DFT-based characterization of double β-B-Bagostic interaction in model Ti-borane complexes

Simultaneous activation of two intramolecular B-H bonds in Ti-borane complexes, designated as double β-B-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-NH2BH3 [L=Cl-, M=H2O, y+z=3-6] compounds have been considered to investigate the electronic and structural properties of double β-B-agostic interaction. Our analysis infers that the strength, pattern, and symmetricity of the B-H bond activation depend on each tuning parameter mentioned above; in extreme cases, a few complexes show single B-H activation. It has been noticed that the extent of activation of B-H bonds has a proportional relationship with B-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-B-agostic interaction. Overall, the concept of double β-B-agostic interactions encourages the researcher to study novel catalytic activities related to metal-borane complexes through more than one B-H bonds activation.