Two new Ni(II) Schiff base complexes: X-ray absolute structure determination, synthesis of a 15N-labelled complex and full assignment of its 1H NMR and 13C NMR spectra

The Ni(II) complex of the Schiff base of (S)-N-(2-benzoyl-4-chlorophenyl)-1-benzylpyrrolidine-2-carboxamide and glycine (1) [GKCl] and the hemihydrate of the Ni(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and 2-aminoisobutiric acid (2) [Me2GK] were prepared and their absolute structures determined. The conformations of the complexes and their hydrogen bonding are discussed in detail. In complex 2, the repulsion between the benzyl group and an equatorial methyl group should affect the conformation of the benzyl group, distribution of the π-electron density in this group and distortion of the internal coordination sphere, while for complex 1, only minor conformational changes were expected. 1H and 13C NMR data for the 15N-labelled complex 2 were acquired and fully assigned in order to study the influence of π-electron density of the benzyl group to the long-range 13C–15N and 13C–13C spin–spin interactions.

Graphical abstractThe Ni(II) complex of the Schiff base of (S)-N-(2-benzoyl-4-chlorophenyl)-1-benzylpyrrolidine-2-carboxamide and glycine (1) and the hemihydrate of the Ni(II) complex of the Schiff base of (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide and 2-aminoisobutiric acid (2) were prepared and characterized by X-ray diffraction and 1H and 13C NMR.Figure optionsDownload full-size imageDownload as PowerPoint slide