Base-stabilized diborenes: selective generation and η2 side-on coordination to silver(I)

Area of Science:

• Organometallic Chemistry
• Boron Chemistry

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands in coordination chemistry.
• Boron-nitrogen compounds are of increasing interest due to their unique bonding.

Purpose of the Study:

• To synthesize and characterize novel diborane compounds stabilized by NHC ligands.
• To investigate the electronic structure and bonding of these diborenes.
• To explore the reactivity of diborenes with metal precursors.

Main Methods:

• Reductive coupling of designed monoborane precursors.
• Synthesis of N-heterocyclic carbene stabilized diborenes.
• Spectroscopic (NMR, UV-Vis) and X-ray crystallographic characterization.
• Density Functional Theory (DFT) calculations.
• Reaction with silver(I) chloride (AgCl).

Main Results:

• Convenient access to dark red diborenes stabilized by NHC ligands.
• Experimental and theoretical evidence for B-B multiple bonding within the diborenes.
• Formation of a unique Ag(I) complex exhibiting an unprecedented η(2) coordination mode, analogous to olefin coordination.

Conclusions:

• NHC-stabilized diborenes are accessible and possess intriguing B-B multiple bonding.
• The observed η(2) coordination of diborenes to silver highlights novel reactivity and bonding modes in boron chemistry.