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, Cp2 TiH , gives rise to the formate complex Cp2 Ti(O2 CH) . 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 Cp2 TiH and OTiH , thus generating formate complexes as intermediates. In contrast to Cp2 Ti(O2 CH) which is kinetically stable, facile decarbonylation of OTi(O2 CH) results in the hydroxo complex OTi(OH) . The longer lifetime of Cp2 Ti(O2 CH) allows for secondary reactions with background water, as a result of which, Cp2 Ti(OH) is formed. Further, computational studies reveal a good linear correlation between the hydride affinity of LTi and the barrier for CO2 insertion into various LTiH complexes. Understanding the intrinsic ligand effects may provide insight into the selective activation of CO2 .