Behavior of OsH2Cl2(PiPr3)2 in Acetonitrile: The Importance of the Small Details

The behavior of OsH 2 Cl 2 (P i Pr 3 ) 2 ( 1 ) in acetonitrile as solvent is studied. Acetonitrile coordinates to the metal center of 1 and promotes the dihydride−dihydrogen transformation of its OsH 2 unit to give the trans -Cl 2 compound OsCl 2 (η 2 -H 2 )(CH 3 CN)(P i Pr 3 ) 2 ( 2a ), which evolves to its cis -Cl 2 isomer 2b . Treatment of 1 with TlPF 6 in acetonitrile leads to the PF 6 salt of the cis -bis(acetonitrile) cation [OsCl(η 2 -H 2 )(CH 3 CN) 2 (P i Pr 3 ) 2 ] + ( 3a ), which is transformed into its trans -bis(acetonitrile) isomer 3b . The addition of Et 3 N to the PF 6 salts of 3a, b in acetonitrile gives [OsH(CH 3 CN) 3 (P i Pr 3 ) 2 ]PF 6 ( 4 ). Reaction of 4 with 1,5-cyclooctadiene (COD) in refluxing toluene affords [OsH(COD)(CH 3 CN) 2 (P i Pr 3 )]PF 6 ( 5 ). The X-ray structures of 3b and 5 are also reported.