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

Carter, Emma, Collison, David, Edge, Ruth, Fitzgerald, Emma C., Lancashire, Hannah N., Murphy, Damien Martin, McDouall, Joseph J. W., Sharples, Joseph and Whiteley, Mark W. 2010. Experimental observation of spin delocalisation onto the aryl-alkynyl ligand in the complexes [Mo(C=CAr)(Ph2PCH2CH2PPh2)(η-C7H7)]+ (Ar = C6H5, C6H4-4-F; C7H7 = cycloheptatrienyl): an EPR and ENDOR investigation. Dalton Transactions 39 (47) , pp. 11424-11431. 10.1039/c0dt00642d

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Abstract

The paramagnetic aryl-alkynyl complexes [Mo(CCAr)(dppe)(η-C7H7)]+ (dppe = Ph2PCH2CH2PPh2; Ar = C6H5, [1]+; C6D5, [2]+; C6H4-4-F, [3]+; C6H4-4-Me, [5]+) and [Mo(CCBut)(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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: RSC
ISSN: 1477-9226
Funders: EPSRC
Last Modified: 04 Jul 2019 21:25
URI: http://orca.cf.ac.uk/id/eprint/12972

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