Synthesis and characterization of new Ni(II) complexes with S,N-heterocycle ligands: influence of the steric strain of ligands on coordination

The complexes [NiCl2(PyTn)2] · 2H2O (1), [Ni(H2O)2(PyTn)2](NO3)2 (2), [Ni(H2O)2(PzTz)2]Cl2 (3) and [Ni(H2O)2(PzTz)2](NO3)2 (4) [PyTn = 2-(1-pyrazolyl)-2-thiazoline; PzTz = 2-(1-pyrazolyl)-1,3-thiazine] have been prepared and characterized by elemental analysis, electronic spectroscopy, IR spectroscopy and single crystal X-ray diffraction to determine if the size of the S,N-heterocycle influences coordination to Ni(II). The four complexes are six coordinate as a distorted octahedron. The disposition of chlorides and water is trans in 1 and 2, whereas 3 and 4 are cis, as a consequence of the steric strain induced by the larger S,N-ring.