Stereochemistry of Complexes withN-Alkylated Amino Acids. IV. Crystal Structure of DisorderedD,L-BIS(N,N-Diethyl-α-Alaninato)Copper(II); Molecular Mechanics Calculations and Conformational Analysis of Copper(II)N,N-Diethylalaninates

Abstract

Abstract The crystal structure of a new, red, triclinic modification of (D,L-N,N-diethyl-α-alaninato)copper(II) was solved by X-ray diffraction methods and refined to R = 0.035. The structure contains discrete molecules disordered over two sites in a 72:28 ratio with the copper atom on an inversion centre. The copper, oxygen and nitrogen atoms and one carbon atom are common to both molecules while six carbon atoms are disordered over two sites. The coordination around the copper atom is irregular square-planar with oxygen and nitrogen atoms necessarily trans. Interatomic distances [Cu-O 1.910(2)A and Cu-N 2.033(2)A] are comparable with those found in related crystal structures. The two independent molecules A and B (which are disordered about an inversion centre) have identical conformations in the lattice, molecular mechanics calculations correctly predict the crystal (most stable) conformation of D,L-bis(N,N-diethyl-α-alaninato)copper(II); the conformation predicted for the L,L isomer appears to be a tr...