Linear End-On Coordination Modes of CO₂.

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Carbon Dioxide Fixation

Background:

• Vanadium aryloxide complexes with tetradentate (ONNO) ligands are known to interact with small molecules.
• Understanding carbon dioxide (CO2) coordination modes is crucial for developing catalytic fixation strategies.
• Previous studies have identified limited coordination geometries for CO2 with metal complexes.

Purpose of the Study:

• To investigate novel coordination modes of carbon dioxide (CO2) with vanadium aryloxide complexes.
• To explore the reactivity of vanadium complexes with CO2 under different oxidation states and conditions.
• To provide evidence for new CO2 binding geometries, including bridging end-on coordination.

Main Methods:

• Synthesis and characterization of vanadium aryloxide complexes featuring a tetradentate (ONNO) ligand system.
• Reaction of divalent (ONNO)V(II) with CO2 under specific conditions leading to CO2 deoxygenation and fixation.
• Reduction of trivalent (ONNO)V(III) complexes followed by reaction with CO2 to yield dinuclear species.

Main Results:

• Discovery of the second known case of linear end-on carbon dioxide (CO2) coordination to a vanadium complex.
• Evidence for an unprecedented bridging end-on coordination mode of CO2 in a dinuclear vanadium complex.
• Observation of CO2 fixation via a deoxygenation pathway and subsequent H-atom abstraction in a trivalent vanadium complex.

Conclusions:

• Vanadium aryloxide complexes can stabilize unique and reactive carbon dioxide (CO2) coordination modes.
• The findings expand the known coordination chemistry of CO2, particularly in bridging end-on configurations.
• This research contributes to the fundamental understanding of CO2 activation and fixation relevant to catalysis.