Hydrogen migration and HCl elimination promoted by metal-centered nucleophilic attack on osmium hydrido-carbynes

The carbynes [OsHCl2(CCH2R)L-2] (R=Ph, CH3; L=(PPr3)-Pr-i) react with CO to give, after 1,2-hydride migration from osmium to C-alpha of the carbyne ligand, the osmium carbene complexes [OsCl2(CO)(=CHCH2R)L-2]. For R=Ph, reactions with excess CO lead to HCl elimination to form. [OsCl(CO)(2)((E)-CH=CHPh)L-2], which reacts with liberated HCl at C-alpha to yield [OsCl2(CO)(2)L-2] and CH2=CHPh. Abstraction of chloride from either the carbynes or carbenes with NaBAr4' (Ar'=3,5-C6H3(CF3)(2)) yields the corresponding coordinatively unsaturated carbyne and carbene complexes [OsHCl(CCH2R)L-2][BAr'(4)] and [OsCl(CO)(=CHCH2R)L-2][BAr'(4)], respectively. The carbynes [OsHCl(CCH2Ph)L-2](+) react with reagent L'(L'=CO, HCCR') to initially give the carbenes [OsCl(L')(=CHCH2Ph)L-2](+) after 1,2-hydride migration to C-alpha of the carbyne ligand. These carbenes react further, eliminating HCl and undergoing selective protonation to yield either [OsCl(CO)(3)L-2](+) and CH2=CHPh (with L'=CO) or the sigma-vinyl carbyne complexes [OsCl(CCH2R')((E)-CH=CHPh)L-2](+) (with L'=HCCR').