Coordination-induced bond weakening and small molecule activation by low-valent titanium complexes

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Coordination to low valent metal complexes, particularly titanium, facilitates the activation of small molecules through M⋯X-H interactions.
• This process weakens X-H bonds (where X = O, N, B, Si, etc.), enabling reactions under mild conditions.

Purpose of the Study:

• To provide an overview of coordination-induced bond activation of small molecules by low valent titanium complexes.
• To highlight the specific applications of this methodology in nitrogen fixation.

Main Methods:

• Review of literature on low valent titanium chemistry and small molecule activation.
• Analysis of electronic structure changes upon coordination, focusing on electron redistribution between metal and ligand orbitals.
• Examination of bond cleavage mechanisms (X-H and N-N) facilitated by titanium complexes.

Main Results:

• Coordination of small molecules (water, amides, silanes, boranes, dinitrogen) to Ti(II) or Ti(III) complexes leads to significant bond weakening.
• Synergetic electron redistribution between titanium and ligand orbitals is key to facile bond cleavage.
• Demonstrated utility in nitrogen fixation, showcasing the potential for N-N bond activation.

Conclusions:

• Low valent titanium complexes offer a powerful platform for coordination-induced bond activation.
• Future directions include developing Ti-based proton-coupled electron transfer (PCET) systems and photocatalytic nitrogen reduction.
• Tailoring titanium complexes is crucial for optimizing bond activation efficiency.