Nickel complexes with tris(2-aminoethyl)amine (tren): [Ni3(tren)4(H2O)2][Cr(ox)3]2·6H2O (ox = oxalate), {[Ni2(tren)3][ClO4]4·H2O}n, and [Ni2(tren)2(aepd)][ClO4]4·2H2O (aepd = N-(2-aminoethyl)pyrrolidine-3,4-diamine). Synthesis, structure and magnetism†

Abstract

Reaction of K₃[Cr(ox)₃] (ox = oxalate) with nickel(II) and tris(2-aminoethyl)amine (tren) in aqueous solution resulted in isolation of the bimetallic assembly [Ni₃(tren)₄(H₂O)₂][Cr(ox)₃]₂·6H₂O. The polymeric complex {[Ni₂(tren)₃][ClO₄]₄·H₂O}_n has been prepared by reaction of nickel(II) perchlorate and tren in aqueous solution. From the same reaction mixture the complex [Ni₂(tren)₂(aepd)][ClO₄]₄·2H₂O (aepd = N-(2-aminoethyl)pyrrolidine-3,4-diamine), in which a bridging tren ligand contains a carbon–carbon bond between two arms forming a substituted pyrrolidine, has been isolated. The complexes have been characterized by X-ray crystallography. The magnetic susceptibility (300–4.2 K) and magnetization data (2, 4 K, H = 0–5 T) for {[Ni₂(tren)₃][ClO₄]₄·H₂O}_n (300 K , 4.23 µ_B) exhibit evidence of weak antiferromagnetic coupling and zero field splitting (2J = –1.8 cm^–1; |D| = 2 cm^–1) at low temperature. For [Ni₃(tren)₄(H₂O)₂][Cr(ox)₃]₂·6H₂O the susceptibility data at 300 K are indicative of uncoupled nickel(II) and chromium(III) sites with zero-field splitting and intramolecular antiferromagnetic coupling predicted at low temperature.