The role of virtual halogen d orbitals in the stability and reactivity of rhenium alkyl halide complexes of the form [(.eta.5-C5H5)Re(NO)(PPh3)(XR)]+
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The electronic structure of the transition-metal Lewis acid [(η5-C5H5)Re(NO)(PPh3)]+ and its coordination to the Lewis bases I−, ICH3, and CH2Cl2 are investigated via Fenske-Hall molecular orbital calculations on the prototype species [(η5-C5H5)Re(NO)(PH3)]+. In each case, electron density is transferred from the ligand to the metal center in a classic Lewis acid-base interaction. The alkyl halide ligands alkylate a variety of nucleophiles, and the reaction coordinate for these processes is studied. From the calculations it is revealed that extra virtuald orbitals must be included in the basis set of the halogen atoms in order to explain the reaction chemistry. Use of this extended basis set places a significant portion of the LUMO's wave function on the halogen atom, as suggested by experiment. The activation of halocarbon ligands occurs as a consequence of the character and geometry of the lowest virtual levels of the complexes and not a prior weakening due to coordination with the metal. © 1989, American Chemical Society. All rights reserved.
author list (cited authors)
Czech, P. T., Gladysz, J. A., & Fenske, R. F.