Λ-[Co((S,S)-dpen)3]3+ 2I-B(C6F5)4-: A Second Generation Air- and Water-Stable Chiral Solvating Agent for Chirality Sensing (dpen = NH2CHPhCHPhNH2).

Abstract

When CDCl3 solutions of chiral racemic molecules containing moderately Lewis basic functional groups are treated with the chiral solvating agent (CSA) Λ-[Co((S,S)-dpen)3]3+ 2I-B(C6F5)4- (Λ-(S,S)-13+ 2I-B(C6F5)4-), baseline-resolved NMR signals are observed for the enantiomers (29 diverse analytes). Only 0.62-100 mol % loadings are required (avg 14.5 or 11.6% for 24 analytes common to all tested CSAs). The overall performance is superior to those reported earlier for analogous salts with 2X-BArf- counter anion sets [BArf = B(3,5-C6H3(CF3)2)4]; 1.0-100 mol % loadings, avg 32.6% (X = Cl) or 14.0% (X = I) for 24 common analytes) and a new 2TfO-B(C6F5)4- salt (1.1-100 mol % loadings; avg 31.0% for 24 common analytes), including extensions to prochirality sensing. The effect of the solvent (Δδ in CDCl3 > CD2Cl2) is analyzed. The new CSAs are prepared in two steps from Λ-(S,S)-13+ 3Cl- by standard anion metathesis recipes (90-98% overall). The broad analyte scope and modest loading requirements for the title CSA distinctly surpass those of others in the literature.