Syntheses, crystal structures and magnetic properties of a series of μ-phenoxo-μ1,1-carboxylato-μ1,3-carboxylato trinickel(ii) compounds

Abstract

The work in this report describes the syntheses, characterization, crystal structures and magnetic properties of eight linear trinickel(II) compounds of the composition [Ni^II₃(L^sal–pyr)₂(propionate)₄] (1), [Ni^II₃(L^sal–pyr)₂(benzoate)₄]·CH₃CN (2), [Ni^II₃(L^sal–pip)₂(acetate)₄]·2CH₃CN (3), [Ni^II₃(L^sal–pip)₂(propionate)₄] (4), [Ni^II₃(L^sal–pip)₂(benzoate)₄]·CH₂Cl₂ (5), [Ni^II₃(L^sal–mor)₂(propionate)₄] (6), [Ni^II₃(L^sal–mor)₂(benzoate)₄]·3CH₂Cl₂ (7) and [Ni^II₃(L^sal–mor)₂(o-Cl-benzoate)₄]·2CH₃CN·2H₂O (8), where HL^sal–pyr, HL^sal–pip and HL^sal–mor are the 1 : 1 condensation products of salicylaldehyde and 1-(2-aminoethyl)-pyrrolidine, 1-(2-aminoethyl)-piperidine and 4-(2-aminoethyl)-morpholine, respectively. One-half of the trinuclear core in each complex is symmetry related to the second part due to the presence of an inversion centre on the central metal ion and so the terminal nickel⋯central nickel⋯terminal nickel angle is 180°. The terminal and central nickel(II) ions are triply bridged by a phenoxo, a μ_1,1-carboxylato and a μ_1,3-carboxylato moiety. The μ_1,1-carboxylato also acts as a chelating ligand for the terminal metal ion. Both the variable-temperature (2–300 K) susceptibilities at a fixed field strength of 0.1 T and variable-field (up to 7 T) magnetization at different fixed temperatures (2–10 K) were recorded. The magnetic data indicate the ferromagnetic interaction in all the cases with J (Ĥ = −2J_ij∑S_iS_j) values ranging between 2.37 and 3.89 cm⁻¹ and the single-ion zero-field parameter (D) ranging between 7.21 and 8.94 cm⁻¹. Satisfactorily simulation of both the χ_MT vs. T and M vs. H data has been obtained. Comparison of the structures and magnetic properties of compounds 1–8 with those of the previously published related systems reveals some interesting aspects.