Stepwise Reductive Acidolysis of OsH4(PMe2Ph)3. Mechanism of Hydrogen Elimination/Ligand Addition

Article abstract of DOI:10.1021/ja00318a019

The polyhydride OsH4(PMe2Ph)3 (1) reacts with either HBF4.OEt2 or Ph3CPF6 and CH3CN to give X2 (6) (X=BF4, PF6).The acidolysis reaction proceeds in stepwise fashion through several intermediate species.Using limiting reagent quantities (acid and CH3CN), it is possible to either isolate or spectrally characterize OsH5(PMe2Ph)3⁺ (2), OsH3(PMe2Ph)3(CH3CN)⁺ (3), mer,cis-OsH(PMe2Ph)3(CH3CN)2⁺ (4), and mer-Os(PMe2Ph)3(CH3CN)3²⁺ (5) on the pathway to 6.Additionally, kinetic and labeling studies indicate that H2 substitution by CH3CN occurs via a preequilibrium H2 loss and subsequent trapping by CH3CN.The X-ray diffraction structure of 6 (X=PF6) is also reported.