Sterically Hindered Tellurium(IV) Catecholate as a Lewis Acid

Sterically hindered tellurium catecholate Te(Cat(36))(2) (Cat(36) = 3,6-di-tertbutyl-catecholate) was synthesized with the reaction of amorphous Te with 3,6-di-tertbutyl-o-benzoquinone. Adducts of Te(Cat(36))(2) with various O- and N-donors were isolated and characterized by means of single-crystal X-ray diffraction along with IR, UV-vis, and NMR (H-1, C-13, and Te-125) spectroscopies. In the crystal structure of the adduct with 2,2'-bipyridine (bipy), the unprecedented mu-kappa N-2,N':kappa N-2,N'-bridging coordination mode of bipy was observed. Various intermolecular interactions Te center dot center dot center dot O, Te center dot center dot center dot N, and Te center dot center dot center dot C in adducts were analyzed using density functional theory calculations and quantum theory of atoms in molecules analysis. The estimated strength for appropriate short contacts varies from 0.9 to 5.3 kcal/mol, and they are attractive and purely non-covalent.