Synthesis, Ni(II) Schiff base complexation and structural analysis of fluorinated analogs of the ligand (S)-2-[N-(N′-benzylprolyl)amino]benzophenone (BPB)

Herein we report the first X-ray crystal structure of the well-known (S)-l-ala-Ni-BPB complex (1) and compare this with the X-ray crystal structures obtained for two novel fluorinated (S)-l-ala-Ni-BPB complexes (8 and 12) that contain either an S- or R-fluorine atom on the proline ring of the BPB ligand. The preparation of complexes 8 and 12 has been enabled by the synthesis of two new fluorinated BPB ligands (7 and 11). In this work we looked to observe the structural effects that the introduction of a single fluorine atom had on the known complex 1. Arising from this, we highlight a novel fluorine–nickel interaction that on the basis of DFT calculations appears to provide additional stabilization to one of the complexes prepared ((S)-l-ala-Ni-BPB complex 8).