NDLI: A cw EPR and ENDOR investigation on a series of Cr(I) carbonyl complexes with relevance to alkene oligomerization catalysis: [Cr(CO) $_{4}L]$ $^{+}$ (L = Ph $_{2}PN(R)PPh$ $_{2}$ , Ph $_{2}P(R)PPh$ $

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Hamilton, Tracy Smith, David M. Murphy, Damien M. Hanton, Martin J. Mcdyre, Lucia E. Cavell, Kingsley J. Gabrielli, William F.
Description	Author Affiliation: McDyre LE ( School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, UK CF10 3AT.)
Abstract	The preparation and characterisation of the Cr( I) complexes [Cr(CO) $_{4}L]$ $^{+}$ (L = Ph $_{2}PN(R)PPh$ $_{2}$ , Ph $_{2}P(R)PPh$ $_{2}$ ), which are used as pre- catalysts for the selective oligomerization of ethylene , are reported. The electronic properties and structural features of these complexes in frozen solution have been established via continuous wave X-band Electron Paramagnetic Resonance ( cw-EPR ) and continuous wave $^{1}H,$ $^{14}N$ and $^{31}P$ Electron Nuclear Double Resonance ( cw-ENDOR ) spectroscopy . The EPR spectra are dominated by the g anisotropy, with notably large $^{P}A$ couplings from the two equivalent $^{31}P$ nuclei. The spin Hamiltonian parameters ( g $_{⊥}$ $(g_{xx}$ = $g_{yy})$ > $g_{e}$ > g $_{∥}$ $(g_{zz}))$ are consistent with a low-spin $d^{5}$ system possessing $C_{2v}$ symmetry, with a SOMO where the metal contribution is primarily $d_{xy}$ for all complexes. The isotropic Fermi contact term $(^{P}a_{iso},$ determined by EPR and ENDOR ) was found to be largest for complexes containing ligands e, d, f and g, indicating that the $^{31}P$ 3 s character in the SOMO is higher for the PNP type ligands than the PCP type. Subtle structural differences in the complexes were also identified through variations in the Δ g shifts (identified by EPR ), and through differences in the phenyl ring conformations (identified by $^{1}H$ ENDOR ). Attempts to correlate trends in EPR -derived parameters with data measured for catalysis using these pre- catalysts are also made, but no clear connections were found.
ISSN	14779226
Issue Number	33
Journal	Dalton Trans.
Volume Number	39
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2010-09-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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