Mark Underhill

Reactions of dodecacarbonyl-triangulo-triosmium with alkenes and benzene; fluxional behaviour of µ3-(ethan-1-yl-2-ylidyne)-di-µ-hydrido-triangulo-tris(tricarbonylosmium)(3Os–Os)

Ethylene on reaction with Os3(CO)12 heated under reflux in octane undergoes 1,1-elimination of H2 to give the ethan-1-yl-2-ylidyne complex [H2Os3(CH2C)(CO)9], (I), whereas cyclopentene and benzene undergo 1,2-elimination of H2 to give corresponding cyclopenta-1,2-diylidene and cyclohexa-3,5-dien-1,2-diylidene complexes (II) and (III). Kinetic data are given for intramolecular exchange of the –CH2C hydrogen atoms of complex (I) which is faster than hydride exchange, and mechanisms for these processes are discussed. Diphenyl(o-vinyl-phenyl) phosphine (dpvp) reacts with Os3(CO)12 to give the complex [H2Os3(Ph2P·C6H4·C2H)(CO)8], (IV), which is related to the derivatives above.

Reactions of acetylene, methyl- and phenyl-substituted acetylenes, and ethylene with 1,1,1,1,2,2,2,3,3,3-decacarbonyl-2,3-di-µ-hydrido-triangulo-triosmium

Acetylene and substituted acetylenes react with [H2Os3(CO)10] without CO loss at room temperature to give vinyl derivatives of type [HOs3(CR1:CHR2)(CO)10](R1= R2= H or Ph; R1= H, R2= Me or Ph), alkenylene complexes [Os3(CR1:CR2)(CO)10](R1= R2= H or Me; R1= H, R2= Me), and the phenylethynyl complex [HOs3(C2Ph)(CO)10], while other derivatives containing coupled alkynes are formed in low yield, if at all, at room temperature. On heating these complexes in hydrocarbon solvents, hydrogen transfer and CO loss occur to give [H2Os3(C2R2)(CO)9](R = H, Me, or Ph), [HOs3(C2R)(CO)9](R = H or Me), and [HOs3(MeC3H2)(CO)9][in two isomeric forms (A) or (B)]. The dihydrido-complexes may also be prepared by hydrogenation of [Os3-(CR1:CR2)(CO)10](R1= H or Me, R2= Me). Structures are proposed on spectroscopic evidence. The significance of these results to the reactivity of olefins with Os3(CO)12 is discussed.

INSERTION OF ACETYLENE INTO OSMIUM-HYDROGEN BONDS IN CLUSTER COMPLEXES

Bei der Umsetzung des Osmiumcarbonylkomplexes (I) mit den Acetylenen (II) in siedendem Hexan bilden sich die Acetyleneinschubverbindungen (III) und (IV).

Triruthenium and triosmium carbonium derivatives

The preparation and protonation of H2Os3-(CO)9CCH2 and other related complexes are reported.

Some benzyne complexes of osmium derived from dimethylphenylphosphine or dimethylphenylarsine

The complexes [Os3(CO)11(EMe2Ph)] or [Os3(CO)10(EMe2Ph)2](E = P or As) on heating give C6H4-bridged complexes [HOs3(C6H4)(EMe2)(CO)9], [HOs3(C6H4)(PMe2)(PMe2Ph)(CO)8]. [Os3(C6H4)(Eme2)2(CO)7], and [HOs3(Me2PC6H4C6H3)(PMe2)(CO)8]. When E = As, dimeric complexes containing bridging C6H4 are also obtained. Structures and mechanisms of the fluxional behaviour of these complexes are discussed in the light of n.m.r. spectra.

Hydrogenation and fluxional behaviour of H2Os3(CCH2)(CO)9, a vinylidene complex derived from ethylene

Preliminary crystallographic data for the complex H2Os3(CCH2)(CO)9 derived from ethylene and Os3(CO)12 are given and the mechanisms of its fluxional behaviour and hydrogenation to give H3Os3(CCH3)(CO)9 are discussed.