Influence of the heteroatom on the structure, bonding and ring strain of a series of three-membered rings containing a second, third, fourth and fifth row elements: a theoretical investigation

Abstract

Three-membered heterorings have received a great interest for the design of organic reactions and new active therapeutic agents. However, there is little information available in the literature about their structural properties, in particular for those containing third, fourth, and fifth row elements. With this in mind, structure, bonding, ring strain, and Mulliken charge distribution of a series of 22 saturated three-membered rings containing a second, third, fourth, and fifth row element were theoretically investigated. Calculations were carried out within the MP2, PBE1PBE, and CCSD approximations using Pople’s and correlation consistent basis sets. In general, structural predictions obtained by MP2 and coupled cluster are comparable with each other for the studied heterocycles, and their predictions are in good agreement with the little experimental data available. The structural parameters, ring strain, and Mulliken charges are strongly affected by the nature of heteroatom contained into ring skeleton, finding a consistent periodic relationship according to the row-group or row-period plot. The ring geometry was highly symmetric in most of the studied cases (C2h), except for the rings containing V-group elements (Cs) whose molecular symmetry is distorted by the disposition out of molecular plane of H-heteroelement bond. Finally, the increase of heteroatomic radius increases significantly the molecular strain of these three-membered heterocycles, being especially notable in the four and fifth row element rings. Curiously, the rings containing tellurium, iodium, bromo, chloro, and sulfur presented a ring strain comparable to those common heterocycles containing second row element.