Influence of steric strain of S,N-heterocycles derivative ligands on the coordination geometry in cadmium(II) nitrato complexes

The new ligands 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline (DMPyTn) and 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline (DPhPyTn) have been synthesized and characterized, and six cadmium(II) nitrato complexes with these two ligands and four other pyrazole/S,N-heterocyclic derivative ligands with different steric features, previously reported, have been prepared and structurally characterized by means of elemental analysis, single crystal X-ray diffraction and IR spectra, with the objective of determining the role played by the steric strains of the ligands on the metal ion coordination index and geometry. The effect of two factors has been analyzed: the bulk of the pyrazole ring substituents and the size of the S,N-heterocycle. The data indicate that there is a clear influence of the size of the organic ligands on the coordination environment of the Cd(II) ion.

Graphical abstractSix cadmium(II) nitrato complexes with pyrazole/S,N-heterocycle derivative ligands with different steric features have been prepared and structurally characterized. The organic ligands which are more voluminous induce a lower coordination index and a higher distortion of the coordination polyhedron in the complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two novel pyrazole/thiazoline derivative chelates are synthesized. ► Six Cd(II) complexes with pyrazole/S,N-heterocycle derivative ligands are prepared. ► Several coordination indexes and geometries have been found for the complexes. ► The influence of the size of the ligands in the coordination geometry is studied.