Structure and Bonding of 1,2,4-Triazole Thiones Derived from Nitron

The molecular structures of two 1,2,4-triazole thiones derived from Nitron, namely Nitron(S) and Nitron(S)(Me), have been determined by single crystal X-ray diffraction. Comparison with the structure of Nitron indicates that the formation of the thiones is accompanied by a shortening of the C-N bond within the 5-membered ring that is opposite to the thione group, and a lengthening of the exocyclic C-N bond. Analysis of the structures of Nitron, Nitron(S) and Nitron(S)(Me), together with hypothetical versions in which the phenyl substituents are replaced by hydrogen, indicates that these changes are in accord with bond order differences predicted by natural bond orbital methods. A similar evaluation of the thione groups of Nitron(S) and Nitron(S)(Me) indicates that the C-S bonds are composed of both covalent and ionic components and are best described by a combination of resonance structures that feature C=S double and C-S single bonds. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The molecular structures of two 1,2,4-triazole thiones derived from Nitron have been determined by single crystal X-ray diffraction, showing changes in bond lengths related to the formation of thiones. Analysis based on natural bond orbital methods predicted bond order differences and resonance structures for the thione groups.