Hexafluorosilicate coordination to the antitumour copper(II) salicylaldehyde benzoylhydrazone (H 2L) system: single-crystal X-ray structure of [{Cu(HL)H 2O} 2SiF 6]·2H 2O

Abstract

The complex [{Cu(HL)H 2O} 2SiF 6]·2H 2O (H 2L = salicylaldehyde benzoylhydrazone) has been prepared from the reaction of CuF 2·2H 2O in concentrated HF with ethanolic solution of H 2L. SiF 6 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)H 2O} 2SiF 6]·2H 2O 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 SiF 6 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 SiF 6 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.