Isolation and structural characterization of some aryltellurium halides and their hydrolyzed products stabilized by an intramolecular Te···N interaction

Abstract

The isolation of pure [2-(phenylazo)phenyl-C,N']tellurium(IV) tribromide (6) has been achieved by modifying the reported procedure, which involved transmetalation of [2-(phenylazo)phenyl-C,N']mercury(II) chloride (7) with TeBr₄. The mixed-valent derivative bis[2-(phenylazo)phenyl-C,N']ditellurium dichloride (19), incorporating both a divalent and a tetravalent tellurium, was obtained serendipitously during the reduction of [2-(phenylazo)phenyl-C,N']tellurium(IV) trichloride (16) with hydrazine hydrate. Bis[2-(phenylazo)phenyl-C,N']telluride (10) has been synthesized by the ortho-lithiation route. Telluride 10, on treatment with SO₂Cl₂ and Br₂, underwent oxidative addition to give the expected Te(IV) halogenated products bis[2-(phenylazo)phenyl-C,N']tellurium(IV) dichloride (13) and bis[2-(phenylazo)phenyl-C,N']tellurium(IV) dibromide (11), respectively. However, a similar reaction of 10 with I₂ resulted in the formation of an unexpected telluronium cation, iodobis[2-(phenylazo)phenyl-C,N']telluronium triiodide (14), and [2-(phenylazo)phenyl-C,N']tellurenenyl(II) iodide (12). Alkaline hydrolysis of 16 under reflux conditions resulted in the formation of monomeric [2-(phenylazo)phenyl-C,N']tellurinic acid (20) and its sodium salt (21) as a cocrystal. Bis[[2-(phenylazo)phenyl-C,N']tellurium]oxide (22) was obtained from the hydrolysis of [2-(phenylazo)phenyl-C,N']tellurium(II) chloride (17). The reaction of 13 with an alkaline solution resulted in the formation of the corresponding bis[2-(phenylazo)phenyl-C,N']tellurium(IV) oxide (23) and dichlorobis[2-(phenylazo)phenyl-C,N']tellurium(IV) oxide (24). The identity of all the derivatives was confirmed by multinuclear NMR (¹H, ¹³C, ¹²⁵Te) and FT-IR spectroscopy, elemental analysis, and ESI-MS. The structures for tellurium derivatives 6, 10-14, 17, 19, 20-23, and 23A were also confirmed by X-ray crystallography. Density functional theory (DFT) was utilized for optimizing the geometries of 11, 13, and 14 to examine the possibility of a four-membered intramolecular Te···N interaction.