Influence of the Peripheral Ligand Atoms on the Exchange Interaction in Oxalato-Bridged Nickel(II) Complexes:  An Orbital Model. Crystal Structures and Magnetic Properties of (H₃dien)₂[Ni₂(ox)₅]·12H₂O and [Ni₂(dien)₂(H₂O)₂(ox)]Cl₂

Abstract

Two nickel(II) complexes of formula (H(3)dien)(2)[Ni(2)(ox)(5)].12H(2)O (1) and [Ni(2)(dien)(2)(H(2)O)(2)(ox)]Cl(2) (2) (dien = diethylenetriamine and ox = oxalate dianion) have been synthesized and characterized by single-crystal X-ray diffraction. 1 crystallizes in the orthorhombic system, space group Abnn, with a = 15.386(4) Å, b = 15.710(4) Å, c = 17.071(4) Å, and Z = 4. 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 10.579(1) Å, b = 7.258(1) Å, c = 13.326(1) Å, beta = 93.52(3) degrees, and Z = 2. The structures of 1 and 2 consist of dinuclear oxalato-bridged nickel(II) units which contain bidentate oxalate (1) and tridentate dien in the fac-conformation (2) as terminal ligands. Both features, oxalato as a peripheral ligand and dien in the fac-conformation (instead of its usual mer-conformation), are unprecedented in the coordination chemistry of nickel(II). The nickel atom is six-coordinated in both compounds, the chromophores being NiO(6) (1) and NiN(3)O(3) (2). The Ni-O(ox) bond distances at the bridge (2.072(4) Å in 1 and 2.11(1) and 2.125(9) Å in 2) are somewhat longer than those concerning the terminal oxalate (2.037(5) and 2.035(3) Å in 1). Magnetic susceptibility data of 1 and 2 in the temperature range 4.2-300 K show the occurrence of intramolecular antiferromagnetic coupling with J = -22.8 (1) and -28.8 (2) cm(-)(1) (J being the parameter of the exchange Hamiltonian H = -JS(A).S(B)). The observed value of -J in the investigated oxalato-bridged nickel(II) complexes, which can vary from 22 to 39 cm(-)(1), is strongly dependent on the nature of the donor atoms from the peripheral ligands. This influence has been analyzed and rationalized through extended Hückel calculations.

New 1,3,4‐Oxadiazolecopper(II) Derivatives Obtained from Thiosemicarbazone Complexes

“…It has been established that the less electronegative is the donor atom in the basal plane the stronger the induced antiferromagnetic coupling is, due to a greater hybridization of the d x 2 Ϫy 2 metal orbital towards the bridge. [46,47] Figure 13 shows a good accordance between the average J values and Pauling's electronegativity of the compounds in Table 6. Conversely, the relationship between J and other structural parameters is not evident even for a given X-donor set.…”

Antiferromagnetic dimers of Ni(II) in theS=1spin-ladderNa2Ni2(Mennerich1, Klauss2, Broekelmann3 et al. 2006Phys. Rev. B263190View full textAdd to dashboardCite

“…In the literature several µ-1,2,3,4 oxalato-bridged Ni(II) dimer and chain systems are reported (see e.g. 22,23 and references therein) with J values in the range of 20 to 42 K. The value of 43 K in SNOX is at the upper limit of the reported range.…”

Rational Design of Homo and Hetero Hexanuclear Coordination Compounds: Syntheses and Magnetic Properties of [Cu2IIM4II] (M = Cu, Ni) Species and the Crystal Structure of {[Cu(tmen)(H2O)]2[Cu(tmen)]2[Cu2L](H2O)}(ClO4)4 · 2 H2O

“…Recently, the role of peripheral ligand on the coupling constant has been studied in oxalato-bridged nickel(II) complexes. [29] With four nitrogens as donor atoms, the peripheral cyclam ligand is expected to induce a coupling close to that of the cth ligand (cth ϭ 2,4,4,9,9,11-hexamathyl-1,5,8,12-tetraazacyclotetradacane), that is -2470 yJ (-124.5 cm -1 ). [13] This is not observed experimentally, but in the absence of an Xray analysis of the compound, it is not possible to give a satisfactory explanation to this relatively small value of the exchange interaction through the oxamato bridge.…”