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 D 2 d 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.