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

The cyclopentadienyl complex Os( η 5 -C 5 H 5 )Cl(P i Pr 3 ) 2 ( 1 ) reacts with molecular hydrogen to give a mixture of the isomers transoid-dihydride OsH 2 ( η 5 -C 5 H 5 )Cl(P i Pr 3 ) ( 2a ) and cisoid-dihydride OsH 2 ( η 5 -C 5 H 5 )Cl(P i Pr 3 ) ( 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 NaBH 4 and methanol leads to the trihydride OsH 3 ( η 5 -C 5 H 5 )(P i Pr 3 ) ( 3 ). In solution, the cisoid hydride ligands of this complex also undergo a thermally activated site exchange process. The activation parameters are Δ H ⧧ = 15.1 ± 0.3 kcal·mol - 1 and Δ S ⧧ = 0.5 ± 0.7 cal·mol - 1 ·K - 1 . Complex 1 also reacts with group 14 element hydride compounds to afford OsH( η 5 -C 5 H 5 )Cl(ER 3 )(P i Pr 3 ) [ER 3 = SiEt 3 ( 4 ), Si(CH 2 −CH CH 2 )Me 2 ( 5 ), SiPh 3 ( 6 ), SiHPh 2 ( 7 ), SiH 2 Ph ( 8 ), GeEt 3 ( 9 ), GePh 3 ( 10 ), GeHPh 2 ( 11 ), Sn n Bu 3 ( 12 ), SnPh 3 ( 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 HSn n Bu 3 to give the dihydride−stannyl derivative OsH 2 ( η 5 -C 5 H 5 )(Sn n Bu 3 )(P i Pr 3 ) ( 14 ). The reaction of 1 with HCl leads to a mixture of the monohydrides OsH( η 5 -C 5 H 5 )Cl 2 (P i Pr 3 ) ( 15 ) and [OsH( η 5 -C 5 H 5 )Cl(P i Pr 3 ) 2 ] + ( 16 ). Complexes 15 and 16 can also be obtained by reaction of 6 with HCl and by protonation of 1 with HBF 4, respectively.