507491-27-2Relevant academic research and scientific papers
Redox routes to arenechromium complexes of two-, three- and four-electron alkynes: Structure and bonding in paramagnetic [Cr(CO)L(η-RC≡CR)(η-arene)]+
Adams, Christopher J.,Bartlett, Ian M.,Connelly, Neil G.,Harding, David J.,Hayward, Owen D.,Martin, Antonio J.,Orpen, A. Guy,Quayle, Michael J.,Rieger, Philip H.
, p. 4281 - 4288 (2008/10/08)
X-Ray structural studies on the redox pair [Cr(CO)2(η-PhC≡CPh)(η-C6Me5H)] z (z = 0 and 1) show that one-electron oxidation of the neutral complex results in a shortening of the Cr-Calkyne bonds and a lengthening of the Cr-C(O) bonds, consistent with depopulation of a HOMO antibonding with respect to the metal-alkyne interaction. Oxidation leads to an increase in the substitutional lability of the Cr-CO bonds so that [Cr(CO)2-(η-RC≡CR)(η-C6Me6)] + (R = Ph or C6H4OMe-p) reacts with Lewis bases to give [Cr(CO)L(η-RC≡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 Cr-CO bond. ESR spectroscopic studies on [Cr(CO)L(η-RC≡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≡CR)(η-C6Me6)]+ undergo both one-electron reduction and oxidation, and chemical oxidation of [Cr(CO){P(OCH2)3CEt} (η-p-MeOC6H4C≡CC6H4OMe-p)( η-C6Me6)]+ with AgPF6 gives the dication [Cr(CO){P(OCH2)3CEt}(η-p-MeOC6H4 C≡CC6H4OMe-p)(η-C6Me6)] 2+. Thus the two-electron alkyne of [Cr(CO)2-(η-RC≡CR)(η-C6Me6)] is converted into the four-electron alkyne of [Cr(CO)L(η-RC≡CR)(η-C6Me6)]2+ by an ECE (E = electrochemical, C = chemical) process in which all of the intermediates have been fully characterised.
