Boron Insertion into the N≡N Bond of a Tungsten Dinitrogen Complex

Area of Science:

• Organometallic chemistry
• Boron chemistry
• Coordination chemistry

Background:

• Tungsten complexes with dinitrogen ligands are important in inorganic synthesis.
• Diborane compounds offer unique reactivity due to boron-boron bonds.

Purpose of the Study:

• To investigate the reaction of diboranes with tungsten dinitrogen complexes.
• To characterize the resulting novel boron-containing tungsten complexes.
• To elucidate the reaction mechanism and subsequent transformations.

Main Methods:

• 1,3-addition reaction of 1,2-diaryl-1,2-dibromodiboranes to trans-[W(N2)2(dppe)2].
• Spectroscopic characterization of intermediates and products.
• Density functional theory (DFT) calculations to study reaction pathways.

Main Results:

• Formation of a 2-aza-1,3-diboraallenylimido complex with a linear B=N=B moiety.
• Spontaneous rearrangement involving B-B and N=N bond cleavage and BAr insertion.
• DFT calculations reveal a mechanism involving cyclic intermediates and adduct formation.
• Reactions with Brønsted acids yield cationic (borylamino)borylimido tungsten complexes.

Conclusions:

• The study demonstrates a novel synthetic route to unique boron-nitrogen-tungsten complexes.
• The observed rearrangement highlights the rich reactivity of diborane-derived ligands.
• The findings expand the scope of organometallic chemistry involving main group elements.