complex mixtures of products containing [OsH(=C=CHPh)(eta(2)-HCdropCPh)- ((PPr3)-Pr-i)(2)]BF4 (8) and [OsH{C6X4C(O)CH3}{C(Ph)CH2}-((PPr3)-Pr-i)(2)]BF4 (X = F (9), H (11)), as main components. In solution at room temperature, complex 8 evolves into the diphenylbutadiene derivative [OsH(eta(4)-C4H4Ph2){[eta(2)-CH2=C(CH3)]((PPr2)-Pr-i}((PPr2Pr)-Pr-i-Pr-n)]BF4 (10)- Complex 11 reacts with acetophenone to afford [OsH{C6H4C(O)-CH3}(2)((PPr3)-Pr-i)(2)]BF4 (12). The X-ray structures of 4, 9, and 10 are also reported.