| Abstract
| - S-atom abstraction from Os(CS)(PCy3)2Cl2 using Ta(OSi-t-Bu3)3 affords the first terminal carbide complex of osmium, Os(⋮C)(PCy3)2Cl2, and halide exchange yields the second example, Os(⋮C)(PCy3)2I2. Alkylation or acylation of the carbide ligand yields several cationic five-coordinate and neutral six-coordinate carbyne complexes; protonation with HO3SCF3 (HOTf) affords the unstable cationic methylidyne species [Os(⋮CH)(PCy3)2Cl2][OTf].
- The first terminal carbide complex of osmium, Os(⋮C)(PCy3)2Cl2 (4), was synthesized via S-atomabstraction from Os(CS)(PCy3)2Cl2 (4-S) by Ta(OSi-t-Bu3)3 (7). Compound 4 reacts with HO3SCF3 (HOTf)to form the first cationic osmium methylidyne complex [Os(⋮CH)(PCy3)2Cl2][OTf] (18). The analogousruthenium complex [Ru(⋮CH)(H2IMes)(PCy3)Cl2][OTf] is not observed upon protonation of Ru(⋮C)(H2IMes)(PCy3)Cl2 (2) with HOTf. Substitution of the chloride ligands in 4 is surprisingly difficultcompared to the case of 4-S, but Os(⋮C)(PCy3)2I2 can be obtained. Compound 4 also reacts with avariety of electrophiles to afford cationic five-coordinate and neutral six-coordinate carbyne complexes.In general, 4 reacts more readily with electrophiles than does 1, and cationic carbyne complexes formedfrom 4 are more resistant to degradation than are their Ru counterparts.
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