[H(EtOH)<sub>2</sub>][{OsCl(η<sup>4</sup>-COD)}<sub>2</sub>(μ-H)(μ-Cl)<sub>2</sub>] as an Intermediate for the Preparation of [OsCl<sub>2</sub>(COD)]<sub><i>x</i></sub> and Its Activity as an Ionic Hydrogenation and Etherification Catalyst
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Complex [H(EtOH)2][{OsCl(η4-COD)}2(μ-H)(μ-Cl)2] (1) reacts with 1-hexene, acetone, and acetophenone to give the corresponding reduced organic substrates and the osmium polymer [OsCl2(COD)]x (2, COD = 1,5-cyclooctadiene), which regenerates 1 in ethanol. The reaction of 2 with acetonitrile leads to the mononuclear derivative OsCl2(η4-COD)(CH3CN)2 (3). On the other hand, treatment of 1 with acetonitrile affords the neutral dimer {Os(CH3CN)(η4-COD)}(μ-H)(μ-Cl)2{OsCl(η4-COD)} (4), which has been characterized by X-ray diffraction analysis. The reaction of 4 with triisopropylphosphine gives {Os(Pi-Pr3)(η4-COD)}(μ-H)(μ-Cl)2{OsCl(η4-COD)} (5). Complex 1 is an active catalyst for the ionic hydrogenation of aldehydes and ketones, using 2-propanol as hydrogen source. The reductions of aromatic compounds are easier than those of aliphatic ones, and the hydrogenations of aldehydes are also easier than those of ketones. Complex 1 also promotes the alcohol etherification and one-pot synthesis of isopropyl ethers starting from 2-propanol and the corresponding aldehyde or ketone through catalytic hydrogenation−etherification tandem processes.
