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 [Cu 3 (DPhIP) 2 ](CuCl 2 ) ( 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 CuCl 2 - anions, and each anion interacts with two neighboring [Cu 3 (DPhIP) 2 ] + cations forming an infinite zigzag chain of Cu I atoms. Also reported here is the linear tetracopper chain cation in [Cu 4 (DPhIP) 4 ][CuCl 2 ] 2 ( 2 ). The [Cu 4 (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 Cu I while the two inner Cu atoms are 4-coordinate Cu II . 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.