Cyclic Trinuclear and Chain of Cyclic Trinuclear Copper(II) Complexes Containing a Pyramidal Cu₃O(H) Core. Crystal Structures and Magnetic Properties of [Cu₃(μ₃-OH)(aaat)₃(H₂O)₃](NO₃)₂·H₂O [aaat = 3-Acetylamino-5-amino-1,2,4-triazolate] and {[Cu₃(μ₃-OH)(aat)₃(μ₃-SO₄)]·6H₂O}_n [aat = 3-Acetylamino-1,2,4-triazolate]: New Cases of

Abstract

New copper(II) complexes of the cyclic trinuclear type with 1,2,4-triazole ligands, [Cu(3)(mu(3)-OH)(aaat)(3)(H(2)O)(3)](NO(3))(2).H(2)O [Haaat = 3-acetylamino-5-amino-1,2,4-triazole] (1) and ([Cu(3)(mu(3)-OH)(aat)(3)(mu(3)-SO(4))].6H(2)O)(n) [Haat = 3-acetylamino-1,2,4-triazole] (2), have been prepared and characterized by X-ray crystallography and magnetic measurements. Compound 1, the first reported with the ligand (H)aaat, consists of discrete trinuclear cations, associated NO(3)(-) anions and lattice water molecules. Compound 2 consists of unusual chains of trinuclear units with a tridentate sulfato group linking the trimeric units and water molecules stabilizing the crystal lattice. In both complexes, 1 and 2, the trinuclear [Cu(3)(OH)L(3)] unit contains a pyramidal Cu(3)-mu(3)OH core, and an almost flat Cu(3)N(6) ring formed by the N,N-bridging triazolato groups. The Cu...Cu' intratrimeric distances are 3.35-3.37-3.39 A in 1 and 3.34-3.34-3.36 A in 2. The copper atoms are five-coordinated with a distorted square-pyramidal geometry. Magnetic measurements have been performed in the 1.9-300 K temperature range. In the high-temperature region (T > 90 K), experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -J(S(1)S(2) + S(2)S(3) + S(1)S(3)), with J = -194.6 cm(-1) and g = 2.08 for 1, and J = -185.1 cm(-1) and g = 2.10 for 2. The magnitude of the antiferromagnetic exchange in both complexes is discussed on the basis of their structural features by comparison with reported N,N-pheripherically bridged trinuclear systems. In order to fit the experimental magnetic data at low temperature, an antisymmetric exchange term, H(AS) = G(S(1)xS(2) + S(2)xS(3) + S(1)xS(3)), had to be introduced, with G = 27.8 (1) and 31.0 (2) cm(-1). Crystal data: C(12)H(27)Cu(3)N(17)O(14) (1) (MW = 824.13) crystallizes in the triclinic space group, P(-)1, Z = 2, with the cell dimensions a = 8.852(2) A, b = 11.491(3) A, c = 15.404(3) A, alpha = 70.43(3) degrees, beta = 75.11(2) degrees, gamma = 88.43(2) degrees, and V = 1423.8(5) A(3), D(calcd) = 1.922 g cm(-)(3); the final agreement values were R1 = 0.0822 and wR2 = 0.2300 for 4989 unique reflections. C(12)H(28)Cu(3)N(12)O(14)S (2) (MW = 787.14) crystallizes in the triclinic space group, P(-)1, Z = 2, with the cell dimensions a = 7.146(6) A, b = 14.26(1) A, c = 15.35(2) A, alpha = 109.0(9) degrees, beta = 93.6(9) degrees, gamma = 99.5(7) degrees, and V = 1448(2) A(3), D(calcd) = 1.806 g cm(-3); the final agreement values were R1 = 0.0628 and wR2 = 0.1571 for 3997 "observed" reflections.

Ferromagnetic Properties of a Trinuclear Nickel(II) Complex with a Trithiocyanurate Bridge

“…[30,31] The second model accounts for antisymmetric exchange [Equation (5)]. (5) The symmetry rules reveal that only the z component of the parameter vector will apply so that we are left with a single antisymmetric exchange parameter d z . The net effect of the antisymmetric exchange is a kind of ZFS (different from that produced by the asymmetric exchange) and a marked drop in g x ϽϽ 2.…”

“…In the literature we can find examples of these trinuclear complexes where the copper centers are often bridged by hydroxy groups or nitrogen heterocycles. [4][5][6] If we have in mind trinuclear nickel(II) complexes, we can find in the literature linear ones, for example, linear trinuclear nickel(II) complex with thiocyanato and pyridazine bridges have been reported by Cano et al [7] [{Ni(dien)} 2 (µ-ox){µ-Ni(CN) 4 }] can serve as an example of a trinuclear complex with oxalato as well as cyano bridges, but from a magnetic point of view, the compound can be treated as a dimer. [8] More interesting are azido-bridged trinuclear triangular complexes [{Ni(tet)} 3 (µ-N 3 ) 3 ](PF 6 ) 3 and [{Ni(tet)} 3 (µ-N 3 ) 3 ](ClO 4 ) 3 , tet = triethylenetetraamine with antiferromagnetic exchange interactions.…”

Polymer complexes. LV. Spectroscopic, thermal studies, and coordination of metal ions N-[3-(5-amino-1,2,4-triazolo)] acrylamide polymer complexes

“…Thus, the smaller value of the wavelength of the band corresponding to the transition resembles a geometry of the complex between tetrahedral and square planar. Ferrer et al [37] reported copper(II) complexes derived from 1,2,4-triazole ligands contain a pyramidal structure formed by the N,N-bridging triazolato groups. The copper atoms are five-coordinate with a distorted squarepyramidal geometry.…”

Syntheses, Structure Analyses and Thermal Stabilities of Two Schiff Base Metal Complexes

“…3 Besides, the complexes with different nuclearity have been obtained depending on variables such as the co-ligand, anion and the metal-ligand ratio. 4,[21][22][23] For example, using a bitriazole ligand 1- 22 While using 1-(4-hydroxyphenyl)-1,3,4-triazole (L) and copper(II) chloride in EtOH solution, at only Cu∶L molar ratio of 5∶1, two crystalline complexes [Cu 6 (µ-Cl)(µ 3 -OH) 2 -(µ-L) 6 Cl 9 (H 2 O) 3 ]•3H 2 O and [Cu(µ-L)(µ-OH)(H 2 O) 2 ]Cl could be formed. 23 To date, only a limited number of complexes with 1-substituted-1,3,4-triazole have been described, and only a few crystal structures are known.…”