Ligand‐Controlled CO2 Activation Mediated by Cationic Titanium Hydride Complexes, [LTiH]+ (L=Cp2, O)

CO₂ activation mediated by LTiH]⁺ (L=Cp₂, O) is observed in the gas phase at room temperature using electrospray‐ionization mass spectrometry, and reaction details are derived from traveling wave ion‐mobility mass spectrometry. Wheresas oxygen‐atom transfer prevails in the reaction of the oxide complex OTiH]⁺ with CO₂, generating OTi(OH)]⁺ under the elimination of CO, insertion of CO₂ into the metal–hydrogen bond of the cyclopentadienyl complex, Cp₂TiH]⁺, gives rise to the formate complex Cp₂Ti(O₂CH)]⁺. DFT‐based methods were employed to understand how the ligand controls the observed variation in reactivity toward CO₂. Insertion of CO₂ into the Ti?H bond constitutes the initial step for the reaction of both Cp₂TiH]⁺ and OTiH]⁺, thus generating formate complexes as intermediates. In contrast to Cp₂Ti(O₂CH)]⁺ which is kinetically stable, facile decarbonylation of OTi(O₂CH)]⁺ results in the hydroxo complex OTi(OH)]⁺. The longer lifetime of Cp₂Ti(O₂CH)]⁺ allows for secondary reactions with background water, as a result of which, Cp₂Ti(OH)]⁺ is formed. Further, computational studies reveal a good linear correlation between the hydride affinity of LTi]²⁺ and the barrier for CO₂ insertion into various LTiH]⁺ complexes. Understanding the intrinsic ligand effects may provide insight into the selective activation of CO₂.