Synthesis and Characterization of OsH<sub>2</sub>Cl[κ<i>N</i>,κ<i>O</i>-(ONCR<sub>2</sub>)](P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (CR<sub>2</sub> = C(CH<sub>2</sub>)<sub>4</sub>CH<sub>2</sub>, R = CH<sub>3</sub>): Influence of the L<sub>2</sub> Ligand on the Nature of the H<sub>2</sub> Unit in OsH<sub>2</sub>ClL<sub>2</sub>(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (L<sub>2</sub> = ONCR<sub>2</sub>, NHC(Ph)C<sub>6</sub>H<sub>4</sub>) Complexes
作者:Ricardo Castarlenas、Miguel A. Esteruelas、Enrique Gutiérrez-Puebla、Yves Jean、Agustí Lledós、Marta Martín、Jaume Tomàs
DOI:10.1021/om9904192
日期:1999.10.1
The dihydride-dichloro complex OsH2Cl2((PPr3)-Pr-i)(2) (1) reacts with cyclohexanone oxime and acetone oxime in the presence of Et3N to give the dihydride derivatives OsH2Clkappa N,kappa O-[ON=C(CH2)(4)CH2]}(PiPr(3))(2) (2) and OsH2Clkappa N,kappa O-[ON=C(CH3)(2)]}((PPr3)-Pr-i)(2) (3), respectively. The structure of 2 has been determined by X-ray diffraction. The geometry around the osmium atom can be described as a distorted pentagonal bipyramid, with the triisopropylphosphine ligands occupying two relative trans positions. The remaining perpendicular plane is formed by the hydride ligands, the chlorine, and the oximate group, which acts with a bite angle of 36.6(1)degrees. In solution the hydride ligands of 2 and 3 undergo an intramolecular thermally activated site exchange process, The activation parameters off;his process are Delta H-double dagger = 11.9(+/-0.7) kcal mol(-1) and Delta(double dagger) = -0.5(+/-1.4) cal mol(-1) K-1 for 2 and Delta H-double dagger = 11.7(+/-0.8) kcal mol(-1) and Delta S-double dagger = -0.8(+/-2.0) cal mol(-1) K-1 for 3. To understand why complexes 2 and 3 are dihyride derivatives, while the previously reported complex OsCl-NH=C(Ph)C6H4}(eta(2)-H-2)((PPr3)-Pr-i)(2) is an elongated dihydrogen-compound, a quantitative theoretical analysis of the interaction between the H-2 moiety and the OsClL2(PH3)(2)(L-2 = ON=CH2, NH=CHCH=CH) complex fragments, along the oxidative addition pathway, is also reported.