Co-ordination behaviour of N-carboxymethylpseudoephedrine: crystal structures of seven-co-ordinated cadmium(II) and fac-RS-octahedral copper(II) complexes

Abstract

Co-ordination compounds of N-[2-hydroxy-1(R)-methyl-2(R)-phenylethyl]-N-methylglycine (N-carboxymethylpseudoephedrine, Hcpse) with copper(II), cobalt(II) and cadmium(II) have been prepared and characterised. Crystal structures of copper and cadmium complexes were obtained. In the compound [Cu(cpse)₂]·H₂O, two cpse are co-ordinated in a tridentate mode giving place to a fac-RS-octahedral geometry. The monomeric compound [Cd(cpse)₂(H₂O)] has an uncommon seven-co-ordinate geometry with one cpse bonded in a similar arrangement to that of the copper(II) compound, with an oxygen from the carboxylate group in an apical position. The second cpse molecule is co-ordinated with all three atoms in the equatorial plane, the remaining axial position of the distorted pentagonal bipyramid being occupied by a water molecule. As for the latter complex, the metal centre of [Cd(cpse)Cl(H₂O)]·H₂O·dmso (dmso = dimethyl sulfoxide) presents a distorted pentagonal-bipyramidal geometry where the apical positions are occupied by a water molecule and a chloride ion. The tridentate cpse ligand lies in the equatorial plane and the co-ordination sphere is completed by a chelating carboxylic group from another cpse ligand. Each carboxylate group of cpse is bridging two different cadmium atoms, forming a zigzag chain in a polymeric structure.