Bond-valence approach to the copper-copper and copper-oxygen bonding in binuclear copper(II) complexes: Structure of tetrakis(2-fluorobenzoato-O,O ')-bis (2-fluorobenzoate-O) dicopper(II)

The crystal and molecular structure of tetrakis(2-fluorobenzoato - O,O')-bi s(2-fluorobenzoate-O) dicopper(II) - C42H26Cu2F60O12 - has been determined at room temperature. The blue-green crystals are monoclinic, space group P2 (1)/n (No. 14), with unit cell parameters a = 10.633(3) Angstrom, b = 12.52 8(3) Angstrom, c = 14.729(3) Angstrom, beta = 91.62(4)degrees, Z = 2, D-m = 1.62 and D-x = 1.64 g/cm(3). The final R value for independent reflections is equal to 0.045. The structure consists of two centrosymmetric units [Cu -2(2 FbzO)(4)(2 HFbzO)(2)] (abbreviation 2 FbzO stands for I-fluorobenzoate , abbr. 2 HFbzO for 2-fluorobezoic acid). These units are mutually held by Van der Waals forces. Within the binuclear unit the Cu atom is pentacoordin ated by four carboxylic O atoms in the basal plane of tetragonal pyramid (C u-O bond lengths bring 1.962(3) Angstrom, 1.963(2) Angstrom, 1.958(2) Angst rom and 1.996(2) Angstrom) and one apical O atom from HFbzO molecule, with Cu-O bond length 2.193(2) Angstrom. The apical Cu(II)-O bond length predict ed by bond valence method is 2.16 Angstrom. The Cu ... Cu distance is 2.608 6(8) Angstrom and the displacement of Cu atom from the basal plane is 0.190 5(6) Angstrom. Nonbonding character of Cu(II)... Cu(II) contact in 16 binuc lear carboxylic complexes is proved.