Syntheses and structures of three chiral complexes derived from nucleophilic addition of L-proline to di-2-pyridyl ketone

Abstract

In the presence of nickel acetate, a chiral ligand, (S)-Hdphp ((S)-N-[di(2-pyridyl)-hydroxy-methyl]-proline), was synthesized in situ by nucleophilic addition of L-proline to di-2-pyridyl ketone. Based on this ligand, three chiral mononuclear complexes, {Ni[(S)-dphp](DMF)(H₂O)}(ClO₄) (1), {Ni[(S)-dphp](H₂O)₂}(ClO₄)(H₂O)_1.5 (2), and {Ni[(S)-dphp](SCN)(H₂O)} (3), have been obtained and characterized by single-crystal X-ray diffraction, elemental analyses, and infrared spectra. By virtue of charge-assisted O–H ··· O hydrogen-bonding interactions, all the complexes possess double chain structures. The double chains were connected into 2-D networks via π ··· π stacking and CH ··· π interactions in 1. For 2, O–H ··· O hydrogen-bonding interactions between free water molecules and other oxygens as well as π ··· π stacking and CH ··· π interactions extend the chains into a 3-D network. Complex 3 exhibits 3-D structure via O–H ··· S interactions.

Keywords:

• Nucleophilic additions
• Chiral
• Hydrogen-bonding interactions

Acknowledgments

The authors thank X.T. Wu and T.L. Sheng for their help. This research is supported by financial support from Henan University, the National Science Foundation of the Education Department of Henan Province (2011A150004), and the State Key Laboratory of Structural Chemistry (20110008).