The Absolute Configuration of the (+)546-β-Oxalato[(6R,8S)-dimethyl-2,5,9,12-tetraazatridecane]cobalt(III) Ion, (+)546-β-[Co(ox)(N,N′-Me2-R,S-2,3″,2-tet)

Abstract

Abstract The crystal and molecular structure of (+)546-β-[Co(ox)(N,N′-Me2-R,S-2,3″,2-tet)]+ has been determined from three-dimensional intensity data collected by counter methods. The structure has been refined by least-squares techniques to an R factor of 5.9% for 838 reflections above the background. The red violet crystals are orthorhombic, with a space group of P212121, with Z=4 (Dm=1.501, Dc=1.505 g/cm3), and with cell constants of a=14.175(5), b=18.591(2) and c=7.747(4) Å. The complex ion has the Δ absolute configuration, which was determined by the Bijvoet method. The quadridentate ligand, N,N′-Me2-R,S-2,3″,2-tet), is coordinated to the Co via 4 N atoms in the cis-β configuration, yielding two terminal 5-membered chelate rings with the λ conformation and a central 6-membered ring with a chair conformation (both C–CH3 groups are equatorial). The secondary N atoms have R chirality except for one terminal N atom, the absolute configuration of which is S. The N(S)–CH3 group in the “out-of-plane” 5-membered ring is equatorial, whereas the N(R)–CH3 group in the other ring has an axial disposition.