SIMILARITY OF ORTHO-ZBENZOATE ANIONS IN THE ISOTYPIC STRUCTURES OF -ZBENZOATO-O)DI(1,3-DIAMINOPROPANE-N,N')COPPER(II) COMPLEXES (Z=CL OR BR)

The structures of Zbenzoato-O)bis(1,3-diaminopropane-N,N')copper(II) ( Z=Cl or Br) complexes were determined by single crystal X-ray methods. (1) [Cutn(2)(2ClbzO)(2)], C20H28Cl2CuN4O4, M-r=522.92, orthorhombic, space group Pbca No. 61, a=10.585(3), b=21.414(2), c=10.271(3) Angstro m, V=2328.0(9) Angstrom(3), Z=4, D-c=1.49 g cm(-3); (2) [Cutn(2)(2Brbz O)(2)], C20H28BT2CuN4O4, M-r=611.82, orthorhombic, space group Pbca No . 61, a=10.573(2), b=21.378(3), c=10.413(2) Angstrom, V=2353.8(6) Angs trom(3), Z=4, D-c=1.73 g cm(-3), tn=1,3-diaminopropane, 2ZbzO=ortho-su bstituted halogenobenzoate. The compounds are isotypic to a high degre e. All of the bond lengths and angles, with the exception of those con cerning the carboxylate groups and halogen-C(arom) bonds are the same within the experimental errors in the two compounds. The central coppe r(II) ion sits at a centre of symmetry and displays distorted pseudo-o ctahedral coordination with axial elongation, The crystal structures c onsist of layers formed by halogen-halogen interactions and hydrogen b onding chains mediated by amine and carboxylate groups. Each intermole cular chain can be described as C(6). Owing to symmetry, they form rin gs formulated as R-4(4)(24). The observed isotypism between the comple x units in the two compounds is probably mediated by the hydrogen bond ing. The ab initio calculations carried out for the 2-substituted benz oic acids and their anions at the RHF/6-311++G(d) level of theory are in accordance with the experimental similarity found for the 2-bromo a nd 2-chloro benzoate anions. The deviations in the angles of the aroma tic ring are explained by natural bond order analyses as intramolecula r interactions between two of the three lone pairs of a halogen substi tuent and a neighbouring aromatic antibonding molecular orbital in the aromatic ring.