Syntheses, Crystal Structures, and Magnetic Properties of a Series of Defect‐Dicubane Tetranickel(II) Systems with Variable, Mixed, and Interchangeable µ3‐Core Ligands

Abstract

The article describes syntheses, crystal structures and magnetic properties of six defective dicubane type NiII4 clusters of compositions [NiII4(HL1)2(µ3‐X)2(µ1,1‐N3)2(µ1,3‐carboxylato)2]·nH2O (1, X = OMe–, carboxylato = o‐benzoylbenzoato, n = 0; 2, X = {(OMe–)0.83(N3–)0.17}, carboxylato = phenyl acetato, n = 2; 3, X = {(OMe–)0.80(N3–)0.20}, carboxylato = salicylato, n = 0; 4, X = OH–, carboxylato = o‐benzoylbenzoato, n = 2; 5, X = {(N3–)0.58(OMe–)0.42}, carboxylato = o‐benzoylbenzoato, n = 2) and [NiII4(HL1)2(µ1,1,1‐N3)2(µ1,1‐N3)2(N3)2(H2O)2]·4DMF (6), where H2L1 is 2‐Formyl‐6‐{(2‐hydroxy‐1,1‐dimethyl‐ethylimino)‐methyl}‐4‐ethyl‐phenol, and this is the partially hydrolyzed product of initially employed ligand H3L, 2,6‐bis‐{(2‐hydroxy‐1,1‐dimethyl‐ethylimino)‐methyl}‐4‐ethyl‐phenol. Each of the two compartments of each [HL1]– in 1–6 is occupied by a NiII ion, to form a NiII2 fragment. The common bridges between the two metal ions in a dinuclear fragment are µ‐phenoxo of [HL1]– and one µ3‐core ligand (methoxo/hydroxo/mixture of methoxo and µ1,1,1‐azido) while the additional bridge in 1–5 is a µ1,3‐carboxylato. Two dinuclear fragments are interlinked by two µ1,1‐azido and two µ3‐core ligands. Interestingly, the µ3‐methoxo compound 1 and the µ3‐hydroxo compound 4 are interconvertible in both ways as the function of the solvents. Variable‐temperature and variable‐field magnetic studies reveal overall ferromagnetic interactions in each of 1–6.