Fourier Transform Carbon - 13 Nuclear Magnetic Resonance Study of LnNi ( CO ) 4 - n Derivatives

13C N M R spectra have been obtained f0r.a series of LnNi(CO)o-n derivatives (n = 0-3) where L = PR3, PPhzY, PPhY2, P(OR')3, and Pc13 (R = Me, Et, Bu, Ph; R' = Me, Et, l-Pr, Ph; Y = C1, Me, OMe, OPh). The effect upon the carbonyl chemical shift of the replacement of X by Y substituents in X3-nYnPNi(C0)3 derivatives appears to be additive, as is the effect of the sequential replacement of carbonyl by phosphorus ligands. An excellent correlation is observed between the carbonyl chemical shifts and either the infrared stretching force constants or Kabachnik's a parameters. These data are analyzed in terms of the electron donor-acceptor abilities of the ligands.