Synthesis and characterization of a family of systematically varied tris(2-pyridyl)methoxymethane ligands: Copper(I) and copper(II) complexes
Synthesis and characterization of a family of systematically varied tris(2-pyridyl)methoxymethane ligands: Copper(I) and copper(II) complexes
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DOI：
10.1021/ic9713487
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发表时间：
1998-12-28
影响因子：
4.6
通讯作者：
Stack, TDP
中科院分区：
文献类型：
--
作者：
Jonas, RT;Stack, TDP
基于三（2-吡啶基）甲氧基甲烷骨架，开发了一种高效的模块化方案，用于合成一系列面盖三吡啶基配体，该方案允许配体外围空间需求的系统变化。本文介绍了一类以Cu(I)和Cu（II）为外围位置的0—>3甲氧基配体的配位化学。配体为三（2-吡啶基）甲氧基甲烷（LO）、二（2-吡啶基）（2-（6-甲氧基）吡啶基）甲氧基甲烷（L-1）、二（2-（6-甲氧基）吡啶基）甲氧基甲烷（L-2）和三（2-（6-甲氧基）吡啶基）甲氧基甲烷（L-3）。配体交换行为，在较小程度上，这些配合物的结构在引入甲氧基取代基的小扰动下变化很大。Cu(I)配合物在溶液和固体中有两种不同的配位模式。一种是由面盖三吡啶配体和单齿配体如CH3CN、CO或PPh3组成的伪四面体配体。另一种结构类型也是由两个三吡啶配体以双齿方式配位形成的假四面体Cu(I)单体，与非甲氧基吡啶亚基结合较好。除了最具位阻性的配体L-3只对Cu(I)单键化外，所有配体都能形成两种类型的Cu(I)配合物，其形成受化学计量控制。竞争配体结合实验和CO(g)取代实验表明，[(L-0)(2)Cu]（+）和[(L-1)(2)Cu]（+）配合物在非质子溶剂中具有几乎相等的稳定性，并且由于在Cu(I)配位球中包裹了大体积的甲氧基吡啶，因此比[(L-2)(2)Cu]（+）配合物具有更大的稳定性。配体系列中的Cu（II）配合物生成“双-三”[(L0—>3)(2)Cu]（2+）配合物，Cu（II）在四方畸变的八面体配位环境中结合。配体外围的体积大小决定了Cu(II)-配体在溶液和固体状态下的键长。在这些配合物中，庞大的吡啶环倾向于在轴向位置结合。对于空间负担最严重的配体L-3，二配态Cu（II）配合物对水分敏感，反应生成单聚的三水化合物[(LCu)-Cu-3(H2O)(3)]（2+）。
An efficient modular protocol for synthesizing a series of facial-capping tris-pyridyl ligands, based on the tris(2-pyridyl)methoxymethane backbone, has been developed which allows for systematic variations of the steric demands at the periphery of the ligand. The coordination chemistry of one such family of ligands that positions 0-->3 methoxy groups at the periphery with Cu(I) and Cu(II) is presented. The Ligands are tris(2-pyridyl)methoxymethane (LO), bis(2-pyridyl)(2-(6-methoxy)pyridyl)methoxymethane (L-1), bis(2-(6-methoxy)pyridyl)(2-pyridyl)-methoxymethane (L-2), and tris(2-(6-methoxy)pyridyl)methoxymethane (L-3). The ligand exchange behavior and, to a lesser extent, the structures of the these complexes vary dramatically given the small perturbation of introducing methoxy substituents. Two distinct coordination modes are observed for the Cu(I) complexes, both in solution and the solid state. One is a pseudo-tetrahedral coordination comprised of the facial-capping, trispyridyl ligand and a monodentate ligand such as CH3CN, CO, or PPh3. The other structural type is also a pseudotetrahedral Cu(I) monomer formed by two tris-pyridyl ligands coordinated in a bidentate manner with preferable binding by the nonmethoxy pyridyl subunits. With the exception of the most sterically hindered ligand, L-3, which only displays monoligation to Cu(I), all ligands form both types of Cu(I) complexes, and the formation is controlled by stoichiometry. Both competitive ligand binding experiments and ligand substitution with CO(g) show that the [(L-0)(2)Cu](+) and [(L-1)(2)Cu](+) complexes have nearly equivalent stability in aprotic solvent, and greater stability than the [(L-2)(2)Cu](+) complex due to inclusion of bulky methoxypyridines into the Cu(I) coordination sphere. The Cu(II) complexes of the ligand series generate "bis-tris", [(L0-->3)(2)Cu](2+) complexes, with the Cu(II) ligated in a tetragonally distorted octahedral coordination environment. The degree of bulk at the ligand periphery dictates the Cu(II)-ligand bond lengths both in solution and the solid state. In-these complexes, the bulky pyridyl ring prefers to bind in the axial position. For the most sterically encumbered ligand, L-3, the bisligated Cu(II) complex is moisture sensitive, reacting to give a monoligated, tris-aqua species, [(LCu)-Cu-3(H2O)(3)](2+).