Chiral metal complexes 3. The pH-controlled equilibrium of diastereoisomeric pairs of ternary cis-Ru(II)-diimine complexes witL-glutamic acid

Robert S. Vagg*, Peter A. Williams

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

The compounds of general formula Δ, Λ-[Ru(diimine)2(L-glu)]·nH2O [where L-glu is the L-glutamate di-anion and diimine is 1,10-phenanthroline (n = 6) or 2,2′-bipyridyl (n = 5)] have been isolated and their diastereoisomeric pairs resolved using chromatographic methods. The Λ-isomer of each species spontaneously inverts in neutral aqueous solution in the presence of light. The equilibrium constants at 298 K for the reaction Δ-[Ru(diimine)2(L-glu)]°aq ⇌ Λ-[Ru(diimine)2(L-glu)]°aq are 0.64(5) and 0.56(7) for the phen and bipy complexes respectively. From acidic solutions the compounds of general form Δ,Λ-[Ru(diimine)2(L-gluH)]ClO4·3H2O [where L-gluH is the monohydro-L-glutamate anion] have been obtained. The corresponding equilibrium constants for these cationic species are close to unity, being 1.03(8) and 1.17(17) for the phen and bipy complexes respectively. Equilibrium mixtures of these cationic species, upon deprotonation, deracemize with respect to the metal centre to yield solids enriched in the Δ-diastereoisomers, consistent with equilibration of the neutral form. Possible contributions to the chiral discriminations observed for these reactions are discussed.

Original languageEnglish
Pages (from-to)101-105
Number of pages5
JournalInorganica Chimica Acta
Volume58
Issue numberC
DOIs
Publication statusPublished - 1982

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