Density Functional Theory Studies On The Electronic Structure And Characteristics Of Boranes And Their Derivatives

A large number of boranes and their derivatives have been synthesized since 1912 after Alfred Stock synthesized a series of boranes such as B2H6, B4H10, B5H9 and B6H10. As electron-deficient compounds, the features of special covalent bonds of borane have led to increase research interest of Chemists, a lot of studies on molecular structures and characters of chemical bond of boranes and their derivatives have been reported. However, to our knowledge, no systemic computational study on the nature of their multi-center covalent bond has been reported.To obtain insight into the characteristics of electron-deficient covalent bonds, in this paper, the molecular and electronic structures of B2H6, B2H5Br, C2H10B2, C4H14B2, B2H7N, C2H11B2N, B3H7CO, B3H7NCS—, B3H7NCSe—, B3H7NCBH3—, B3H6Cl2—, B5H9, B6H8S2CH2, B8H12, B10H14, B4H10, B9H15, B10H16 and B4H6C2H2 have been studied at the B3LYP/6-31++G (d, p) theoretical level by employing the Gaussian03 program. The Wiberg bond indexes (order) of these compounds computed on the basis of their full optimized geometries have been used to analyze the characteristics of electron-deficient covalent bonds and their molecular stabilities. The vertical detachment energies and vertical attachment energies of B2H6, B4H10, B5H9, B8H12, B9H15, B10H16, B2H4C2H6, B2H2C4H12, B2H5NH2, B2H5NC2H6 and B3H7CO were also computed by experimental calibrated theoretical method B3LYP/DZP++ so as to understand their redox features. All of theoretical results indicate:(1) The Wiberg bond orders of all molecule calculated by B3LYP/6-31++G(d, p) method are significant larger than that computed from two-center-two-electron canonical bond;(2) The analysis of molecular orbital reveals the presence of multi-center bond in molecules of boranes and their derivatives;(3) The cage structures of boranes and their derivatives should be attributable to their feature of electron-deficiency; these molecular structures are in favor of the formations of multi-center...