Reactions of Os(eta(5)-C5H5)Cl((PPr3)-Pr-i)(2) with NH=CPh2 and PPh3: The unit Os(eta(5)-C5H5)((PPr3)-Pr-i) as support for the study of the competitive alkane-arene intramolecular C-H activation

The cyclopentadienyl complex Os(eta(5)-C5H5)Cl((PPr3)-Pr-i)(2) (1) reacts w ith benzophenone imine to give the cationic orthometalated derivative [OsH( eta(5)-C5H5){NH=C(Ph)C6H4}((PPr3)-Pr-i)]Cl (2a), containing the hydride lig and and the metalated phenyl group mutually cisoid disposed. Treatment of 2 a with NaOCH3 affords the neutral species Os(eta(5)-C5H5){NH=C(Ph)C6H4}- (( PPr3)-Pr-i) (3), which by protonation with HBF4. OEt2 gives [OsH(eta(5)-C5H 5){NH=C(Ph)C6H4)((PPr3)-Pr-i)]BF4 (4). The structure of 4 was determined by an X-ray investigation. The geometry around the osmium center can be descr ibed as a four-legged piano-stool geometry, with the hydride ligand transoi d disposed to the metalated phenyl group and cisoid to the NH of the imine. The separation between the hydride and the NH hydrogen atom is about 2.5 A ngstrom. Complex 1 also reacts with triphenylphosphine. In this case the re action product is the mixed-ligand compound Os(eta(5)-C5H5)Cl(PPh3)((PPr3)- Pr-i) (5). Treatment of 5 with TlPF6 affords the orthometalated triphenylph osphine derivative [OsH(eta(5)-C5H5)(PPh2C6H4)((PPr3)-Pr-i)]PF6 (6) The str ucture of 6 was also determined by an X-ray investigation. As for 4, the ge ometry around the osmium center can be described as a four-legged piano-sto ol geometry with the hydride ligand and the metalated phenyl group in trans oid positions. Treatment of 6 with NaOCH3 produces the extraction of the hy dride ligand and the formation of the neutral species Os(eta(5)-C5H5)(PPh2C 6H4)((PPr3)-Pr-i) (7), which in methanol under reflux gives OsH(eta(5)-C5H5 )(PPh3)((PPr3)-Pr-i) (8). Protonation of 8 with HBF4. OEt2 affords the cati onic dihydride [OsH2(eta(5)-C5H5)(PPh3)((PPr3)-Pr-i)]BF4 (9).