1-Naphthyl- and mesityltellurium(IV, II) derivatives of small bite chelating organic ligands: Effect of steric bulk and intramolecular secondary bonding interaction on molecular geometry and supramolecular association

Abstract

The synthesis and characterization of unsymmetric diorganotellurium compounds containing a sterically demanding 1-naphthyl or mesityl ligand and a small bite chelating organic ligand capable of 1,4-Te⋯N(O) intramolecular interaction is described. The reaction of ArTeCl 3 (Ar = 1-C 10H 7, Np; 2,4,6-Me 3C 6H 2, Mes) with (SB)HgCl [SB = the Schiff base, 2-(4,4′-NO 2C 6H 4CH NC 6H 3-Me)] or a methyl ketone (RCOCH 3) afforded the corresponding dichlorides (SB)ArTeCl 2 (Ar = Np, 1Aa; Mes, 1Ba) or (RCOCH 2)ArTeCl 2 (Ar = Np; R = Ph ( 2Aa), Me ( 3Aa), Np ( 4Aa); Ar = Mes, R = Ph ( 2Ba)). Reduction of 1Aa and 1Ba by Na 2S 2O 5 readily gave the tellurides (SB)ArTe (Ar = Np ( 1A), Mes, ( 1B)) but that of dichlorides derived from methylketones was complicated due to partial decomposition to tellurium powder and diarylditelluride (Ar 2Te 2), resulting in poor yields of the corresponding tellurides 2A, 2B and 3A. Oxidation of the isolated tellurides with SO 2Cl 2, Br 2 and I 2 yielded the corresponding dihalides. All the synthesized compounds have been characterized with the help of IR, 1H, 13C, and 125Te NMR and in the case of 2Aa, and 2Ba by X-ray crystallography. Appearance of only one 125Te signal indicated that the unsymmetric derivatives were stable to disproportionation to symmetric species. Intramolecular 1,4-Te⋯O secondary bonding interactions (SBIs) are exhibited in the crystal structures of both the tellurium(IV) dichlorides, 2Aa, and 2Ba. Steric repulsion of the mesityl group in the latter dominates over lone pair–bond pair repulsion, resulting in significant widening of the equatorial C–Te–C angle. This appears to be responsible for the lack of Te⋯Cl involved supramolecular associations in the crystal structure of 2Ba.