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

The reactions of the trichloro carbyne complexes OsCl 3 (≡CR)(PPh 3 ) 2 (R = CH═CPh 2, CH 2 Ar) with bromine and hydrogen peroxide were studied. Unlike monochloro carbyne complexes OsCl(≡CAr)(CO)(PPh 3 ) 2, the trichloro complexes OsCl 3 (≡CR)(PPh 3 ) 2 do not undergo oxidation reactions at the metal center or the metal–carbyne bond. Treatment of OsCl 3 (≡CCH═CPh 2 )(PPh 3 ) 2 with Br 2 /H 2 O and H 2 O 2 /HCl produced OsBr 3 (≡CCH═CPh 2 )(H 2 O)(PPh 3 ) and OsCl 3 (≡CCCl═CPh 2 )(PPh 3 ) 2, respectively. Reactions of OsCl 3 (≡CCH 2 -C 6 H 4 - p -R)(PPh 3 ) 2 (R = H, CMe 3 ) with H 2 O 2 /HCl or H 2 O 2 gave OsCl 3 {≡CC(O)-C 6 H 4 - p -R}(PPh 3 ) 2 . Computational studies suggest that the difference in the reactivity of OsCl(≡CAr)(CO)(PPh 3 ) 2 and OsCl 3 (≡CR)(PPh 3 ) 2 is mainly of thermodynamic origin.