The first crystal structures of six- and seven-membered tellurium- and nitrogen-containing (Te—N) heterocycles: 2H-1,4-benzotellurazin-3(4H)-one and 2,3-dihydro-1,5-benzotellurazepin-4(5H)-one

Abstract

There is a paucity of data concerning the structures of six- and seven-membered tellurium- and nitrogen-containing (Te—N) heterocycles. The title compounds, C8H7NOTe, (I), and C9H9NOTe, (II), represent the first structurally characterized members of their respective classes. Both crystallize with two independent molecules in the asymmetric unit. When compared to their sulfur analogs, they exhibit slightly greater deviations from planarity to accommodate the larger chalcogenide atom, with (II) adopting a pronounced twist-boat conformation. The C—Te—C angles of 85.49 (15) and 85.89 (15)° for the two independent molecules of (I) were found to be somewhat smaller than those of 97.4 (2) and 97.77 (19)° for the two independent molecules of (II). The C—Te bond lengths [2.109 (4)–2.158 (5) Å] are in good agreement with those predicted by the covalent radii. Intermolecular N—H...O hydrogen bonding in (I) forms centrosymmetricR22(8) dimers, while that in (II) forms chains. In addition, intermolecular Te...O contacts [3.159 (3)–3.200 (3) Å] exist in (I).