Department of Chemistry, University of Lucknow, Lucknow, 226007, India.
Dalton Trans. 2010 Mar 14;39(10):2637-43. doi: 10.1039/b921362g. Epub 2010 Feb 3.
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 alpha-bromoacetamides and provides a direct synthetic route to the stable, crystalline amidomethyltellurium(IV) dibromides, (RR'NCOCH(2))(2)TeBr(2) (RR'N = Et(2)N (1b), MePhN (2b), Me(c-Hex)N (3b), O(CH(2)CH(2))(2)N (4b)) and (Et(2)NCOCH(2))ArTeBr(2) (Ar = mesityl, 5b; 1-naphthyl, 6b). Biphasic bisulfite reduction of the dialkyltellurium dibromides afforded yellow to orange coloured amido functionalized symmetrical telluroethers, (RR'NCOCH(2))(2)Te (RR'N = Et(2)N (1), MePhN (2), Me(c-Hex)N (3), O(CH(2)CH(2))(2)N (4)), of which compound 2 was isolated as a crystalline solid. Oxidation of the new dialkyltelluroethers with dihalogens (Br(2), I(2)) or SO(2)Cl(2) afforded the corresponding amidomethyltellurium(IV) dihalides, (RR'NCOCH(2))(2)TeX(2) (RR'N = Et(2)N, 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(CH(2)CH(2))(2)N, X = Cl (4a), Br (4b), I (4c)) that were characterized by elemental analyses and multinuclear ((1)H, (13)C, (125)Te) 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.
在温和条件下，Te(0)（元素碲）和 Te(II)（芳基碲溴化物，原位）的氨甲基化反应很容易进行。它涉及低价碲的氧化插入 N-取代的α-溴乙酰胺的 C-Br 键中，并提供了一种直接的合成方法，可得到稳定的、结晶的氨甲基碲(IV)二溴化物，(RR'NCOCH(2))(2)TeBr(2)（RR'N = Et(2)N(1b)、MePhN(2b)、Me(c-Hex)N(3b)、O(CH(2)CH(2))(2)N(4b)）和（Et(2)NCOCH(2))ArTeBr(2)（Ar = 均三甲苯，5b；1-萘基，6b）。二烷基碲二溴化物的两相亚硫酸氢盐还原得到黄色至橙色的氨官能化对称碲醚，(RR'NCOCH(2))(2)Te（RR'N = Et(2)N(1)、MePhN(2)、Me(c-Hex)N(3)、O(CH(2)CH(2))(2)N(4)），其中化合物 2 被分离为结晶固体。新的二烷基碲醚用二卤化物（Br(2)、I(2)）或 SO(2)Cl(2)氧化得到相应的氨甲基碲(IV)二卤化物，(RR'NCOCH(2))(2)TeX(2)（RR'N = Et(2)N，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(CH(2)CH(2))(2)N，X = Cl(4a)、Br(4b)、I(4c)），这些化合物通过元素分析和多核（1H、13C、125Te）NMR 进行了表征。1b、1c、2、2b、2c、4b、5b 和 6b 的单晶 X 射线数据表明，N-取代的氨甲基基团通过分子内 1,4-Te...O 配位充当小位螯合配体，朝向 Te(IV)中心。由于分子内次级键相互作用，Te(IV)周围的空间位阻、Te(II)的低电正性以及由于酰胺基团的共振特征导致的 N 上的部分正电荷，可能阻止这些原子参与固态中的分子间缔合力。相反，弱的 C-H...O 和 C-H...X H-键合相互作用在自组装中占据中心位置。
