Synthesis and Characterization of OsX{NH=C(Ph)C6H4}H2(PiPr3)2 (X = H, Cl, Br, I): Nature of the H2 Unit and Its Behavior in

详细信息    查看全文

• 作者：Guada Barea ; Miguel A. Esteruelas ; Agustí ; Lledó ; s ; Ana M. Ló ; pez ; Enrique Oñ ; ate ; and José ; I. Tolosa
• 刊名：Organometallics
• 出版年：1998
• 出版时间：August 31, 1998
• 年：1998
• 卷：17
• 期：18
• 页码：4065 - 4076
• 全文大小：245K
• 年卷期：v.17,no.18(August 31, 1998)
• ISSN：1520-6041

文摘

The hexahydride OsH₆(PⁱPr₃)₂ (1) reacts with benzophenone imine to give the trihydridederivative OsH₃{NH=C(Ph)C₆H₄}(PⁱPr₃)₂ (2). The three hydride ligands and the bidentategroup of 2 are situated in the equatorial plane of a pentagonal-bipyramidal arrangement ofligands around the metallic center. In solution, two thermally activated exchange processestake place between these hydride ligands, one of them faster than the other one. The reactionof 2 with HCl leads to OsH₃Cl(NH=CPh₂)(PⁱPr₃)₂ (3), which evolves in solution into theelongated dihydrogen compound OsCl{NH=C(Ph)C₆H₄}(²-H₂)(PⁱPr₃)₂ (4). Complex 4 andthe related compounds OsX{NH=C(Ph)C₆H₄}(²-H₂)(PⁱPr₃)₂ (X = Br (5), I (6)) can be alsoprepared by protonation of 2 with HBF₄·OEt₂ in dichloromethane and subsequent treatmentwith NaX (X = Cl, Br, I). The structure of 4 has been determined by X-ray diffraction. Thegeometry around the osmium atom can be described as a distorted octahedron, with thetriisopropylphosphine ligands occupying two relative trans positions. The remainingperpendicular plane is formed by the mutually cis disposed chloro and dihydrogen ligandsand the metalated benzophenone imine group, which has a bite angle of 75.1(1). The H₂unit of 4-6 shows a restricted rotational motion in solution. Thus, the ¹H NMR spectra inthe high-field region are a function of the temperature. Lowering the sample temperatureleads to a broadening of the dihydrogen resonances. At 213 K, decoalescence occurs, and at193 K, two signals are clearly observed. Theoretical calculations suggest that the transitionstates for the hydrogen exchanges in 2 and 4-6 present dihydrogen-like nature.