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 ORCID: https://orcid.org/0000-0001-6691-2377, Collison, David, Edge, Ruth, Fitzgerald, Emma C., Lancashire, Hannah N., Murphy, Damien Martin ORCID: https://orcid.org/0000-0002-5941-4879, 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:	03 Dec 2022 11:19
URI:	https://orca.cardiff.ac.uk/id/eprint/12972

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