Cationic Niobium-Sandwich and Piano-Stool Complexes

Area of Science:

• Organometallic Chemistry
• Niobium Chemistry
• Coordination Chemistry

Background:

• Organometallic niobium complexes are crucial in catalysis and materials science.
• Stabilization of low-valent niobium complexes often requires weakly coordinating anions.
• Synthesis of homoleptic and heteroleptic niobium cations presents unique challenges.

Purpose of the Study:

• To synthesize and characterize novel homoleptic bis(arene) niobium cations and heteroleptic arene-carbonyl niobium cations.
• To investigate the stabilization of these niobium complexes using weakly coordinating anions.
• To explore the synthetic routes for these organometallic niobium compounds.

Main Methods:

• Synthesis of niobium complexes starting from neutral Nb(arene)2 or [NEt4][M(CO)6].
• Stabilization using weakly coordinating anions like [Al(OR^F)4]- or [F{Al(OR^F)3}2]-.
• Characterization through single crystal X-ray diffraction, vibrational spectroscopy, and NMR spectroscopy.
• Density Functional Theory (DFT) calculations to support experimental findings.

Main Results:

• Successful synthesis of 16-valence electron homoleptic bis(arene) niobium cations ([Nb(arene)2]+).
• Successful synthesis of 18-valence electron heteroleptic arene-carbonyl niobium cations ([(CO)Nb(arene)2]+ and [(arene)M(CO)4]+).
• Demonstrated effectiveness of weakly coordinating anions for stabilizing these niobium complexes.
• Investigation of the scope and limitations of two distinct synthetic pathways.

Conclusions:

• The study successfully synthesized and characterized a range of novel niobium complexes with varying electronic configurations.
• Weakly coordinating anions are effective in stabilizing reactive niobium cations.
• The explored synthetic routes provide valuable insights into the preparation of organometallic niobium compounds.