Transition metal complexes with thiosemicarbazide-based ligands. Part LIV. Nickel(II) complexes with pyridoxal semi- (PLSC) and thiosemicarbazone (PLTSC). Crystal and molecular structure of [Ni(PLSC)(H2O)3](NO3)2 and [Ni(PLTSC-H)py]NO3

This paper describes the synthesis of the first Ni(II) complexes with pyridoxal semicarbazone (PLSC), viz. Ni(PLSC)Cl₂ · 3.5H₂O (1), Ni(PLSC)(H₂O)₃](NO₃)₂ (2), Ni(PLSC)(NCS)₂ · 4H₂O (3), Ni(PLSC-2H)NH₃] · 1.5H₂O (4), as well as two new complexes with pyridoxal thiosemicarbazone (PLTSC), Ni(PLTSC-H)py]NO₃ (5) and Ni(PLTSC-H)NCS] (6). Complexes 1–3 are paramagnetic and have most probably an octahedral structure, for complex 2 this was proved by X-ray diffraction analysis. In contrast, complexes 4–6 are diamagnetic and have a square-planar structure, and in the case of complex 5 this was also confirmed by X-ray structural analysis. In all cases the Schiff bases are coordinated as tridentate ligands with an ONX (X = O, PLSC; X = S, PLTSC) set of donor atoms. With the complexes involving the neutral form of PLSC and the monoanionic form of PLTSC, the PL moiety is in the form of a zwitterion. In addition to the above-mentioned techniques, all the complexes were characterized by measuring their molar conductivities, UV–Vis and partial IR spectra.