Trimetallic [M 3 (dpa) 4 ] 2+ Complexes (M = Co, Ni) as Building Blocks for Cyano‐Bridged Coordination Polymers

Reactions between the complexes M 3 (dpa) 4 Cl 2 (M = Co, Ni; dpa = 2,2′‐dipyridylamine), which contain linear trimetallic fragments, and (Bu 4 N) 3 [M′(CN) 6 ] (M′ = Fe, Co) result in the formation of CN‐bridged coordination polymers. The analysis of the products obtained suggests that they have a two‐dimensional structure, in which ditopic [M 3 (dpa) 4 ] 2+ linkers bridge 4‐connected [M′(CN) 6 ] 3– nodes into an extended layer. The synthesis of {[Co 3 (dpa) 4 ] 1.97 [Fe(CN) 6 ]}Cl 0.8 ( 1 ) is accompanied by an electron transfer from the tricobalt to the hexacyanoferrate units, which results in the formation of [Co 3 (dpa) 4 ] 3+ and [Fe(CN) 6 ] 4– fragments. In {[Ni 3 (dpa) 4 ] 1.74 [Fe(CN) 6 ]}Cl 0.45 ( 3 ), a partial charge transfer between the trinickel and the hexacyanoferrate units leads to the temperature‐dependent Fe III /Fe II mixed valence, and lower temperatures favor the thermodynamic Fe III ground state. {[Co 3 (dpa) 4 ] 2.06 [Co(CN) 6 ]}Cl 1.1 ( 2 ) exhibits spin‐glass behavior with a spin‐freezing point of approximately 4.8 K, which is due to the magnetic superexchange between the paramagnetic [Co 3 (dpa) 4 ] 2+ ( S = 1/2) units through the diamagnetic [Co(CN) 6 ] 3– linkers.