Behavior of OsH₂Cl₂(P^<i>i</i>Pr₃)₂ in Acetonitrile: The Importance of the Small Details

The behavior of OsH2Cl2(PiPr3)2 (1) in acetonitrile as solvent is studied. Acetonitrile coordinates to the metal center of 1 and promotes the dihydride−dihydrogen transformation of its OsH2 unit to give the trans-Cl2 compound OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2a), which evolves to its cis-Cl2 isomer 2b. Treatment of 1 with TlPF6 in acetonitrile leads to the PF6 salt of the cis-bis(acetonitrile) cation [OsCl(η2-H2)(CH3CN)2(PiPr3)2]+ (3a), which is transformed into its trans-bis(acetonitrile) isomer 3b. The addition of Et3N to the PF6 salts of 3a,b in acetonitrile gives [OsH(CH3CN)3(PiPr3)2]PF6 (4). Reaction of 4 with 1,5-cyclooctadiene (COD) in refluxing toluene affords [OsH(COD)(CH3CN)2(PiPr3)]PF6 (5). The X-ray structures of 3b and 5 are also reported.