Structural and spectroscopic comparison of five-coordinate cobalt(II) and nickel(II) thiolato complexes with the related four-coordinate complexes

Five-coordinate thiolato complexes, [L1M(SMeIm)] (M = Co and Ni) (L1 = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion and HSMeIm = 2-mercapto-1-methylimidazole), were synthesized. These complexes were compared with the corresponding Cu(II) and Zn(II) complexes with the same ligands and were also compared with the related four-coordinate complexes [L1M(SC6F5)] (HSC6F5 = pentafluorobenzenthiol). All the complexes were characterized by X-ray crystallography and UV–Vis absorption, IR, 1H NMR, and other spectroscopic techniques. All five-coordinate thiolato complexes, [L1M(SMeIm)] (M = Co, Ni, and Cu), form a distorted square pyramidal structure with a high spin state, and only [L1Zn(SMeIm)] takes a four-coordinate structure with a distorted tetrahedral configuration. The N21–M–S bond angles of the obtained five-coordinate complexes were proportional to the corresponding d value, which comes from between the equatorial basal plane with N4S ligand donor sets and metal ion. These observations and M–S bond distances affect on UV–Vis and far-IR spectral behavior.