Sadekov, I.D.; Minkin, V.I.; Zakharov, A.V.; Starikov, A.G.; Borodkin, G.S.; Aldoshin, S.M.; Tkachev, V.V.; Shilov, G.V. and Berry, Frank
Synthesis and structure of N-arylimines of beta-tellurocyclohexenals with the intramolecular coordination N -> Te bonds.
Journal of Organometallic Chemistry, 690(1) pp. 103–116.
A series of N-arylimines of beta-tellurocyclohexenals 11 have been synthesized and the molecular and crystal structures of the compounds 11a-e and also beta-(dimethyltelluronium)cyclohexenal perchlorate 12 studied by X-ray crystallography. All the compounds contain strong intramolecular coordination N --> Te (O --> Te) bonds of the hypervalent type. In 11a-e, the lengths of the N --> Te bonds are within the range of 2.690-2.147 Angstrom and are 1.0-1.5 Angstrom shorter than the sum of the van der Waals radii of respective atoms. In the N-arylimines 11a-e with the electronegative groups attached to the tellurium center, the lengths of the N --> Te bonds are very close to that characteristic of a standard covalent N-Te bond. The experimental observed geometries are well reproduced by the DFT calculations performed at B3LYP/LanL2DZ level of approximation. The energies of the intramolecular coordination N --> Te bonds vary from 23 kJ mol(-1) for 11a to 119 kJ mol(-1) for 11e. The calculated energy of the O --> Te bond in 12 was found to be 50 kJ mol(-1). The Te-125 NMR chemical shifts of compounds 11 span the wide range of 734.3-1622.4 ppm. The largest downfield Te-125 NMR chemical shifts are observed in the case of the compounds 11e, f in which the most electronegative atoms are attached to the tellurim centers.
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