Design of base metal extractants. Part 1. Inter-ligand hydrogen bonding in the assembly of pseudo-macrocyclic bis(aminosulfonamidato)M(ii) complexes
作者:Clare Squires、Christopher W. Baxter、John Campbell、Leonard F. Lindoy、Hamish McNab、Andrew Parkin、Simon Parsons、Peter A. Tasker、Gang Wei、David J. White
DOI:10.1039/b515650p
日期:——
Monosulfonyl derivatives of simple 1,2- and 1,3-diamines (R2HN–R–NHSO2R1 = L) have been shown to be easily deprotonated to give neutral 2 : 1 complexes, [M(L
− H)2], with Co(II), Ni(II), Cu(II) or Zn(II). The Ni(II) and Cu(II) complexes with deprotonated N-tosyl-1,2-diaminoethane have a planar N42− donor set and a 14-membered pseudo-macrocyclic structure based on head-to-tail SO⋯H–N(amine) bonding between the two bidentate ligands. In the related tetrahedral Zn(II) complex the ends of the mutually perpendicular bidentate N2− units are too far apart to form a cyclic H-bonded system. X-Ray structure determinations on five free ligands provide evidence for extensive inter-molecular H-bonding, which in the case of N-tosyl-1,3-diaminopropane and its N′-tert-butyl derivative involves formation of dimeric 16-membered pseudo-macrocycles. Despite favourable inter-ligand H-bonding in the neutral 2 : 1 complexes, these ligands are relatively weak extractants, showing >50% loading of Cu(II) in “pH-swing” equilibria, 2 L(org)
+ M2+ = [M(L
− H)2](org)
+ 2 H+, only when the pH of the aqueous phase is raised above 4.
研究表明,简单的 1,2- 和 1,3- 二胺(R2HN-R-NHSO2R1 = L)的单磺酰衍生物很容易去质子化,从而与 Co(II)、Ni(II)、Cu(II) 或 Zn(II) 生成 2 : 1 的中性络合物 [M(L-H)2]。含有去质子化 N-对甲基苯磺酰-1,2-二氨基乙烷的 Ni(II) 和 Cu(II) 复合物具有平面 N42 供体组和 14 元伪大环结构,该结构基于两个双齿配体之间头对尾的 SO⋯H-N(胺)键。在相关的四面体 Zn(II) 复合物中,相互垂直的双齿 N2- 单元两端相距太远,无法形成环状 H 键体系。对五种游离配体的 X 射线结构测定证明了分子间广泛的 H 键作用,在 N-对甲苯磺酸-1,3-二氨基丙烷及其 N′-叔丁基衍生物中,这种作用涉及形成二聚 16 元伪大环。尽管在中性 2 : 1 复合物中存在有利的配体间氢键,但这些配体是相对较弱的萃取剂,只有当水相的 pH 值升高到 4 以上时,才会在 "pH 波动 "平衡(2 L(org) + M2+ = [M(L - H)2](org) + 2 H+)中显示出大于 50% 的 Cu(II) 负载。