A tungsten-183NMR study of cis and trans isomers of [W(CO)4(PPh3)(PR3)](PR3 = phosphine, phosphite).
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 nu and theta (Tolman electronic factor and cone angle, respectively) for the cis isomers and to nu (but only poorly to theta) for the trans isomers. The 183W-31P spin coupling constant is also related, less clearly for P-C than for P-N and P-O bonded ligands, to nu. Chemical shifts are referenced to an absolute frequency Xi (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.
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, P.O. Wits 2050, South Africa. laurence.carlton@wits.ac.za
Laurence
L
Carlton
Avril
A
Emdin
Andreas
A
Lemmerer
Manuel A
MA
Fernandes
D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009942:Organometallic Compounds / Q000737:chemistry*; D010720:Phosphines; D017905:Phosphites; D013237:Stereoisomerism; D014414:Tungsten / Q000737:chemistry*
D008024:Ligands; D009942:Organometallic Compounds; D010720:Phosphines; D017905:Phosphites; D014414:Tungsten