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A tungsten‐183 NMR study of cis and trans isomers of [W(CO)4(PPh3)(PR3)](PR3 = phosphine, phosphite)

Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, P.O. Wits 2050, South Africa
Magnetic Resonance in Chemistry (Impact Factor: 1.53). 10/2008; 46(S1):S56 - S62. DOI: 10.1002/mrc.2300

ABSTRACT Tungsten-183 NMR data are reported for the complexes cis- and trans-[W(CO)4(PPh3)(PR3)] (PR3 = PnBu3, PMe3, PMe2Ph, PMePh2, PPh3, P(4-C6H4OMe)3, P(4-C6H4Me)3, P(4-C6H4F)3, P(OMe)3, P(OEt)3, P(OPh)3 and for PCy3, P(NMe2)3(trans isomer only). The 183W chemical shift (obtained by indirect detection using 31P) is found to be related to the PR3 ligand parameters ν and θ (Tolman electronic factor and cone angle, respectively) for the cis isomers and to ν (but only poorly to θ) for the trans isomers. The 183W31P spin coupling constant is also related, less clearly for PC than for PN and PO bonded ligands, to ν. Chemical shifts are referenced to an absolute frequency Ξ (183W) = 4.15 MHz, which is proposed as a calibration standard for 183W NMR. The structures of cis-[W(CO)4(PPh3)(PMe3)] and cis-[W(CO)4(PPh3){P(4-C6H4F)3}] are reported. Copyright © 2008 John Wiley & Sons, Ltd.

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