Chromatographic approach to study the configurational stability of Ni(II) complexes of amino‐acid Schiff bases possessing stereogenic nitrogen

Abstract

Herein, we disclose the design of a model Ni(II) complex of glycine Schiff base possessing single-nitrogen stereogenic center, which was successfully used for high-performance liquid chromatography (HPLC)-assisted assessment of its configurational stability. The major finding is that the configurational stability of the Ni(II)-coordinated nitrogen is profoundly dependent on the reaction conditions used, in particular the solvent, and can range from inconsequential (t ½ less than 5 min) to virtually completely stable (t ½ 90 y). The discovery reported in this study most likely to be of certain theoretical and synthetic value.

Effect of substituents on the configurational stability of the stereogenic nitrogen in metal(II) complexes of α‐amino acid Schiff bases

“…Recently, we demonstrated that Ni(II)‐complex 5 (Scheme ) can be successfully used to assess its configurational stability of the stereogenic nitrogen via HPLC assisted kinetic racemization experiments 10a. Our preliminary studies served as a convincing demonstration of the viability of the chosen HPLC‐based approach for working with Ni(II) complexes of AA Schiff bases. In particular, for Ni(II) complex 5 , we reported that the configurational stability of the Ni(II)‐coordinated nitrogen significantly depends on the solvent used for the experiments.…”

“…While reported in the previous work,10a data provided detailed and instructive understanding of the chiral nitrogen configurational stability in relationship to the reaction solvent, the effect of substituents on the nitrogen as well as the coordinating metal remained totally unknown. Thus, drawing inspiration from the success of the previous study,10a we designed a new set of the stereochemical models presented in Scheme .…”

“…Synthesis of compounds 8‐10a‐j was performed similar to general procedures described earlier 9, 10a, 13. Thus, commercially available o ‐amino‐benzophenones 7 were chemo‐selectively acylated using bromoacetyl bromide in acetonitrile to furnish bromo‐amides 8 .…”

New “one‐pot” Pd(II) and Zn(II) complexes of Schiff bases, derivatives of 1‐amino‐1‐deoxy‐d‐sorbitol: Spectroscopic studies and biological and catalytic activities

“…Complexes of Schiff bases play an important role in the detection of various ions, exhibit biological properties, and are widely used as catalysts . Recently, several studies focused on Schiff bases and their complexes, derivatives of natural products, for example, amino sugars, amino acids, and chitosan . Identifying new enantiomerically pure systems is one of the major goals of organic chemistry.…”

“…[4,11,12] Recently, several studies focused on Schiff bases and their complexes, derivatives of natural products, for example, amino sugars, amino acids, and chitosan. [7,[13][14][15][16][17][18][19][20] Identifying new enantiomerically pure systems is one of the major goals of organic chemistry. Although the number of papers published on Schiff bases is increasing every year, they still have a huge potential and are promising ligands of metal complexes.…”