DFT-based characterization of double β-agostic interaction in model Ti-borane and Ti-alane complexes

Simultaneous activation of two intramolecular X-H (X=B, Al) bonds in Ti-borane and Ti-alane complexes, designated as double β-agostic interaction, has been investigated using state-of-the-art DFT techniques and further tuned by coordination number, systematic substitution, and conformational changes. A series of (L)y(M)zTi-NH2XH3 [L=Cl-, M=H2O, y+z=3-6] compounds has been considered to investigate the electronic and structural properties of double β-agostic interaction. Our analysis infers that the strength, pattern, and symmetricity of the X-H activation depend on each tuning parameter mentioned above; in extreme cases, a few complexes show single X-H activation. It has been noticed that the extent of activation of X-H bonds has a proportional relationship with X-H bond distance and an inversely proportional relationship with Ti-H bond distance, which is further confirmed through QTAIM analysis. The formation of partial covalent character between Ti and H centers illustrates the impact of metal on the generation of double β-agostic interaction. Overall, the concept of double β-agostic interactions encourages the researcher to study novel catalytic activities related to metal-borane/alane complex through more than one X-H bonds activation.