Iron(II) complexes of dimethyltriazacyclophane

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Supramolecular Chemistry

Background:

• Triazacyclophane ligands are versatile building blocks in coordination chemistry.
• Previous studies suggested chelating coordination modes for these ligands.

Purpose of the Study:

• To synthesize and characterize novel iron(II) complexes with a specific triazacyclophane ligand.
• To investigate the coordination behavior and structural properties of these iron complexes.
• To compare experimental findings with theoretical predictions.

Main Methods:

• Synthesis of dimeric and monomeric iron(II) complexes.
• Crystallographic analysis of the complexes.
• Density functional theory (DFT) calculations.

Main Results:

• Formation of a dimeric iron(II) complex [Fe(L1)4] and a monomeric solvated complex [Fe(L1)2(THF)2].
• The triazacyclophane ligand adopts a saddle conformation, not a bowl-shaped conformer.
• Ligands coordinate in monodentate or η2-chelating fashions, differing from DFT predictions.
• DFT calculations indicate significant positive charges on iron atoms and no direct Fe-Fe bonding in the dimer.

Conclusions:

• The study reveals unexpected coordination modes of the triazacyclophane ligand in iron(II) complexes.
• Experimental structural data contradict previous DFT-based proposals for chelating coordination.
• The findings provide new insights into the coordination chemistry of triazacyclophanes with iron.