Structural consequences of the one-electron reduction of d4 [Mo(CO)2(η-PhCCPh)Tp′]+ and the electronic structure of the d5 radicals [M(CO)L(η-MeCCMe)Tp′] {L = CO and P(OCH2)3CEt}

Christopher J. Adams; Ian M. Bartlett; Supakorn Boonyuen; Neil G. Connelly; David J. Harding; Owen D. Hayward; Eric J. L. McInnes; A. Guy Orpen; Michael J. Quayle; Philip H. Rieger

doi:10.1039/B514951G

Structural consequences of the one-electron reduction of d⁴ [Mo(CO)₂(η-PhCCPh)Tp′]⁺ and the electronic structure of the d⁵ radicals [M(CO)L(η-MeCCMe)Tp′] {L = CO and P(OCH₂)₃CEt}†

Christopher J. Adams,^a Ian M. Bartlett,^a Supakorn Boonyuen,^a Neil G. Connelly,*^a David J. Harding,^a Owen D. Hayward,^a Eric J. L. McInnes,^b A. Guy Orpen,^a Michael J. Quayle^a and Philip H. Rieger ‡^c

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^a School of Chemistry, University of Bristol, Bristol, UK
E-mail: neil.connelly@bristol.ac.uk
Fax: +44 (0)117 929 0509
Tel: +44 (0)117 928 8162

^b School of Chemistry, University of Manchester, Manchester, UK

^c Department of Chemistry, Brown University, Rhode Island, USA

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-RCCR′)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-PhCCPh)Tp′][PF₆] showed that oxidation is accompanied by a lengthening of the CC bond and shortening of the Mo–C_alkyne 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-MeCCMe)Tp′], via nitrile substitution in [Mo(CO)(NCMe)(η-MeCCMe)Tp′], whereas a similar reaction with [M(CO){P(OCH₂)₃CEt}(η-MeCCMe)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-MeCCMe)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 d_yz 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.

Dalton Transactions

Structural consequences of the one-electron reduction of d⁴ [Mo(CO)₂(η-PhCCPh)Tp′]⁺ and the electronic structure of the d⁵ radicals [M(CO)L(η-MeCCMe)Tp′] {L = CO and P(OCH₂)₃CEt}†

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Structural consequences of the one-electron reduction of d⁴ [Mo(CO)₂(η-PhCCPh)Tp′]⁺ and the electronic structure of the d⁵ radicals [M(CO)L(η-MeCCMe)Tp′] {L = CO and P(OCH₂)₃CEt}

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