Nuclear Magnetic Resonance Spectroscopy. Carbon-13 Spectra of n-Alkyl Nickel(II) Aminotroponiminates

In a previous communication from these laboratories we reported the ^(13)C nmr spectrum of nickel(II) N,N'-di(p-tolyl)aminotroponiminate and proposed that, at least qualitatively, the ^(13)C isotropic shifts were consistent with the propagation of unpaired spin density by way of both the π and σ electrons of the ligand. This analysis assumed that the π contribution to the ^(13)C hyperfine coupling constant, ɑ^c_i, could be approximated by the Karplus-Fraenkel equation (eq 1), where S^c is the proportionality factor for the polarization of the 1s electrons and the Q's are the proportionality factors for the 2s electrons