| Autor: |
Adams, Christopher J., Bartlett, Ian M., Connelly, Neil G., Harding, David J., Hayward, Owen D., Martín, Antonio J., Orpen, A. Guy, Quayle, Michael J., Rieger, Philip H. |
| Zdroj: |
Journal of the Chemical Society, Dalton Transactions; November 14, 2002, Vol. 2002 Issue: 22 p4281-4288, 8p |
| Abstrakt: |
X-Ray structural studies on the redox pair [Cr(CO)2(η-PhC&z.tbd;CPh)(η-C6Me5H)]z (z = 0 and 1) show that one-electron oxidation of the neutral complex results in a shortening of the CrCalkyne bonds and a lengthening of the CrC(O) bonds, consistent with depopulation of a HOMO antibonding with respect to the metalalkyne interaction. Oxidation leads to an increase in the substitutional lability of the CrCO bonds so that [Cr(CO)2(η-RC&z.tbd;CR)(η-C6Me6)]+ (R = Ph or C6H4OMe-p) reacts with Lewis bases to give [Cr(CO)L(η-RC&z.tbd;CR)(η-C6Me6)]+ {L = CNXyl, P(OMe)3 and P(OCH2)3CEt}, X-ray studies on which show a rotation of the alkyne to align with the remaining CrCO bond. ESR spectroscopic studies on [Cr(CO)L(η-RC&z.tbd;CR)(η-C6Me6)]+ show delocalisation of the unpaired electron onto the alkyne ligand, consistent with its description as a three-electron donor. The cations [Cr(CO)L(η-RC&z.tbd;CR)(η-C6Me6)]+ undergo both one-electron reduction and oxidation, and chemical oxidation of [Cr(CO){P(OCH2)3CEt}(η-p-MeOC6H4C&z.tbd;CC6H4OMe-p)(η-C6Me6)]+ with AgPF6 gives the dication [Cr(CO){P(OCH2)3CEt}(η-p-MeOC6H4C&z.tbd;CC6H4OMe-p)(η-C6Me6)]2+. Thus the two-electron alkyne of [Cr(CO)2(η-RC&z.tbd;CR)(η-C6Me6)] is converted into the four-electron alkyne of [Cr(CO)L(η-RC&z.tbd;CR)(η-C6Me6)]2+ by an ECE (E = electrochemical, C = chemical) process in which all of the intermediates have been fully characterised. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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