STEREOCHEMISTRY OF COMPLEXES WITHN-ALKYLATED AMINO ACIDS. XI. CRYSTAL STRUCTURE AND MOLECULAR MECHANICS CALCULATIONS ON RACEMIC AQUABIS(L-N,N-DIMETHYLVALINATO)COPPER(II)

Abstract

Abstract The structure of blue, triclinic (P 1) crystals of a 1:1 mixture of trans-aquabis(L-N,N-dimethylvalinato)copper(II) and its enantiomer was determined by X-ray diffraction methods and refined to R = 0.026. The structure consists of discrete molecules linked with OH–O hydrogen bonds. Coordination around copper(II) is distorted square-pyramidal with valine N and O atoms in the equatorial plane. The O-Cu-OW, O-Cu-N and N-Cu-OW valence angles range from 82.82(7) to 99.11(7)°. Values for O-Cu-O and N-Cu-N are 167.56(8) and 167.59(8)°, respectively. Cu-O [1.932(2), 1.929(2) A] and Cu-N [2.057(2), 2.043(2) A] bond lengths have values similar to those in other copper(II) complexes with N-alkylated amino acids, but the Cu-OW bond length is very short [2.312(2) A]. This was attributed to distortion of the coordination polyhedron, and the apical bond length was quite satisfactorily reproduced with a new theoretical method (N. Raos, J. Mol. Struct., in press.). The shape of the coordination polyhedron was rea...