Synthesis, Structural Characterization, Reactivity, and Catalytic Properties of Copper(I) Complexes with a Series of Tetradentate Tripodal Tris(pyrazolylmethyl)amine Ligands

Novel tris­(pyrazolylmethyl)­amine ligands TpaMe3, Tpa*,Br, and TpaBr3 have been synthesized and structurally characterized. The coordination chemistries of these three new tetradentate tripodal ligands and the already known Tpa and Tpa* have been explored using different copper­(I) salts as starting materials. Cationic copper­(I) complexes [TpaxCu]­PF6 (1–4) have been isolated from the reaction of [Cu­(NCMe)4]­PF6 and 1 equiv of the ligand. Complexes 2 (Tpax = Tpa*) and 3 (Tpax = TpaMe3) have been characterized by X-ray studies. The former is a 1D helical coordination polymer, and the latter is a tetranuclear helicate. In both structures, the Tpax ligand adopts a μ2:κ2:κ1-coordination mode. However, in solution, all of the four complexes form fluxional species. When CuI is used as the copper­(I) source, neutral compounds 5–8 have been obtained. Complexes 6–8 exhibit a 1:1 metal-to-ligand ratio, whereas 5 presents 2:1 stoichiometry. Its solid-state structure has been determined by X-ray diffraction, revealing its 3D polymeric nature. The polymer is composed by the assembly of [Tpa2Cu4I4] units, in which Cu4I4 presents a step-stair structure. The Tpa ligands bridge the Cu4I4 clusters, adopting also a μ2:κ2:κ1-coordination mode. As observed for the cationic derivatives, the NMR spectra of 5–8 show the equivalence of the three pyrazolyl arms of the ligands in these complexes. The reactivities of cationic copper­(I) derivatives 1–4 with PPh3 and CO have been explored. In all cases, 1:1 adducts [TpaxCuL]­PF6 [L = PPh3 (9–11), CO (12–15)] have been isolated. The crystal structure of [Tpa*Cu­(PPh3)]­PF6 (9) has been obtained, showing that the coordination geometry around copper­(I) is trigonal-pyramidal with the apical position occupied by the tertiary amine N atom. The Tpa* ligand binds the Cu center to three of its four N atoms, with one pyrazolyl arm remaining uncoordinated. In solution, the carbonyl adducts 13–15 exist as a mixture of two isomers; the four- and five-coordinate species can be distinguished by means of their IR νCO stretching bands. Finally, the catalytic activities of complexes 1–4 have been demonstrated in carbene- and nitrene-transfer reactions.已合成并完成结构表征的新型三(吡唑基甲基)胺配体包括TpaMe3、Tpa*,Br与TpaBr3。本研究以不同铜(I)盐为起始原料，探究了上述三种新型四齿三脚架型配体，以及已报道的Tpa与Tpa*的配位化学。通过[Cu(NCMe)4]PF6与1当量配体的反应，分离得到阳离子型铜(I)配合物[TpaxCu]PF6（编号1至4）。其中配合物2（Tpax=Tpa*）与3（Tpax=TpaMe3）已通过X射线衍射研究完成表征：前者为一维螺旋配位聚合物，后者为四核螺旋体。在两种配合物的晶体结构中，配体Tpax均采取μ2:κ2:κ1的配位模式。然而在溶液中，上述四种配合物均呈现流变物种。当以碘化亚铜（CuI）作为铜(I)源时，可得到中性化合物5至8。配合物6至8的金属与配体计量比为1:1，而配合物5的计量比为2:1。通过X射线衍射测定了配合物5的固态结构，结果显示其为三维聚合物，由[Tpa2Cu4I4]单元组装而成，其中Cu4I4簇呈现阶梯状结构。Tpa配体作为桥联配体连接Cu4I4簇，同样采取μ2:κ2:κ1的配位模式。与阳离子衍生物一致，配合物5至8的核磁共振波谱显示，其配体的三个吡唑基臂在溶液中等价。本研究还探究了阳离子型铜(I)衍生物1至4与三苯基膦（PPh3）及一氧化碳（CO）的反应性。所有反应均分离得到1:1加合物[TpaxCuL]PF6，其中L为PPh3（编号9至11）或CO（编号12至15）。已获得配合物[Tpa*Cu(PPh3)]PF6（9）的晶体结构，结果表明铜(I)的配位几何为三角锥形，顶点位置由叔胺氮原子占据。Tpa*配体与铜中心通过四个氮原子中的三个进行配位，剩余一个吡唑基臂未参与配位。在溶液中，羰基加合物13至15以两种异构体的混合物形式存在，可通过红外光谱中的νCO伸缩振动带区分四配位与五配位物种。最后，证实了配合物1至4在卡宾转移与氮宾转移反应中具备催化活性。