Binary [Hydrotris(1,2,4‐triazolyl)borate]metal Complexes [M{HB(C2H2N3)3}2] with M = Fe, Co, Cu, Zn: Synthesis, Characterization, Magnetochemistry, and X‐ray Structure of [Cu{HB(C2H2N3)3}2·4CH3

The bis[hydrotris(1,2,4‐triazolyl)borate]metal complexes [M{HB(C2H2N3)3}2] with M = Fe (5), Co (6), Cu (7), Zn (8) are obtained from MX2 and K[HB(C2H2N3)3] (9). The complexes are characterized by IR, UV/Vis, and MS. Temperature‐variable magnetic measurements show a Curie‐Weiss behavior for the paramagnetic complexes 6 and 7 with a temperature‐dependent magnetic moment for 6. The iron complex 5 exhibits a spin crossover from diamagnetic to paramagnetic, starting at around 270 K. Single‐crystal X‐ray structures of the solvates 7 · 4 CH3OH and 9 · 2 H2O have been determined. The structure of 7 · 4 CH3OH shows the Jahn‐Teller distorted copper complex 7 surrounded by methanol molecules through hydrogen bonding to exocyclic nitrogen atoms of the tris(1,2,4‐triazolyl)borate ligand. The crystal system for 7 · 4 CH3OH is monoclinic, space group P21/n. Compound 9 · 2 H2O is a one‐dimensional coordination polymer with the potassium atom bridged by the water molecules and the tris(1,2,4‐triazolyl)borate ligand and crystallizes in the orthorhombic space group Ccm21.