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

The bis[hydrotris(1,2,4‐triazolyl)borate]metal complexes [M{HB(C 2 H 2 N 3 ) 3 } 2 ] with M = Fe ( 5 ), Co ( 6 ), Cu ( 7 ), Zn ( 8 ) are obtained from MX 2 and K[HB(C 2 H 2 N 3 ) 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 CH 3 OH and 9 · 2 H 2 O have been determined. The structure of 7 · 4 CH 3 OH 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 CH 3 OH is monoclinic, space group P 2 1 / n. Compound 9 · 2 H 2 O 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 Ccm 2 1 .