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The synthesis of a series of palladium(II) complexes of unsymmetrical, hybrid selenoether and telluroether ligands is reported. While the reaction of Pd(II) precursors with symmetrical telluroether ligands containing two coordinating groups results in cleavage of Te–C bond, no such labilisation is observed using unsymmetrical ligands containing one coordinating group. Two novel unsymmetrical selenoether ligands namely, N,N -dimethyl-2-(o -tolylselanyl)aniline (10) and 2-((2,6-dimethylphenyl)selanyl)- N,N -dimethylaniline (11) were synthesized from N,N -dimethylbenzylamine via the ortho -lithiation route. When ligands 10 and 11 were treated with Pd(COD)Cl 2 (COD = 1,5-cyclooctadiene), the reaction afforded novel Pd(II) complexes of the form Pd(2-NMe 2 CH 2 C 6 H 4)(R)SeCl 2 , where R = 2-MeC 6 H 4 (16) and 2,6-MeC 6 H 3 (17) respectively. Similarly, when unsymmetrical telluroether ligands, N,N -dimethyl-2-(phenyltellanyl)aniline (12) , N,N -dimethyl-2-(o-tolyltellanyl)aniline (13), 2-((2,6-dimethylphenyl)tellanyl)- N,N -dimethylaniline (14) and 2-((2,6-diisopropylphenyl)tellanyl)- N,N -dimethylaniline (15), which contain one coordinating group with an sp 3 N-donor atom, were treated with Pd(COD)Cl 2 , the palladium telluroether complexes of the form Pd(2-NMe 2 CH 2 C 6 H 4)(R)TeCl 2 , where R = C 6 H 5 (18), 2-MeC 6 H 4 (19), 2,6-MeC 6 H 3 (20) and 2,6- i PrC 6 H 3 (21) respectively were obtained. The selenoether complexes 16 and 17 and telluroether complexes 18 , 20 and 21 were characterized by single crystal X-ray diffraction studies. In the asymmetric unit of complex 18 , two molecules are present and due to the presence of weak, intermolecular Te⋯Cl interactions, the two molecules exist as symmetrically related dimer. The N-donor substituents, which were involved in intramolecular chalcogen bonding (IChB) with the chalcogen atoms in the free ligand, made six-membered chelating rings in the complexes. Again, when bis(2-phenylazophenyl- C,N ′)selenide 22 was treated with Pd(COD)Cl 2 , it afforded ortho C–H bond activated cyclopalladated complex 24. However, when bis(2-phenylazophenyl- C,N ′)telluride 23 was treated with Pd(COD)Cl 2 , due to strong IChB from two N-donor substituents, the reaction afforded cleaved product, [2-(phenylazo)phenyl-C,N′]tellurenyl chloride, 25. All the metal complexes exhibited significant downfield chemical shifts in 77Se/125Te NMR spectra as compared to the corresponding free ligands. The downfield shifts in the 77Se/125Te NMR signal in the complexes might be attributed to the coordination of the chalcogen atoms to the electropositive Pd(II) center. [ABSTRACT FROM AUTHOR]

The synthesis of a novel telluroxane cluster, [(R 2 TeO)(μ -TeO 2)(OTeR 2)][TeO(OH) 2 ] (R=C 6 H 5 NNC 6 H 4) is achieved by the oxidation of bis[2-(phenylazo)-phenyl- C,N ́] telluride with NaIO 4. The X-ray crystallographic diffraction studies in corroboration with Density Functional Theory calculation reveal that the cluster is stabilized by intramolecular Te···N and intra- and intermolecular O∙∙∙Te secondary bonding interactions. [Display omitted] The oxidation reaction of diorganotelluride R 2 Te, 1 (where R = C 6 H 5 NNC 6 H 4) with NaIO 4 resulted in the isolation of a telluroxane cluster, namely [(R 2 TeO)(μ -TeO 2)(OTeR 2)][TeO(OH) 2 ], 2. The formation of 2 was confirmed by multinuclear (1H, 13C and 125Te) NMR and FT-IR spectroscopy, and elemental analysis. The structure of compound 2 was further corroborated by X-ray crystallographic studies. It is observed that telluroxane cluster 2 was stabilized by intramolecular Te···N and intra- and intermolecular O∙∙∙Te secondary bonding interactions. The detailed electronic structural properties of the cluster were thoroughly investigated by Density Functional Theory (DFT) calculations. In particular, the hybridization of the Te atoms were calculated by Natural Bonding Orbital (NBO) analysis. The natural charges accumulated on the Te and the O atoms in compound 2 were calculated by Natural Population Analysis (NPA). In addition, the HOMO-LUMO energy gap in 2 was calculated. [ABSTRACT FROM AUTHOR]