Issue 10, 2010

Amidomethylation of elemental tellurium: Synthesis and solid state structures of N-substituted amidomethyltellurium(iv & ii) derivatives

Abstract

Amidomethylation of Te(0) (elemental tellurium) as well as Te(II) (aryltellurium bromide, in situ) proceeds readily under mild conditions. It involves oxidative insertion of low valent tellurium into the C–Br bond of N-substituted α-bromoacetamides and provides a direct synthetic route to the stable, crystalline amidomethyltellurium(IV) dibromides, (RR′NCOCH2)2TeBr2 (RR′N = Et2N (1b), MePhN (2b), Me(c-Hex)N (3b), O(CH2CH2)2N (4b)) and (Et2NCOCH2)ArTeBr2 (Ar = mesityl, 5b; 1-naphthyl, 6b). Biphasic bisulfite reduction of the dialkyltellurium dibromides afforded yellow to orange coloured amido functionalized symmetrical telluroethers, (RR′NCOCH2)2Te (RR′N = Et2N (1), MePhN (2), Me(c-Hex)N (3), O(CH2CH2)2N (4)), of which compound 2 was isolated as a crystalline solid. Oxidation of the new dialkyltelluroethers with dihalogens (Br2, I2) or SO2Cl2 afforded the corresponding amidomethyltellurium(IV) dihalides, (RR′NCOCH2)2TeX2 (RR′N = Et2N, X = Cl (1a), Br (1b), I (1c); RR′N = MePhN, X = Cl (2a), Br (2b), I (2c); RR′N = Me(c-Hex)N, X = Cl (3a), Br (3b), I (3c); RR′N = O(CH2CH2)2N, X = Cl (4a), Br (4b), I (4c)) that were characterized by elemental analyses and multinuclear (1H, 13C, 125Te) NMR. Single crystal X-ray data on 1b, 1c, 2, 2b, 2c, 4b, 5b and 6b suggest that the N-substituted amidomethyl group acts as a small-bite chelating ligand, via intramolecular 1,4-Te⋯O coordination, towards the Te(IV) centre. Steric congestion around Te(IV) due to intramolecular secondary bonding interaction(s), reduced electrophilicity of Te(II) and the partial positive charge on N due to the resonating character of the amido group presumably prevents these atoms from participating in the intermolecular associative forces in the solid state. Instead, weak C–H⋯O and C–H⋯X H-bonding interactions take centre-stage in the self assembly.

Graphical abstract: Amidomethylation of elemental tellurium: Synthesis and solid state structures of N-substituted amidomethyltellurium(iv & ii) derivatives

Supplementary files

Article information

Article type
Paper
Submitted
14 Oct 2009
Accepted
15 Dec 2009
First published
03 Feb 2010

Dalton Trans., 2010,39, 2637-2643

Amidomethylation of elemental tellurium: Synthesis and solid state structures of N-substituted amidomethyltellurium(IV & II) derivatives

S. Misra, A. K. S. Chauhan, P. Singh, R. C. Srivastava, A. Duthie and R. J. Butcher, Dalton Trans., 2010, 39, 2637 DOI: 10.1039/B921362G

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