Reactions of Osmium Carbyne Complexes OsCl3(≡CR)(PPh3)2 (R = CH═CPh2, CH2Ar) with Bromine and Hydrogen Peroxide

Abstract

The reactions of the trichloro carbyne complexes OsCl3(≡CR)(PPh3)2 (R = CH═CPh2, CH2Ar) with bromine and hydrogen peroxide were studied. Unlike monochloro carbyne complexes OsCl(≡CAr)(CO)(PPh3)2, the trichloro complexes OsCl3(≡CR)(PPh3)2 do not undergo oxidation reactions at the metal center or the metal–carbyne bond. Treatment of OsCl3(≡CCH═CPh2)(PPh3)2 with Br2/H2O and H2O2/HCl produced OsBr3(≡CCH═CPh2)(H2O)(PPh3) and OsCl3(≡CCCl═CPh2)(PPh3)2, respectively. Reactions of OsCl3(≡CCH2-C6H4-p-R)(PPh3)2 (R = H, CMe3) with H2O2/HCl or H2O2 gave OsCl3{≡CC(O)-C6H4-p-R}(PPh3)2. Computational studies suggest that the difference in the reactivity of OsCl(≡CAr)(CO)(PPh3)2 and OsCl3(≡CR)(PPh3)2 is mainly of thermodynamic origin.