Oxidative Addition of HX (X = H, SiR₃, GeR₃, SnR₃, Cl) Molecules to the Complex Os(η⁵-C₅H₅)Cl(PⁱPr₃)₂

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−CHCH₂)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.