Oxidative addition of HX (X = H, SiR3, GeR3, SnR3, Cl) molecules to the complex Os(η5-C5H5)Cl(PiPr3)2

The cyclopentadienyl complex Os(eta(5)-C5H5)Cl((PPr3)-Pr-i)(2) (1) reacts with 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 process and show quantum exchange coupling. The reaction of the isomeric mixture 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 complex also undergo a thermally activated site exchange process. The activation parameters are Delta H double dagger = 15.1 +/- 0.3 kcal . mol(-1) and Delta S double dagger = 0.5 +/- 0.7 cal . mol(-1) . K-1. Complex 1 also reacts 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), SnPh3 (13)]. The structure of 7 has been determined by an X-ray investigation. The distribution of ligands around the metallic center can be described as a piano stool geometry with the triisopropylphosphine and diphenylsilyl ligands 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 monohydrides OsH(eta(5)-C5H5)Cl-2((PPr3)-Pr-i) (15) and [OsH(eta(5)-C5H5)Cl((PPr3)-Pr-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.