Ancillary Ligand-Controlled Dinitrogen Cleavage and Transformation at Titanium Centers

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Nitrogen (N2) activation and transformation are crucial yet challenging chemical processes.
• Cleaving the strong N2 triple bond, especially using abundant 3d metals like titanium, is a key hurdle in nitrogen fixation research.

Purpose of the Study:

• To investigate ancillary ligand control over N2 activation pathways in titanium complexes.
• To achieve efficient N2 bond cleavage and explore catalytic applications in nitrogen fixation.

Main Methods:

• Synthesis and characterization of PCP-ligated titanium complexes.
• Reductive activation of N2 in the presence of various ancillary ligands (aryloxide, diarylamide, phenyl).
• Computational studies (DFT) to elucidate reaction mechanisms.
• Catalytic testing for N2 silylation.

Main Results:

• Ancillary ligands (aryloxide, diarylamide) promoted N2 cleavage to form dititanium bis(μ-nitrido) complexes.
• The phenyl analogue induced pincer ligand C-P bond activation.
• Computational analysis revealed K+ ion involvement in N2 isomerization and bond rupture.
• Catalytic N2 silylation yielded N(SiMe3)3 with a record turnover number (TON) for Group IV metals.

Conclusions:

• Ligand environment critically influences N2 activation pathways in titanium complexes.
• Heteroatom interactions in the secondary coordination sphere facilitate N2 bond cleavage.
• Developed highly efficient early-metal catalysts for nitrogen fixation, demonstrating significant advancements in the field.