Oxidative Addition of HX (X = H, SiR₃, GeR₃, SnR₃, Cl) Molecules to the Complex Os(<i>η</i>⁵-C₅H₅)Cl(PⁱPr₃)₂

Abstract

The cyclopentadienyl complex Os(η5-C5H5)Cl(PiPr3)2 (1) reacts with molecular hydrogen to give a mixture of the isomers transoid-dihydride OsH2(η5-C5H5)Cl(PiPr3) (2a) and cisoid-dihydride OsH2(η5-C5H5)Cl(PiPr3) (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(η5-C5H5)(PiPr3) (3). In solution, the cisoid hydride ligands of this complex also undergo a thermally activated site exchange process. The activation parameters are ΔH⧧ = 15.1 ± 0.3 kcal·mol-1 and ΔS⧧ = 0.5 ± 0.7 cal·mol-1·K-1. Complex 1 also reacts with group 14 element hydride compounds to afford OsH(η5-C5H5)Cl(ER3)(PiPr3) [ER3 = SiEt3 (4), Si(CH2−CHCH2)Me2 (5), SiPh3 (6), SiHPh2 (7), SiH2Ph (8), GeEt3 (9), GePh3 (10), GeHPh2 (11), SnnBu3 (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 HSnnBu3 to give the dihydride−stannyl derivative OsH2(η5-C5H5)(SnnBu3)(PiPr3) (14). The reaction of 1 with HCl leads to a mixture of the monohydrides OsH(η5-C5H5)Cl2(PiPr3) (15) and [OsH(η5-C5H5)Cl(PiPr3)2]+ (16). Complexes 15 and 16 can also be obtained by reaction of 6 with HCl and by protonation of 1 with HBF4, respectively.