An Infinite Zigzag Chain and the First Linear Chain of Four Copper Atoms; Still No Copper−Copper Bonding

We have prepared and characterized ionic compounds containing linear or zigzag chains of copper ions. For
[Cu3(DPhIP)2](CuCl2) (1), in addition to the well-known [ClCuCl]- anion, there is a cation with a linear chain
of three Cu atoms bridged by two DPhIP anionic ligands (DPhIP represents the anion of 2,6-diphenyliminopiperidine). Each cation has weak interactions with two adjacent CuCl2- anions, and each anion interacts with two
neighboring [Cu3(DPhIP)2]+ cations forming an infinite zigzag chain of CuI atoms. Also reported here is the
linear tetracopper chain cation in [Cu4(DPhIP)4][CuCl2]2 (2). The [Cu4(DPhIP)4]2+ cation has approximate D2d
symmetry. There are three Cu···Cu distances of 2.518(2), 2.479(2), and 2.525(2) Å. The terminal Cu atoms are
2-coordinate CuI while the two inner Cu atoms are 4-coordinate CuII. In spite of the diamagnetic nature of this
compound, molecular orbital calculations (by various DFT techniques) indicate that no direct Cu−Cu bonds are
present; instead the bridging ligand effects a strong coupling of the spins.

本研究制备并表征了一系列含有铜离子直链或锯齿链结构的离子化合物。针对配合物[Cu₃(DPhIP)₂](CuCl₂) (1)，除了已知的[ClCuCl]⁻阴离子外，还存在由两个DPhIP阴离子配体桥联的三铜原子直链阳离子（其中DPhIP代表2,6-二苯基亚氨基哌啶的阴离子形式）。每个阳离子与相邻的两个[CuCl₂]⁻阴离子存在弱相互作用，而每个阴离子则与邻近的两个[Cu₃(DPhIP)₂]⁺阳离子相互作用，进而形成无限延伸的一价铜（CuI）锯齿链结构。本研究同时报道了配合物[Cu₄(DPhIP)₄][CuCl₂]₂ (2)中的线性四铜链阳离子。[Cu₄(DPhIP)₄]²⁺阳离子具有近似D₂d点群对称性，其Cu···Cu间距分别为2.518(2)、2.479(2)和2.525(2) Å。其中，末端铜原子为二配位的一价铜（CuI），内部两个铜原子为四配位的二价铜（CuII）。尽管该化合物呈现抗磁性，但多种密度泛函理论（Density Functional Theory, DFT）的分子轨道计算结果表明，体系中不存在直接的Cu−Cu键；相反，桥联配体实现了自旋间的强耦合作用。