HEXAFLUOROSILICATE COORDINATION TO THE ANTITUMOR COPPER(II) SALICYLALDEHYDE BENZOYLHYDRAZONE (H(2)L) SYSTEM - SINGLE-CRYSTAL X-RAY STRUCTURE OF [(CU(HL)H2O)(2)SIF6]CENTER-DOT-2H(2)O

The complex [{Cu(HL)H2O}SiF6]. 2H(2)O (H(2)L = salicylaldehyde benzoylhydrazone) has been prepared from the reaction of CuF2 . 2H(2)O in concentrated HF with ethanolic solution of H(2)L SiF62- was generated by the in situ reaction of fluoride on silica. The complex has been characterized by a range of physicochemical techniques and the crystal and molecular structure determined by single-crystal X-ray diffraction. The crystals of [{Cu(HL)H2O}2SiF6]. 2H(2)O are monoclinic, space group C2/c, with a=13.677(5), b=11.876(3), c=20.336(7) Angstrom, beta=105.92(3)degrees and Z=4. The complex is a discrete centrosymmetric dimer, the monomeric units being bridged by the coordinated SiF62- anion with the Si lying on the inversion centre. The copper atom has a distorted square-pyramidal geometry with three donor atoms (ONO) from the tridentate monoanionic HL(-) ligand and the fourth in-plane donor (O), from a water molecule. The fifth position is occupied by a less strongly bound fluorine from the bridging SiF62- anion. Alternate stacking of the dimeric units which would allow overlap of pi electron density as well as H bonding involving all of the hexafluorosilicato F atoms appears to be important for the stability of the complex in the solid.