Dibora[2]ferrocenophane: A Carbene-Stabilized Diborene in a Strained cis-Configuration

Area of Science:

• Organometallic Chemistry
• Boron Chemistry
• Metallocene Chemistry

Background:

• Unsaturated bridges in strained ansa metallocenes are typically limited to carbon-carbon double bonds.
• The synthesis of ferrocenophanes with unsaturated bridges, especially those involving heteroatoms, is challenging.

Purpose of the Study:

• To synthesize and characterize a strained ferrocenophane featuring an unsaturated two-boron bridge.
• To investigate the influence of this novel structural motif on the compound's optical and electrochemical properties.
• To explore the initial reactivity of the dibora[2]ferrocenophane.

Main Methods:

• Synthesis via reduction of a carbene-stabilized 1,1'-bis(dihaloboryl)ferrocene.
• Characterization using spectroscopic (e.g., NMR, IR) and electrochemical measurements.
• Theoretical analysis using density functional theory (DFT) calculations.

Main Results:

• Successful synthesis and isolation of a strained ferrocenophane with a two-boron unsaturated bridge, isoelectronic to a C=C double bond.
• The strained cis configuration significantly impacts the optical and electrochemical properties of the carbene-stabilized diborene unit.
• The dibora[2]ferrocenophane exhibits susceptibility to boron-boron double bond cleavage reactions.

Conclusions:

• The study presents the first example of a strained ferrocenophane with an unsaturated two-boron bridge.
• The findings provide insights into the electronic and structural effects of incorporating strained unsaturated boron bridges in metallocenes.
• The reactivity studies highlight potential pathways for further functionalization or decomposition of such compounds.