Issue 28, 2006

Structural consequences of the one-electron reduction of d4 [Mo(CO)2(η-PhC[triple bond, length as m-dash]CPh)Tp′]+ and the electronic structure of the d5 radicals [M(CO)L(η-MeC[triple bond, length as m-dash]CMe)Tp′] {L = CO and P(OCH2)3CEt}

Abstract

Reduction of [M(CO)2(η-RC[triple bond, length as m-dash]CR′)Tp′]X {Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate, M = Mo, X = [PF6], R = R′ = Ph, C6H4OMe-4 or Me; R = Ph, R′ = H; M = W, X = [BF4], R = R′ = Ph or Me; R = Ph, R′ = H} with [Co(η-C5H5)2] gave paramagnetic [M(CO)2(η-RC[triple bond, length as m-dash]CR′)Tp′], characterised by IR and ESR spectroscopy. X-Ray structural studies on the redox pair [Mo(CO)2(η-PhC[triple bond, length as m-dash]CPh)Tp′] and [Mo(CO)2(η-PhC[triple bond, length as m-dash]CPh)Tp′][PF6] showed that oxidation is accompanied by a lengthening of the C[triple bond, length as m-dash]C bond and shortening of the Mo–Calkyne bonds, consistent with removal of an electron from an orbital antibonding with respect to the Mo–alkyne bond, and with conversion of the alkyne from a three- to a four-electron donor. Reduction of [Mo(CO)(NCMe)(η-MeC[triple bond, length as m-dash]CMe)Tp′][PF6] with [Co(η-C5H5)2] in CH2Cl2 gives [MoCl(CO)(η-MeC[triple bond, length as m-dash]CMe)Tp′], via nitrile substitution in [Mo(CO)(NCMe)(η-MeC[triple bond, length as m-dash]CMe)Tp′], whereas a similar reaction with [M(CO){P(OCH2)3CEt}(η-MeC[triple bond, length as m-dash]CMe)Tp′]+ (M = Mo or W) gives the phosphite-containing radicals [M(CO){P(OCH2)3CEt}(η-MeC[triple bond, length as m-dash]CMe)Tp′]. ESR spectroscopic studies and DFT calculations on [M(CO)L(η-MeC[triple bond, length as m-dash]CMe)Tp′] {M = Mo or W, L = CO or P(OCH2)3CEt} show the SOMO of the neutral d5 species (the LUMO of the d4 cations) to be largely dyz in character although much more delocalised in the W complexes. Non-coincidence effects between the g and metal hyperfine matrices in the Mo spectra indicate hybridisation of the metal d-orbitals in the SOMO, consistent with a rotation of the coordinated alkyne about the M–C2 axis.

Graphical abstract: Structural consequences of the one-electron reduction of d4 [Mo(CO)2(η-PhC [[triple bond, length as m-dash]] CPh)Tp′]+ and the electronic structure of the d5 radicals [M(CO)L(η-MeC [[triple bond, length as m-dash]] CMe)Tp′] {L = CO and P(OCH2)3CEt}

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2005
Accepted
08 Feb 2006
First published
01 Mar 2006

Dalton Trans., 2006, 3466-3477

Structural consequences of the one-electron reduction of d4 [Mo(CO)2(η-PhC[triple bond, length as m-dash]CPh)Tp′]+ and the electronic structure of the d5 radicals [M(CO)L(η-MeC[triple bond, length as m-dash]CMe)Tp′] {L = CO and P(OCH2)3CEt}

C. J. Adams, I. M. Bartlett, S. Boonyuen, N. G. Connelly, D. J. Harding, O. D. Hayward, E. J. L. McInnes, A. G. Orpen, M. J. Quayle and P. H. Rieger, Dalton Trans., 2006, 3466 DOI: 10.1039/B514951G

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