Iron(II) Complexes of P₃ -Chain Ligands: Structural Diversity

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Phosphorus Chemistry

Background:

• Iron complexes with phosphorus-based ligands are crucial in catalysis and materials science.
• Understanding ligand binding modes is key to controlling complex reactivity and properties.
• Triphosphane ligands offer diverse coordination possibilities due to their unique P-P-P backbone.

Purpose of the Study:

• To synthesize and characterize novel iron(II) complexes featuring R2P-P-PR2 triphosphane ligands.
• To investigate the influence of substituent size (R=tBu, iPr) on ligand binding modes and complex formation.
• To explore the formation of different isomers and chelate structures in these iron complexes.

Main Methods:

• Metathesis reactions for the synthesis of iron(II)-triphosphane complexes.
• Nuclear Magnetic Resonance (NMR) spectroscopy for solution-state characterization.
• Single-crystal X-ray diffraction for solid-state structural determination.
• Density Functional Theory (DFT) calculations to support synthetic findings.

Main Results:

• Synthesis of iron(II) complexes with R2P-P-PR2 ligands.
• Formation of two isomers with R=tBu: one ylidic (terminal P binds to Fe) and one with central P bound to Fe.
• Chelate complex formation with R=iPr (both terminal P atoms bind to Fe).
• Preference for the ylidic structure when using mixed-substituted triphosphanes.

Conclusions:

• The size of substituents on the triphosphane ligand significantly dictates the binding mode to the iron(II) center.
• Steric effects control the formation of ylidic, central-binding, or chelate isomers.
• This study provides insights into the rational design of iron complexes with tailored ligand coordination.