Linear End-On Coordination Modes of CO₂

The second case of linear end-on and evidence for an unprecedented bridging end-on coordination mode of CO₂ have been discovered for vanadium aryloxide complexes of the tetradentate ligand system (ONNO)^2- (ONNO=2,4-Me₂ -2-(OH) C₆ H₂ CH₂ ]₂ N(CH₂ )₂ NMe₂ ). The reaction of divalent (ONNO)V^II (TMEDA) with CO₂ and under the appropriate reaction conditions affords the trivalent (ONNO)V^III (OH)(η¹ -CO₂ ) resulting from an intermediate CO₂ deoxygenation pathway followed by H-atom abstraction from the aromatic solvent, and CO₂ fixation. In contrast, the reduction of trivalent (ONNO)V^III Cl(THF) with K, followed by exposure to CO₂ in ethereal solvent, afforded the dinuclear [(ONNO)V^II ]₂ (μ_, η¹ -CO₂ ).