Cobalt(II) complexes of creatinine

Summary

Cobalt(II) complexes of creatinine [Co(creat)₂X₂] (X = Cl, Br, I or NCS) and [Co(creat)₂X₂(H₂O)₂] (X = HCO₂, HOCH₂CO₂ or CNCH₂CO₂) have been prepared. Their i.r. spectra show an increase in ν(NH) of the cyclic secondary amine group, compared to free ligand (3300 cm⁻¹), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d⁷ configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co₃O₄. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.