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STRUCTURE OF DIMERIC [N,N'-OCTYLENEBISSALICYLALDIMINATO]COPPER(II)

The stereochemistry of copper(II) complexes with tetradentate Schiff bases made from salicyladehyde and symmetrical alkyl diamines depends to the great extent on the ligand bridging chain length. Monomeric species will always be formed if the number of methylene groups in the bridge does not exceed four. The rigidity of the ligand with six or eight CH_2 groups is significant and dimeric copper(II) complex molecules are exclusively possible. Nevertheless, in both monomeric and dimeric complex molecules the central metal atom surrounding is distorted tetrahedral differing only in the proportion of the deformation. Crystal Data: C_44H_52Cu_2N_4O_4 ^. 1/2 H_2O. M_r = 837.02, Monoclinic, space group C2/c, a = 23.191(2), b = 14.071(2), c = 28.006(3) A, b = 105.956(8)^o, V = 8786(2) A^3, Z = 8, D_c = 1.252 g cm^-^3, F(000) = 3512, l(MoK_a) = 0.7107 A, m(MoK_a) = 1.01 mm^-^1. A total of 7721 independent reflections were measured. The 1700 reflections with I_net => 2sI_net were considered observed and used in the refinement. The final R value was 0.071 with an wR value of 0.112. No absorption corrections were applied. The unit cell contains two crystallographically independent, stereochemically totally different dimeric molecules having imposed 2-fold symmetry. The copper atom coordination spheres can be described as very flattened tetrahedra with interplanar O-Cu-N angles being 33.9 ^oand 35.5 ^o, respectivelly. The bulkiness of the molecules accounts for certain slight positonal disorder in octylene chains and the solvent accessible area at 0, 1/4, 1/4, where a disordered water molecule with the population parameter 0.5 was found after recrystallisation from dioxane. More reflection data for a more reliable refinement will be collected using a larger crystal in due course.

Dimeric copper(II) complexes; tetrahedral coordination; X-ray structure determination

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