The crystal and molecular structure of a five-covalent copper(II) complex

The crystal and molecular structure of a five-co-ordinated copper(II) complex has been determined by X-ray diffraction methods. The complex has the formula [Cu(bpe,MeOH)Br]ClO4 where bpe represents the Schiff base formed by the condensation of two moles of pyridine-2-carbaldehyde with one of ethane-1,2-diamine. The unit cell is monoclinic with dimensions a= 9·28 ± 0·03, b= 13·22 ± 0·04, c= 16·05 ± 0·05 A, β= 98·3 ± 0·3°, space group P21/c, with Z= 4. The structure was determined from three-dimensional Patterson, Fourier, and difference syntheses and refined by least squares. The crystal is built up of copper(II) complex cations and perchlorate anions, the copper atom being surrounded by four nitrogen atoms of the methanol–Schiff-base quadridentate ligand and a bromine atom in an arrangement intermediate between a square pyramid and a trigonal bipyramid. All five atoms are at normal covalent distances from the copper atom. The methanol molecule is added across one of the imine groups of the Schiff base, resulting in a less strained arrangement of the quadridentate ligand about the copper.