Reaction of molecular hydrogen (H2) with chlorohydridoiridium phosphines IrHCl2P2 (P = PPr-iso3 or PBu-tert2Ph): stereoelectronic control of the stability of molecular H2 transition metal complexes
| Autor: | Kenneth G. Caulton, Vladimir I. Bakhmutov, Alberto Albinati, Eric Clot, Dmitry G. Gusev, Vladimir V. Grushin, Odile Eisenstein, Juergen Eckert, Bryan E. Hauger |
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| Rok vydání: | 1993 |
| Předmět: |
010405 organic chemistry
Stereochemistry Chemistry Neutron diffraction General Chemistry Crystal structure 010402 general chemistry 01 natural sciences Biochemistry Catalysis 3. Good health 0104 chemical sciences Bond length Crystallography Colloid and Surface Chemistry Molecular geometry Transition metal Ab initio quantum chemistry methods X-ray crystallography Electronic effect |
| Zdroj: | Journal of the American Chemical Society. 115:7300-7312 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja00069a032 |
| Popis: | IrHCl[sub 2]P[sub 2] (P = P[sup i]Pr[sub 3]) reacts rapidly with H[sub 2] at 25[degrees]C to set up an equilibrium where H[sub 2] binds trans to the original hydride ligand (trans-2). A second slower reaction forms IrH(H[sub 2])Cl[sub 2]P[sub 2] (cis-2), where the cis disposition of the chlorides, and also H cis to H[sub 2], was established by neutron diffraction. This molecule (unlike trans-2), shows rapid site exchange between coordinated H and H[sub 2]. cis-2 can be induced to lose HCL to form Ir(H)[sub 2]ClP[sub 2]. The structure of Ir(H)[sub 2]Cl(P[sup t]Bu[sub 2]Ph)[sub 2], an analog of 3, was shown by neutron diffraction to have a planar H[sub 2]IrCl in a Y shape, with Cl at the base of the Y and a H-Ir-H angle of only 73[degree]. ECP ab initio calculations of IrH[sub 2]Cl(PH[sub 3])[sub 2] show that the Y shape with a H-Ir-H angle close to the experimental value has the minimum energy. They also show that the trans-2 isomer of IrH(H[sub 2])Cl[sub 2](PH[sub 3])[sub 2] is less stable than the cis-2 isomer by 10.3 kcal/mol. The Ir-H[sub 2] interaction is stronger in cis-2. The rotational barrier has been calculated in the two isomers as 2.3 (trans) andmore » 6.5 (cis) kcal/mol. In agreement with the experimental structure, the H-H bond is found to eclipse preferentially the Ir-H bond in cis-2. 74 refs., 12 figs., 5 tabs.« less |
| Databáze: | OpenAIRE |
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