Synthesis of intramolecularly coordinated heteroleptic diorganotellurides and diorganotelluroxides: Isolation of monomeric diorganotelluroxide [{2,6-(Me2NCH2)2C6H3}2TeO] and diorganohydroxytelluronium chloride [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl

Abstract

A series of heteroleptic diorganotellurides (2-NMe2CH2C6H4)(R)Te, where R = C6H5 (5), 2-MeC6H4 (6), 2,6-MeC6H3 (7) and 2,6-iPrC6H3 (8) was synthesised from N,N-dimethylbenzylamine via the ortho-lithiation route. Reactions of 5–8 with SO2Cl2 followed by alkaline hydrolysis afforded diorganotelluroxides (2-NMe2CH2C6H4)(R)TeO, where R = C6H5 (10), 2-MeC6H4 (11), 2,6-MeC6H3 (12) and 2,6-iPrC6H3 (13) respectively. A similar alkaline hydrolysis of homoleptic diorganotellurides, {2,6-(Me2NCH2)2C6H3}2Te (9), afforded a co-crystal of [{2,6-(Me2NCH2)2C6H3}2TeO] (14a) and disordered [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl (14b) or a completely ordered diorganohydroxytelluronium chloride [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl (14c). Heteroleptic diorganotellurides 7–8 and telluroxides 10–14a-b and diorganohydroxytelluronium chloride 14c were characterised by single crystal X-ray diffraction studies. In the molecular structures, the N-donor substituent made five membered chelating ring with the tellurium atom via Te⋯N secondary bonding interactions. Diorganotelluroxide 10 existed in dimeric form exhibiting both intramolecular Te⋯N and intermolecular Te⋯O secondary interactions. Due to the strong intramolecular Te⋯N secondary bonding interactions from the three N-donor substituents, diorganotelluroxide 14a was stabilised in the monomeric form. This is, in fact, the only second example of a discrete monomeric diorganotelluroxide. Again, because of the presence of intramolecular Te⋯N secondary bonding interactions, the diorganotelluroxides 10–14a-b and diorganohydroxytelluronium chloride 14c exhibited downfield 125Te NMR chemical shift as compared with the earlier reported oligomeric or polymeric diorganotelluroxides.