Bulky 1,1'-bisphosphanoferrocenes and their coordination behaviour towards Cu(i)

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• Development of novel phosphine ligands is crucial for advancing coordination chemistry and catalysis.
• Bulky ligands can influence coordination modes and catalytic activity.
• Iron-based diphosphane ligands offer unique electronic and steric properties.

Purpose of the Study:

• To synthesize and characterize novel bulky mesityl-substituted dppf-analogues.
• To explore the coordination behavior of these ligands with copper(I) ions.
• To evaluate the catalytic efficiency of the resulting copper(I) complexes in CO2 fixation.

Main Methods:

• Synthesis of iron diphosphane ligands: Fe(C5H4PMes2)2 (1) and Fe(C5H4PMes2)(C5H4PPh2) (3).
• Characterization using heteronuclear NMR spectroscopy (1J P-Se coupling), cyclic voltammetry, and DFT calculations.
• Preparation and structural analysis of mono- and dinuclear copper(I) complexes with various counter anions (Br-, I-, BF4-).
• Evaluation of catalytic activity in CO2 fixation with terminal alkynes.

Main Results:

• Two bulky mesityl-substituted dppf-analogues were successfully synthesized.
• Unprecedented double bridging complexation modes were observed for the very bulky ligand 1 with copper(I).
• Copper(I) complexes with ligand 3 demonstrated higher catalytic efficiency in CO2 fixation compared to ligand 1.
• DFT calculations supported the observed catalytic trends.

Conclusions:

• Novel bulky diphosphane ligands exhibit unique coordination behavior with copper(I).
• The steric bulk of the ligand significantly influences complex structure and catalytic performance.
• These copper(I) complexes are effective catalysts for CO2 fixation, with ligand 3 showing superior activity.