Intramolecular O Te and N Te coordination bonds in molecules of -tellurocyclohexenals and their nitrogen analogs

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The structures of β-tellurocyclohexenals and their nitrogen analogs, viz., β-methyltellurocyclohexenal (6), β-(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), β-(4-ethoxyphenyltelluro)cyclohexenylidene(4"-methylaniline) (9), β-bromotellurenylcyclohexenylidene(4"-methylaniline) (10), and β-bromotellurenylcyclohexenal (4-methylbenzoyl)hydrazone (11), were studied by X-ray diffraction analysis. Compounds 6—11 have a Z configuration at the double bond, which provides the formation of intramolecular O→Te or N→Te coordination bonds. The bonds about the Te atom have a T-shaped configuration. There is only one of two possible O→Te coordination bonds in dialdehyde 8 and, consequently, this compound belongs to the 10-Te-3-tellurane structural type. Hydrazone 11 possesses both N→Te and O→Te intramolecular coordination bonds. Taking into account these interactions, the coordination polyhedron of the tellurium atom can be considered as a trigonal bipyramid. The intramolecular O→Te or N→Te coordination bond lengths in compounds 6 (2.692 A), 7 (2.657 A), 8 (2.657 A), and 9 (2.690 A) are 0.9—1.0 A smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 A) and 11 (2.203 A) are almost equal to the standard covalent bond length.