Reactions of Re2Cl4(dppm)2 with carbon monoxide that proceed with retention of the metal-metal bond: synthesis of Re2Cl4(dppm)2(CO)n (n = 1, 2) and the structural characterization of Cl2Re(.mu.-Cl)(.mu.-CO)(.mu.-dppm)2ReCl(CO) Academic Article uri icon

abstract

  • The triply bonded dirhenium(II) complex Re2Cl4(dppm)2(dppm = bis(diphenylphosphino)methane) reacts with carbon monoxide to give the carbonyl complexes Re2Cl4(dppm)2(CO)n(n = 1 or 2). These results provide for the first time evidence as to the nature of the intermediates that are formed in the cleavage of the electron-rich metal-metal triple bond (σ2π4δ2δ*2configuration) by π-acceptor ligands. The neutral complex, Cl2Re(μ-Cl)(μ-CO)(μ-dppm)2ReCl(CO), which has been characterized by X-ray diffraction, crystallizes in the monoclinic system, space group C2/c, with a = 22.877 (6) Å, b = 11.044 (3) Å, c = 22.726 (5) Å, β = 123.02 (2)°, V= 4814 (4) Å3, and Z = 4. The crystal structure was refined to residuals of R = 0.0298, Rw= 0.0285, and quality-of-fit - 1.043. The Re-Re bond distance is 2.584 (1) A, and the molecule comprises a pair of distorted, edge-sharing octahedra. The bridging and terminal Cl and CO ligand sites are disordered in a well-defined manner. A comparison of the spectroscopic properties (IR, and 1H, 31P{1H} and 13C[1H] NMR) of the dicarbonyl complex with those of its 13CO labeled analogue accord with the structure found in the solid state, although 31P{1H} and 13C{1H} NMR spectroscopy show that there is a fluxional process that renders the carbonyl ligands equivalent between room temperature and ca. -20 °C. The monocarbonyl has been shown by IR spectroscopy to exist as a mixture of two isomers both in the solid state and in solution. The NMR spectral properties of this complex (1H, 31P{1H}, and 13C{1H} are consistent with an A-frame A-frame fluxionality that keeps the CO ligand bound to a single rhenium atom only. © 1985, American Chemical Society. All rights reserved.

author list (cited authors)

  • Cotton, F. A., Daniels, L. M., Dunbar, K. R., Falvello, L. R., Tetrick, S. M., & Walton, R. A

complete list of authors

  • Cotton, F Albert||Daniels, Lee M||Dunbar, Kim R||Falvello, Larry R||Tetrick, Stephen M||Walton, Richard A

publication date

  • January 1, 2012 11:11 AM