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Kinetic studies help determine the nature of substitution and geometrical isomerization reactions of the series trans-(Os-II-(en)2(eta2-H2)L), where L is a variable ligand. In aqueous solution, the complex has the composition trans-(Os(en)2(eta2-H2)H2O)2+, with CF2SO(sub 3)(super -) as counter ion and formation constants depending on the nature of donors. In this complex, substitution occurs by elimination of H2O ligand and high activation is necessary for the nucleophile to enter the coordination sphere of the intermediate. A rearrangement to (Os(en)2(H)2)2+, a dihydride of Os(IV), stabilizes the intermediate and isomerization occurs by intramolecular rearrangement. NMR experiments help compare the characteristics of cis and trans isomers.

X-ray and neutron diffraction, which were used to determine the structure of certain osmium compounds, revealed a cation in the compound having a low J(H-D) value of 9.0 Hertz. The acetate and the H2 ligands of the structure were found at positions on opposite sides of the OsN4 plane and induced an octahedral coordination. The compound's ethylenediamine ligands demonstrated a trans arrangement.

Research is presented into anti-Markovnikov arylation catalyzed by a binuclear iridium complex.

Reduction of Os(III)(NH3)4(CF3SO3)3 in a medium of cyclic ether produces a dihydrogen complex of tetraammineosmium(II) having carbene as a coligand. NMR experiments reveal the cis position of the carbene coligand and confirm the presence of eta2-H2 ligand. The dihydrogen complex undergoes a slow decomposition in D2O or CD3OD, generating paramagnetic species.

Chemical oxidation of eta-2-H2 complexes of osmium(II) amines results in monohydrido complexes of Os(IV), and the metal can bear six ligands besides H-. Oxidation in methanol of (Os(NH3)5(eta-2-H2))2+ by FeCp2(CF3SO3) does not involve the release of H2 or NH3.

The synthesis of a stable ethene-ethyne metal complex from the eta2-dihydrogen osmium(II) complex is described. Ethylene was bubbled through a solution of the osmium(II) complex in a nitrogen atmosphereand subsequently heated under N2 at 50 degrees centigrade. Nuclear magnetic resonance spectroscopy was then performed to analyze the decomposition of the compound. Results reveal that the reaction of the eta2-dihydrogen osmium(II) complex with ethyne led to the formation of a trans-bis(ethyne) complex.

The synthesis of osmahexatriene provides more insight into the chemistry of metal carbene complexes. Heating the triflate salt of the osmacyclopentatriene complex Os(en)2(C4Me4) (en = ethylenediamine) in tetrabutylamine yields, upon evaporation of t-BuNH2, a new complex in which the cyclic carbene ligand has isomerized into a conjugated hexatriene. Treatment with hydrochloric acid yields a crystallizable form of the complex. The reaction mechanism involves deprotonation of an alpha-methyl moiety in a 1,2-hydrogen shift that eventually protonates the Os-C single bond.

The preparation and structures of the new metallacyclopentatrienes cis-(Os(C4Me4)(en)2)2+ and cis-(Os(C10H14)(en)2)2+, where en = ethylenediamine, are presented. The first compound is prepared from the reaction of an acetone solution of trans-(Os(en)2(eta2-H2)(H2O))(CF3SO3)2 with 2-butyne, heated at 59 degrees C. The 1H NMR spectrum of the complex reveals that the planar symmetry has been transformed to C2. Meanwhile, the second complex is formed via the intramolecular alkyne cyclization of cis-(Os(C10H14)(en)2)(CF3SO3)2 when treated with 2,8-decadiyne.