Abstract: | A study by titrimetric methods of the donor strength of pyridine and aniline and some of their para -substituted derivatives, and the J (119Sn–C–H) of their adducts with dimethyltin dichloride in nitrobenzene, has shown that the p K b of a Lewis base and its para -substituted derivatives varies linearly with the J (119Sn–C–H) of the adducts of dimethyltin dichloride (Me2SnCl2), with the Lewis base dissolved in an inert solvent. A graphical plot of the p K b of a given series of Lewis bases versus the J (Sn–C–H) of their complexes with Me2SnCl2 in nitrobenzene (at the same temperature, and same complex concentration) gives a straight line with a negative gradient, making possible the deduction of the other parameter (e.g. p K b) for a Lewis base in the series, where the one parameter (e.g. J (Sn–C–H) is known. The graph for each series of Lewis base has its own characteristic gradient, and the gradients appear proportional in magnitude to the donor strengths of each class of the bases, making it possible to deduce from such graphs which series of Lewis bases are the stronger donors. |