Hexafluorosilicate coordination to the antitumour copper(II) salicylaldehyde benzoylhydrazone (H2L) system: single-crystal X-ray structure of [{Cu(HL)H2O}2SiF6]·2H2O

Abstract

The complex [{Cu(HL)H2O}2SiF6]·2H2O (H2L = salicylaldehyde benzoylhydrazone) has been prepared from the reaction of CuF2·2H2O in concentrated HF with ethanolic solution of H2L. SiF6 2- 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]·2H2O are monocliic, space group C2/c, with a = 13.677(5), b = 11.876(3), c = 20.3 A ̊, β = 105.92(3)° and Z = 4. The complex is a discrete centrosymmetric dimer, the monomeric units being bridged by the coordinated SiF6 2- 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 SiF6 2- anion. Alternate stacking of the dimeric units which would allow overlap of π 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. © 1995.