PHENOBARBITURATE COMPLEXES OF COPPER(II) - CRYSTAL-STRUCTURE OF NA-2[CU(PHENOBARBITURATE)(4)] COMPLEX - A SYMMETRICAL SQUARE-PLANAR CUN4 CHROMOPHORE

The x-ray crystal structure of Na-2[Cu(phenobarbiturate)(4)] has been determined, in spite of the difficulties in maintaining single crystal s. The complex crystallizes in space group P4/n cc with a = 16.790(7) Angstrom, b = 16.790(7) Angstrom, c = 20.56(1) Angstrom, V = 5796(6) A ngstrom(3), and Z = 4. The structure has been refined to R = 0.090. Th e Cu(II) ion is coordinated to four deprotonated phenobarbiturate liga nds in a symmetric square planar geometry. The four Cu-N bond distance s are 1.96(1) Angstrom and the N-Cu-N bond angles are exactly 90.0 deg rees. The Na ions are surrounded by four carbonyl oxygen atoms from fo ur phenobarbiturate ligands and four solvent water oxygen atoms in a c ubic geometry. The interpretation of the spectral properties previousl y reported is related to the crystal structure.