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Issue 47, 2010
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Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C[triple bond, length as m-dash]CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation

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Abstract

The paramagnetic aryl-alkynyl complexes [Mo(C[triple bond, length as m-dash]CAr)(dppe)(η-C7H7)]+ (dppe = Ph2PCH2CH2PPh2; Ar = C6H5, [1]+; C6D5, [2]+; C6H4-4-F, [3]+; C6H4-4-Me, [5]+) and [Mo(C[triple bond, length as m-dash]CBut)(dppe)(η-C7H7)]+ [4]+, have been investigated in a combined EPR and ENDOR study. Direct experimental evidence for the delocalisation of unpaired spin density over the framework of an aryl-alkynyl ligand has been obtained. The X-band solution EPR spectrum of the 4-fluoro derivative, [3]+, exhibits resolved hyperfine coupling to the remote para position of the aryl group [aiso(19F) = 4.5 MHz, (1.6 G)] in addition to couplings attributable to 95/97Mo, 31P and 1H of the C7H7 ring. A full analysis of the 1H ENDOR spectra is restricted by the low g anisotropy of the system which prevents the use of orientation selection. However, inter-comparison of the 1H cw-ENDOR frozen solution spectra of [1]+, [2]+, [4]+ and [5]+, combined with spectral simulation informed by calculated values derived from DFT investigations, has facilitated estimation of the experimental aiso(1H) hyperfine couplings of [1]+ including the ortho, ±3.7 MHz (±1.3 G) and para, ±3.9 MHz (±1.4 G) positions of the C6H5 substituent of the aryl-alkynyl ligand.

Graphical abstract: Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C [[triple bond, length as m-dash]] CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation

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Supplementary files

Article information


Submitted
11 Jun 2010
Accepted
23 Sep 2010
First published
27 Oct 2010

Dalton Trans., 2010,39, 11424-11431
Article type
Paper

Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C[triple bond, length as m-dash]CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation

E. Carter, D. Collison, R. Edge, E. C. Fitzgerald, H. N. Lancashire, D. M. Murphy, J. J. W. McDouall, J. Sharples and M. W. Whiteley, Dalton Trans., 2010, 39, 11424
DOI: 10.1039/C0DT00642D

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