Cyclometalated Osmium Complexes Containing a Tridentate PCP Ligand

Reactions between [Et 4 N] 2 OsCl 6 and 1,3-(CH 2 PBu t 2 ) 2 C 6 H 4 afforded the 16-e chloride complexes OsCl(CO)(PCP) ( 1 ) and OsH 2 Cl(PCP) ( 2 ) (PCP = [2,6-(CH 2 PBu t 2 ) 2 C 6 H 3 ] - ) in methanol/isoamyl alcohol and 2-propanol, respectively. The iodide OsH 2 I(PCP) ( 3 ) was obtained from 2 in methyl iodide. Treatment of 1 and 2 with [BH 4 ] - gave the hydride and dihydrogen compounds OsH(CO)(PCP) ( 4 ), OsH(H 2 )(CO)(PCP) ( 5 ), and OsH 3 (H 2 )(PCP) ( 6 ), while formation of the dihydrogen complexes Os(H 2 ) 2 Cl(PCP) ( 7a ) and OsH 2 (H 2 )Cl(PCP) ( 7b ) was observed by NMR in solution of 2 under H 2 . The structures of 1, 2, and 3 were determined by X-ray crystallography.