Oxidative Addition of HX (X = H, SiR3, GeR3, SnR3, Cl) Molecules to the Complex Os(η5-C5H5)Cl(PiPr 3)2

Article abstract of DOI:10.1021/om990235n

The cyclopentadienyl complex Os(η⁵-C₅H₅)Cl(PⁱPr ₃)₂ (1) reacts with molecular hydrogen to give a mixture of the isomers transoid-dihydride OsH₂(η⁵-C₅H₅)Cl(P ⁱPr₃) (2a) and cisoid-dihydride OsH₂(η⁵-C₅H₅)Cl(P ⁱPr₃) (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)(P ⁱPr₃) (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)(P ⁱPr₃) [ER₃ = SiEt₃ (4), Si(CH₂-CH=CH₂)Me₂ (5), SiPh₃ (6), SiHPh₂ (7), SiH₂-Ph (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)(Sn ⁿBu₃)(PⁱPr₃) (14). The reaction of 1 with HCl leads to a mixture of the monohydrides OsH(η⁵-C₅H₅)Cl₂(P ⁱPr₃) (15) and [OsH(η⁵-C₅H₅)Cl(PⁱPr ₃)₂]⁺ (16). Complexes 15 and 16 can also be obtained by reaction of 6 with HCl and by protonation of 1 with HBF₄, respectively.