Notes. Correlation between structure and circular dichroism. Structure and absolute configuration of the (–)isomer of lithium (ethylenediamine-N,N′-diacetato-N,N′-di-3-propionato)rhodate(III) pentahydrate

Abstract

In order to determine the geometrical isomerism and absolute configuration of the ion (–)[Rh(eddda)]^–(eddda = ethylenediamine-N,N′-diacetate-N,N′-di-3-propionate) and to correlate the structure with the c.d. spectrum, the X-ray crystal structure analysis of the title compound was carried out. The bright yellow crystals are orthorhombic, space group P2₁2₁2₁, with a= 11.609(2), b= 13.309(1), c= 12.603(2)Å, and Z= 4. The structure was refined on the basis of 2 883 intensities by full-matrix least-squares methods on a SEL 32/27 minicomputer. The refinement terminated at R= 0.016, R_w= 0.020. The structure of this complex is isomorphous with the chromium analogue and comprises the complex anion, lithium ions, and molecules of water. The five-membered glycinate rings are trans and the absolute configuration of the complex is Λ. The trans(O₅)-(–)[Rh(eddda)]^– ion has a negative sign for the lowest energy E(D_4h) c.d. peak and the assignment of the absolute configuration would be reversed, based on a correlation with [Co(edta)]^–(edta = ethylenediaminetetra-acetate) type complexes. The average metal–ligand distances are as follows: Rh–N 2.022(2), Rh–O(eq) 2.045(2), Rh–O(ax) 2.007(2)Å. Interbond angles deviate from +4.1 to –5.1° from the ideal octahedral geometry.