Structure and magnetic properties of novel heteroheptanuclear metal string complex [Ni3Ru2Ni2(μ7-teptra)4(NCS)2](PF6)

We report the synthesis of a novel heteroheptanuclear metal string complex (HMSC) [Ni3Ru2Ni2(μ7-teptra)4(NCS)2](PF6) 1 supported by tetra-pyridyl-tri-amine (H3teptra) ligands. We employed X-ray diffraction and other spectroscopic techniques to characterize the complex. The observed remarkably short Ru–Ru distances of 2.2499(3) A for 1 is indicative of a unique metal-metal interaction in the mixed-valence [Ru2]5+ (S = 3/2) unit. The complex exhibits relatively high magnetic moment values of 4.55 B.M. at 4 K, increases rapidly to 6.00 B.M. at 30 K, and remains at 6.11 B.M. from 50 – 300 K in SQUID measurements indicating a high spin (S ≥ 3/2) system which is further supported in the analyses of EPR spectra at low temperatures. These magnetic behaviors can be ascribed to a result of spin-exchange interactions among multi-spin centers.