Stereochemistry and Reactivity of Metal–Schiff-base Complexes. I. Preparation and Thermodynamic Stereoselectivity of Mixed Ligand Cobalt(III) Complexes Containing N,N′-Ethylenebis(salicylideneamine) Dianion (sal2en) or N,N′-Ethylenebis(7-methylsalicylideneamine) Dianion (7,7′-Me-sal2en) and l-Amino Acid Anion

Abstract

Abstract Two series of new mixed ligand cobalt (III) complexes with the general formulas of [Co(sal2en)(l-aa)] and [Co(7,7′-Me-sal2en)(l-aa)] (where l-aa=anion of l-ala, l-val, l-leu, l-isoleu, l-met, l-thr, l-phe, l-tyr, or l-trp) have been prepared and characterized. All are labile for both isomerization and substitution reactions and each exists in an equilibrium mixture of ΛL- and ΔL-cis-β1(fac)-isomers (ΛL>ΔL)in methanol. The isomer’s ratios, ΛL/ΔL were estimated from their PMR spectra, and the following facts were found: The increasing order of the ratios is l-ala∼l-met∼l-leu<l-val<l-isoleu<l-thr<l-phe∼l-tyr<l-trp, and the ratios are larger in 7,7′-Me-sal2en-complexes than in sal2en-complexes for each amino acid.