CRYSTAL STRUCTURE AND EPR DATA OF A DINUCLEAR Cu(II) COMPLEX, [Cu(N³) (NCO)diEten]². J. Zukerman-Schpector,¹ O.E. Piro,² E.E. Castellano,³ C.A. De Simone,⁴ D.M. Martino⁵ and C.A. Steren^{5 1}Dept. Qumica, Univ. Federal de Sao Carlos, C.P. 676, 13565-905 Sao Carlos(SP), Brazil, ²Dept. Fisica, Ftad. C. Exactas, Univ. Nacional de La Plata, C.C. 67, 1900 La Plata, Argentina ³Inst. Fisica de Sao Carlos, Univ. de Sao Paulo, C.P. 369, 13560 Sao Carlos, Brazil ⁴Dept. Quimica, Univ. Federal de Alagoas, 57000 Maceio (AL), Brazil, ⁵INTEC (CONICET-UNL), Guemes 3450, 3000 Santa Fe Argentia

The [Cu(N₃)(NCO)(C₁₆N²)]² molecules are arranged as centrosymmetric dimers in which two azide ligands bridge neighboring copper ions in an asymmetric head-on fashion. The Cu(II) ion is coordinated to five nitrogen atoms which form a distorted tetragonal pyramid. At the pyramid base are the two N atoms of a diEten molecule [d(Cu-N)=2.00(1), 2.12(1) Å], an azide end atom [d(Cu-N)= 1.99(1) Å] and a NCO group [d(Cu- N)=1.95(1) Å]. At the pyramid apex is the other, inversion related to the first one, azide N atom in the dimer [d(Cu-N)=2.38(1) Å]. This Cu-N contact links the monomers within a dimer providing a electronic path to transmit the superexchange coupling between the Cu(II) unpaired electrons. Neighboring dimers are coupled y weak N-H..O contacts. Single crystal EPR data at X-band show that the pair of resonances expected for neighboring, magnetically nonequivalents dimers, collapse into a single line, a signature of inter-dimers superexchange coupling. The observed crystal gyromagnetic tensor is used to disclose the electronic and magnetic structure around Cu(II) ions. The compound crystallizes in the space P21/n, with a=8.336(1), b=17.405(3), c=8.376(1) Å, ß=109.73(2)[[ring]] and Z=4.