Orbital interactions in selenomethyl-substituted pyridinium ions and carbenium ions with higher electron demand

Abstract

Computational, solution phase, and crystal structure analysis of 2- and 4-organoselenylmethyl-substituted pyridinium ions (10a-c and 11a-c) provides strong evidence for C-Se hyperconjugation (σC-Se -π*) between the C-Se σ-bond and the π-deficient aromatic ring and a through-space interaction (nSe -π*) between the selenium p-type lone pair and the π-deficient aromatic ring. There is also a weak anomeric-type interaction (nSe- -π*CC) involving the selenium p-type lone pair electrons and the polarized CH 2-C(Ar) σ-bond. NBO analysis of calculated cations with varying electron demand (B3LYP/6-311〈 〈 G**) show that C-Se hyperconjugation (σC-Se -π*) is the predominant mode of stabilization in the ..