Syntheses, Structures, and Magnetic Properties of Unusual Nonlinear Polynuclear Copper(II) Complexes Containing Derivatives of 1,2,4-Triazole and Pivalate Ligands

Novel polynuclear Cu(II) complexes containing derivatives of 1,2,4-trizaole and pivalate ligands, [Cu3(μ3-OH)(μ-adetrz)2(piv)5(H2O)]·6.5H2O (1) (adetrz = 4-amino-3,5-diethyl-1,2,4-triazole, piv = pivalate), [Cu4(μ3-OH)2(μ-atrz)2(μ-piv)4(piv)2]·2MeOH·H2O (2) (atrz = 4-amino-1,2,4-triazole), [Cu4(μ3-OH)2(μ-tbtrz)2(μ-piv)2(piv)4]·4H2O (3) (tbtrz
= 4-tert-butyl-1,2,4-trizaole), and [Cu4(μ3-O)2(μ-admtrz)4(admtrz)2(μ-piv)2(piv)2]·2[Cu2(μ-H2O)(μ-admtrz)(piv)4]·13H2O
[4 = 4a·2(4b)·13H2O; admtrz = 4-amino-3,5-dimethyl-1,2,4-triazole], have been prepared and structurally
characterized. 1 is an asymmetrical triangular complex containing a [Cu3(μ3-OH)] core with two Cu---Cu edges
spanned by bridging adetrz ligands. 2, 3, and 4a are novel tetranuclear compounds containing a [Cu4(μ3-O)2] or
[Cu4(μ3-OH)2] core with Cu---Cu edges spanned by bridging 1,2,4-triazole or pivalate ligands. 4b is a dinuclear
compound with one admtrz and one water bridge, and it is the first dinuclear Cu(II) triazole complex with one
bridging water molecule. 1 is one of few reported triangular Cu(II) complexes with derivatives of 1,2,4-triazole,
while 2, 3, and 4a are the first group of the nonlinear tetranuclear Cu(II) compounds with derivatives of 1,2,4-triazole. Variable-temperature magnetic susceptibility studies on the powder samples of 1−3 reveal the overall
antiferromagnetic coupling between CuII ions with J values of −55.6 to −12.8 cm-1 (1), −216.4 to 0 cm-1 (2), and
−259.8 to 4.8 cm-1 (3).