Nicholas A. Matwiyoff

Donor and acceptor properties of some trisubstituted oxy compounds of the group IV elements

The donor and acceptor properties of the compounds R3MOC6H5 (where R = CH3 or C2H5 and M = C, Si, Ge, Sn and Pb) and C6H5)3MOH were investigated in detail. The results cannot be correlated with the “new” electronegativity scale proposed for the Group IV elements. Changes in the extent of π-bonding between the central element and oxygen are proposed as the dominant effect giving rise to the observed trends. Contrary to previous reports no hydrogen bonding interaction could be detected between (C6H5)3SnOH or (C6H5)3PbOH and (C2H5)2O. The donors (C2H5)2O. (CH3)2SO and HC(O)N(CH3)2 were all investigated in this study. In every instance a reversible dehydration reaction occurred. The infrared spectra of these systems is discussed. It was found that the compounds R3MOH (where R is CH3 or C2H5 and M is tin or lead) could be titrated with phenol in the presence of molecular sieves. This procedure may be of value in the synthesis of group IV compounds which are sensitive to light and heat.

Use of a relationship between J(13CH) and τ to evaluate anisotropic contributions to τ-anisotropies in the τ-values of the group IV tetramethyl derivatives

A linear relationship is reported between 13CH spin-spin coupling constants, J(13CH), and proton chemical shifts, τ, for a restricted series of methyl derivatives. The existence of this relationship is rationalized and the relationship is employed: (a) to justify an earlier interpretation of the chemical shift data for the tetramethyl derivatives of the group IV elements; (b) to conclude that the chemical shift data cannot be employed to evaluate electronegativities of the central group IV element in these compounds; (c) to aid in evaluating the anisotropic contributions to the chemical shifts of the methyl halides and other compounds. The 13CH spin-spin coupling constants indicate that the hybridization of the methyl carbon atom in the tetramethyl derivatives of the group IV elements changes with the effectiveness of central element-carbon overlap.