Linear End‐On Coordination Modes of CO₂

Abstract

The second case of linear end-on and evidence for an unprecedented bridging end-on coordination mode of CO 2 have been discovered for vanadium aryloxide complexes of the tetradentate ligand system (ONNO) 2À (ONNO = 2,4-Me 2-2-(OH) C 6 H 2 CH 2 ] 2 N(CH 2) 2 NMe 2). The reaction of divalent (ONNO)V II (TMEDA) with CO 2 and under the appropriate reaction conditions affords the trivalent (ONNO)V III (OH)(h 1-CO 2)r esulting from an intermediate CO 2 deoxygenation pathway followed by H-atom abstraction from the aromatic solvent, and CO 2 fixation. In contrast, the reduction of trivalent (ONNO)V III Cl(THF) with K, followed by exposure to CO 2 in ethereal solvent, afforded the dinuclear [(ONNO)V II ] 2 (m , h 1-CO 2).

Recent Advances in the Chemistry of Metal Carbamates

“…The former goal is challenging for a variety of reactions, and a wide number of metal catalysts have been proposed to access valuable organic compounds and materials via CO 2 fixation strategies, which, however, require harsh conditions (high temperature and CO 2 pressure) in several cases [ 14 , 15 ]. It is worthy to note that, differently to other small molecules such as its relative carbon monoxide, carbon dioxide is a “bad” ligand for transition metals; therefore, examples of simple coordination compounds are relatively rare [ 16 , 17 , 18 , 19 , 20 , 21 ] and, accordingly, metal catalysts working in CO 2 activation routes usually exert their action without the intermediacy of metal-CO 2 adducts. The “weak point” in the apparently unscratchable robustness of carbon dioxide is the susceptibility to nucleophilic attacks at the carbon atom [ 22 , 23 , 24 ].…”