Magnetic interactions in metal complexes of binucleating ligands. 2. Synthesis and properties of binuclear copper(II) compounds containing exogenous ligands that bridge through two atoms. Crystal and molecular structure of a binuclear .mu.-pyrazolato-N,N'-bridged dicopper(II) complex of 1,3-bis(salicylideneamino)propan-2-ol

Abstract

The synthesis and characterization of a series of binuclear copper(II) complexes of binucleating ligands formed by the condensation of pyridine-2-carbaldehyde, salicylaldehyde, and acetylacetone with 1,3-diaminopropan-2-ol and 1,5-diaminopentan-3-ol are reported. All compounds have an endogenous bridging ligand alkoxide group and, in addition, have bridging exogenous ligands such as pyrazolate, 3,5-dimethylpyrazolate, and acetate ions that bridge through two atoms. The crystal and molecular structure of the µ-pyrazolate-bridged dicopper(II) complex of l,3-bis(salicylideneamino)propan-2-ol of formula C20H20CUN4O4 having space group Pbcn and cell dimensions a = 14.983 (2) A,b = 8.276 (5) A, and c = 31.163 (4) Á was solved for 1033 non-zero structure factors (/ > 2.5 (1)). The crystal system is orthorhombic with Z = 8. Full-matrix least-squares refinement gave a final R factor of 0.0762. The ligand is binucleating, and the two copper(II) ions are bridged by the secondary alkoxo group and the pyrazolate moiety. Both copper(II) centers have essentially planar coordination of N202 donor sets. The compound contains an uncoordinated molecule of water. There are no significant intermolecular interactions between neighboring binuclear entities. The intramolecular Cu---Cu distance is 3.359 (4) Á. Magnetic susceptibilities for all the compounds in the solid state are measured over the temperature range 4.2-300 K. The magnetic behavior may be satisfactorily treated by the Bleaney-Bowers equation for a spin-coupled 5=1/2 system in which the singlet-triplet separation is 2J. When the magnetic data for a series of previously reported analogues having single-atom bridges and the present two-atom-bridged species are compared, it is observed that -J decreases in the order OR" = pyrazolate > acetate ~OH" > Cl". Structural data indicate that distortions from trigonal-planar toward pyramidal geometry of the endogenous alkoxo bridging ligand lead to a less negative value for J. In several compounds, this effect leads to net ferromagnetism. the active center in the type 3 copper proteins5*"8 has encouraged(1) (a) La Trobe University, (b) Monash University, (c) The University of Adelaide, (d) Deceased, March 18, 1985.(2) (a) Barnes,

Macromolecular Salen Catalyst with Largely Enhanced Catalytic Activity

“…Attempts to prepare dinuclear copper(II) complexes containing other bridging anions, including gluconate, gallate, anthracene-9-carboxylate, terephthalate, formate, or malate, have failed so far. Similar observations were reported for the preparation of the nonpolymerizable dinuclear copper(II) complex { N , N ‘-1,3-bis[(2-hydroxy)benzylideneamino]propan-2-ol}ato (μ-acetato) dicopper(II) diperchlorate [ 4 , Cu 2 (bsdpo)(Ac)], derived from N , N ‘-1,3-bis[(2-hydroxy)benzylideneamino]propan-2-ol ( 5 , bsdpo) (Figure ) 1 Structures of nonpolymerizable backbone ligand 5 and the dinuclear copper(II) complex 4 derived thereof. …”

Molecular enneanuclear CuII phosphates containing planar hexanuclear and trinuclear sub-units: syntheses, structures, and magnetism

“…In practice, the two exchange constants in the isosceles triangle will have very large values and will be antiferromagnetic, leading also to a frustrated spin ground state of S = 1/2 for the Cu9 complex. In the literature there are abundant references where such NN bridging between two metal centres is part of a pyrazole, triazole, [49][50][51][52][53] or pyridazine 54 ligand. These types of ligands have been used a lot in Cu(II) complexes, since they usually afford effective exchange pathways for antiferromagnetic coupling.…”

Mixed-Valent Trinuclear CoIII-CoII-CoIII Complex with 1,3-Bis(5-chlorosalicylideneamino)-2-propanol

“…In the crystals, the Schiff bases take a "bent" [11][12][13][14][15]34] or "folded" [16] structure with the salicylideneaminomethyl moieties being close to planar. When the Schiff-base ligands are coordinated to two metal atoms with two phenolic-oxygen, two imino-nitrogen, and one bridging alkoxido-oxygen donor atom with a pair of tridentate O, N, O-chelates, Mn III 2 , Fe III 2 , Co III 2 , Ni II 2 , and Cu II 2 complexes were reported as this type of dinuclear species [17][18][19][20][21][22][23][24][25][26][27][28][29]. On the other hand, these Schiff-base ligands form mononuclear metal species with a tetradentate O, N, N, O-chelate as shown in the case for 1,3-bis(5chlorosalicylideneamino)-2-propanol in Figure 1b, where the central alcohol group remains protonated and does not participate in coordination to the metal center.…”