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

The structures of beta-tellurocyclohexenals and their nitrogen analogs, viz., beta-methyl-tellurocyclohexenal (6), beta-(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), beta-(4-ethoxyphenyltelluro)cyclohexenylidene(4'-methylaniline) (9), beta-bromotellurenylcyclohexenylidene(4'-methylaniline) (10), and beta-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 Angstrom), 7 (2.657 Angstrom), 8 (2.657 Angstrom), and 9 (2.690 Angstrom) are 0.9-1.0 Angstrom smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 Angstrom) and 11 (2.203 Angstrom) are almost equal to the standard covalent bond length.