Properties and Structures of the Five-coordinate Copper(II) and Six-coordinate Nickel(II) Complexes [CuL]·2H₂O∞ and [NiLH₂O]₂, L = N,N′-bis[(2-hydroxy-5-methylphenyl)(4-methylphenyl)methylene]-3-azahexane- 1,6-diamine


The copper(II) and nickel(II) complexes of the potentially pentadentate ligand (2,3-mmbpN) derived from the Schiff base condensation of 3-azahexane-1,6-diamine and 5,4′-dimethyl-2-hydroxybenzophenone have been synthesized and their crystal structures and magnetic and spectral properties determined. For comparison, the copper and nickel complexes of a series of related ligands have also been synthesized and their magnetic and spectral properties determined. The ligands act as pentadentates, in contrast with the coordination reported for some analogous Schiff base ligands with salicylaldehyde. The structures of both the copper and nickel complexes with 2,3-mmbpN are unexpected. The copper environment is very close to trigonal bipyramidal, with the amine nitrogen bond being only 0.1 Å longer than the imine nitrogen bonds. This amine nitrogen bond, at 2.077 Å, is much shorter than the analogous bond in the related complexes [Cu(3,3-mbpN)] (2.374 Å) and [Cu(3,4-cbpN)] (2.291 Å), and this shortening is ascribed to the steric requirements of the ligand. The nickel environment is close to octahedral, with a molecule of water coordinated to the nickel in a position cis to the amine nitrogen. Such coordination has been previously observed for complexes of cobalt(III) but nol for nickel(II). The hydrogen bonding links neighboring molecules to form weakly linked dimers in the nickel complex, [Ni(2,3-mmbpN)·H2O]2, and infinite chains in the copper complex, [Cu(2,3-mmbpN)]·2H2O∞. The crystal structures were determined from full-matrix least-squares refinement of counter data: [Cu(2,3-mmpbN)]·2H2O, space group C2/c, Z = 4, a = 29.128 Å, b = 8.503 (2) Å, c = 13.921 (5) Å, β = 106.63 (2)°, V = 3304 Å3, R = 3.5% for 1718 reflections; [Ni(2,3-mmbpN)H2O], space group P1, Z = 2, a = 10.833 (2) Å, b = 12.63 (1) Å, c = 13.137 (6) Å, α = 116.83 (5)°, β = 91.09 (4)°, γ = 93.91 (6)°, V = 1598 Å3, R = 3.1% for 3118 reflections. © 1979 American Chemical Society.



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© 1979 American Chemical Society (ACS), All rights reserved.