High-spin iron(III) complexes: structural, spectroscopic, and photochemical studies

Abstract

Reaction of FeCl₃ with one equivalent of acac (acac = pentane-2,4-dionate) and KTp^Me2 (Tp^Me2 = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate) yielded Tp^Me2Fe(acac)Cl (3), which upon reaction with methanolic solution of sodium azide resulted in the formation of a six coordinate compound Tp^Me2Fe(acac)N₃ (4) with a single azide. When the reaction of FeCl₃ and KTp^Me2 was performed with two equivalents of sodium azide and one equivalent of 3,5-dimethylpyrazole (Pz^Me2H), a six coordinate cis azide compound [Tp^Me2Fe(Pz^Me2H)(N₃)₂] (5) was obtained. These compounds were characterized by spectroscopic methods and single crystal X-ray crystallography. Electrochemical studies of 5 show that it can be irreversibly reduced at relatively lower potential than 4. The photolysis of 5 was performed at 77 K at different wavelengths (480, 419, and 330 nm) showing that 5 was photoreduced to a high-spin Fe(II) species instead of photooxidized to Fe(V).

Keywords:

• Mononuclear iron complex
• Pyrazolylborate
• Azide ligand
• Crystal structure

Acknowledgements

We are grateful to the DST, New Delhi for financial support. UPS is very thankful to the Alexander von Humbold Foundation for supporting the visit to Max-Planck-Institute für Bioanorganische Chemie, Mülheim, Germany and Prof. K. Wieghardt for providing laboratory space and also for his continuous encouragement. UPS is also thankful to Bernd Mienert for Mössbauer measurement at Max-Planck-Institute für Bioanorganische Chemie, Mülheim, Germany.