Density functional theory studies on structural isomers and bonding of catecholborane adducts of Group 5 metallocene (Nb, Ta) hydride complexes

Density functional theory calculations at the Becke3LYP level have been performed to study structural isomers of borane adducts of Cp2M(H) (M=Nb, Ta). Results of calculations show that O- and N-substituted borane adducts can have various structural isomers including boryl, hydridoborate and σ-complex structures. H-, alkyl- and Cl-substituted borane adducts are found to adopt hydridoborate structures. The structural feature is closely related to how the electron-deficient boron center is electronically saturated.