Relation Between Magnetic, Spectroscopic, and Structural Properties of Bis[chloro(N-isopropyl-2-hydroxybenzylidene)aminato-μ-O-copper(II)] and Bis(N-isopropyl-2-hydroxybenzylideneaminato)copper(II)


The crystal and molecular structure of the dimeric complex bis[chloro(N-isopropyl-2-hydroxybenzylidene)aminato-μ-O-copper(II)], [Cu(ips)Cl]2, has been determined (P1, Z = 2, a = 7.432 (4) Å, b = 7.867 (9) Å, c = 10.740 (4) Å, α = 81.87 (5)°, β = 84.52 (4)°, γ = 63.41 (6)°, V = 551 Å3, R = 4.0%, 2480 reflections), and the structure of the monomeric bis(N-isopropyl-2-hydroxybenzylideneaminato)copper(II), Cu(ips)2, has been redetermined (Pcab, Z = 8, a = 12.830 (3) Å, b = 14.596 (9) Å, c = 20.714 (4) Å, V = 3879 Å3, R = 4.2%, 1587 reflections). The ligand environments are distorted from square-planar toward tetrahedral, the distortion being greater in the case of the monomeric complex which is closer to tetrahedral than planar. Thus, in Cu(ips)2 the steric constraint which is the main cause of distortion from planarity outweighs the combination of the lesser steric effects but slightly greater electrostatic repulsion in [Cu(ips)Cl]2. The results are in good keeping with the hypothesis that the strength of antiferromagnetic interaction between the copper atoms (as measured by the singlet-triplet separation, -2J) in [Cu(ips)Cl]2 and related complexes is decreased with increasing tetrahedral distortion. Comparison with related binuclear complexes suggests that the isopropyl substituent is responsible for the distortion of the copper environment in [Cu(ips)Cl]2 and therefore also for the relatively small -2J value and a downfield shift of characteristic d-d transitions. Changes in Cu-O-Cu bridging angles are found to be relatively unimportant in such complexes.



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