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Stereochemical changes by chelatation: N,N-Butylenebissalycilaldimine and its copper complex

N,N-butylenebissalicylaldimine (I) was prepared from 1,4-diaminobutane and salicylaldehide. The copper complex was prepared in a template reaction using NaOH as a deprotonation agent. The crystals of (II), obtained by slow evaporation, consist of two discrete molecules of copper complex bridged by a sodium ion. (I) C18H20N2O2, P 21/c, a = 15.345(1) A, b = 5.8799(5) A, c = 8.9744(8) A, beta = 90.145(8) o, V = 809.72(8) A3, Z = 2, Dc = 1.216 gcm-3, lambda(MoKa) = 0.71073 A, R = 0.051 and wR = 0.089 for 1179 independent reflections with Inet gt 2s Inet. (II) C36H36N5NaCu2O7, P bcn, a = 16.908(5) A, b = 11.409(4) A, c = 18.172(5) A, V = 3505.4(19) A3, Z = 4, Dc = 1.517 gcm-3, lambda(MoKa) = 0.71073 A, R = 0.039 and wR = 0.058 for 1975 reflections with Inet gt 2s Inet. The main feature of (I) is the existence of an O-HˇˇˇN intramolecular chelate ring hydrogen bond. It was assumed that the length of the bridging chain in (I) could introduce certain strain in the molecule of its CuII complex thus influencing to the geometry of copper atom coordination sphere. The sodium ion bridges two metal complex molecules via strong Na+ˇˇˇO electrostatic attractions. The nitrate ion completes the Na+ surroundings to an irregular octahedron. Perhaps the presence of an alkaline metal ion partially stabilizes the strained conformation of the ligand.

Tetradentate Schiff base; copper complex; stereochemistry; X-ray crystal structure

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