Oxidative addition of HX (X = H, SiR3, GeR3, SnR3, Cl) molecules to the complex Os(eta(5)-C5H5)Cl((PPr3)-Pr-i)(2)

The cyclopentadienyl complex Os(eta(5)-C5H5)Cl((PPr3)-Pr-i)(2) (1) reacts w ith molecular hydrogen to give a mixture of the isomers transoid-dihydride OsH2(eta(5)-C5H5)Cl((PPr3)-Pr-i) (2a) and cisoid-dihydride OsH2(eta(5)-C5H5 )Cl((PPr3)-Pr-i) (2b). Isomer 2a has a rigid structure in solution. However , the hydride ligands of 2b undergo a thermally activated site exchange pro cess and show quantum exchange coupling. The reaction of the isomeric mixtu re of 2a and 2b with NaBH4 and methanol leads to the trihydride OsH3(eta(5) -C5H5)((PPr3)-Pr-i) (3) In solution, the cisoid hydride ligands of this com plex also undergo a thermally activated site exchange process. The activati on parameters are Delta H double dagger = 15.1 +/- 0.3 kcal . mol(-1) and D elta S double dagger = 0.5 +/- 0.7 cal . mol(-1) . K-1. Complex 1 also reac ts with group 14 element hydride compounds to afford OsH(eta(5)-C5H5)Cl(ER3 )((PPr3)-Pr-i) [ER3 = SiEt3 (4), Si(CH2-CH=CH2)Me-2 (5), SiPh3 (6), SiHPh2 (7), SiH2-Ph (8), GeEt3 (9), GePh3 (10), GeHPh2 (11), (SnBu3)-Bu-n (12), Sn Ph3 (13)]. The structure of 7 has been determined by an X-ray investigation . The distribution of ligands around the metallic center can be described a s a piano stool geometry with the triisopropylphosphine and diphenylsilyl l igands disposed mutually transoid. Complex 12 reacts with (HSnBu3)-Bu-n to give the dihydride-stannyl derivative OsH2(eta(5)-C5H5)((SnBu3)-Bu-n)((PPr3 )-Pr-i) (14) The reaction of 1 with HCl leads to a mixture of the monohydri des OsH(eta(5)-C5H5)Cl-2((PPr3)-Pr-i) (15) and [OsH(eta(5)-C5H5)Cl((PPr3)-P r-i)(2)](+) (16) Complexes 15 and 16 can also be obtained by reaction of 6 with HCl and by protonation of 1 with HER, respectively.