STEREOCHEMISTRY OF COMPLEXES WITH N-ALKYLATED AMINO-ACIDS .8. CRYSTAL-STRUCTURE AND CONFORMATIONAL-ANALYSIS OF AQUABIS(L-N,N-DIMETHYLTHREONINATO)COPPER(II) DIHYDRATE

The structure of blue, monoclinic (space group P2(1)) crystals of aqua bis(L-N,N-dimethylthreoninato)copper(II) dihydrate was determined by X -ray diffraction and refined to R = 0.030. The coordination around the copper(II) atom is distorted sguare-pyramidal with threonine N and O atoms in trans orientations (Cu-O 1.930(3) and 1.926(3)Angstrom, Cu-N 2.042(3) and 2.055(3)Angstrom, O-Cu-O 163.9, N-Cu-N 164.0 degrees) and apical water (Cu-O(W) 2.206 Angstrom). The shape of the coordination polyhedron was reasonably well reproduced with molecular mechanics cal culations, yielding root-mean-square deviations of ten Valence angles around copper to 4.5 degrees. The calculated strain energy of the crys tal conformation is about 21 kJ mol(-1) higher than the energy of the most stable conformer. This was tentatively attributed to the addition al stabilization of molecular conformation by intermolecular hydrogen bonds in the solid state.