Effect of the benzyl groups on the binding of H2 by three-coordinated Ti complexes

TL;DR

This study uses first-principles calculations to clarify how benzyl groups influence H2 binding on titanium complexes, challenging previous experimental interpretations and providing insights into adsorption mechanisms.

Contribution

It reveals that benzyl-released Ti(III) complexes can adsorb H2 molecules via Kubas interaction, differing from prior experimental assumptions about Ti(III) complexes.

Findings

Ti(III) complex cannot adsorb H2 via Kubas interaction

Benzyl-released Ti(III) complex adsorbs up to two H2 molecules

Calculated adsorption energies and occupation numbers match experimental data

Abstract

Using first-principles calculations, we investigate the adsorption of H2 molecules on a three-coordinated benzyl-decorated titanium complex suggested in a recent experiment [Hamaed et al., J. Am. Chem. Soc. 130, 6992 (2008)]. Unlike the interpretation of the experimental results that the Ti(III) complex can bind five H2 molecules via the Kubas interaction, the Ti(III) complex cannot adsorb H2 molecules via the Kubas interaction. In contrast, a benzyl-released Ti(III) complex can adsorb up to two H2 molecules with a binding energy of ~0.25 eV/H2 via the Kubas interaction, in good agreement with the measurement of ~0.2 eV. The calculated occupation number of H2 molecules at 25 oC and -78 oC under 60 atm is 0.9 and 1.9, respectively, in good agreement with the measurement of 1.1 and 2.4 near the conditions, respectively. Our results suggest that the Ti complex in experiment might be a benzyl-released form.