Coordination, oligomerisation and transfer hydrogenation of acetylenes by some ruthenium and osmium carboxylates: Crystal and molecular structures of bis(trifluoroacetato)carbonyl-(methanol) bis(triphenylphosphine)ruthenium(II) and (1,4-diphenylbut-1-en-3-yn-2-yl)trifluoroacetato-(carbonyl) bis(triphenylphosphine)ruthenium(II)

The hydrides [MH(O2CCF3)(CO)(PPh3)2] (M = Ru or Os) react with disubstituted acetylenes PhCCPh and PhCCMe to afford vinylic products [M{C(Ph)CHPh}(O2CCF3)(CO)(PPh3)2] and [M{C(Ph)CHMe}(O2CCF3)(CO) (PPh3)2]/[M{C(Me)CHPh}(O2CCF3)(CO)(PPh3)2] respectively. Acidolysis of these products with trifluoroacetic acid in cold ethanol liberates cis-stilbene and cis-PhHCCHMe respectively thus establishing the cis-stereochemistry of the vinylic ligands. The complexes [M(O2CCF3)2(CO)(PPh3)2] formed during the acidolysis step undergo facile alcoholysis followed by β-elimination of aldehyde to regenerate the parent hydrides [MH(O2CCF3)(CO)(PPh3)2] and thereby complete a catalytic cycle for the transfer hydrogenation of acetylenes. The molecular structure of the methanol-adduct intermediate, [Ru(O2CCF3)2(MeOH)(CO)(PPh3)2] has been determined by X-ray methods and shows that the coordinated methanol is involved in H-bonding with the monodentate trifluoroacetate ligand [MEO-H---OC(O)CF3; O...O = 2.54 A]. The hydrides [MH(O2CCF3)(CO) (PPh3)2]react with 1,4-diphenylbutadiyne to afford the complexes [M{C(CCPh)CHPh} (O2CCF3)(CO)(PPh3)2]. The ruthenium product, which has also been obtained by treatment of [RuH(O2CCF3)(CO)(PPh3)2] with phenylacetylene, has been shown by X-ray diffraction methods to contain a 1,4-diphenylbut-1-en-3-yn-2-yl ligand. The osmium complexes [Os(O2CCF3)2(CO)(PPh3)2], [OsH(O2CCF3)(CO)(PPh3)2] and [Os{C(CCPh)CHPh}(O2CCF3)(CO)(PPh3)2] all serve as catalysts for the oligomerisation of phenylacetylene. Acetylene reacts with [Ru(O2CCF3)2(CO)(PPh3)2] in ethanol to afford the vinyl complex [Ru(CHCH2)(O2CCF3)(CO)(PPh3)2].