Spin‐Density Distributions in Conjugated Ligands of Paramagnetic Chelates from NMR Contact Interaction Shifts
                                
                                    
                                        作者:D. R. Eaton、A. D. Josey、W. D. Phillips、R. E. Benson                                    
                                    
                                        DOI:10.1063/1.1701326
                                    
                                    
                                        日期:1962.7.15
                                    
                                    Electron-spin-density distributions in a variety of π systems have been obtained from proton-contact interaction shifts in paramagnetic nickel II chelates of N,N′-disubstituted aminotroponeimines. The results have furnished a great deal of new information regarding the detailed manner in which π electrons are distributed via conjugative effects. Spin-density distributions in these systems calculated by the valence-bond scheme are shown to be in quite good general agreement with experimental determinations. Effects attributable to hyperconjugation have been observed and the conjugating abilities of linking groups C=C, N=N, NH, O, S, and SO2 have been assessed. It is shown also that metal-ligand π-bond formation results in transfer of 0.1 of an unpaired electron from nickel to the π system of each of the ligands of these bischelates.