On the Directed Gas Phase Synthesis of the Imidoborane Molecule (HNBH) — An Isoelectronic Molecule of Acetylene (HCCH)

Abstract

The elementary reaction of ground state boron atoms, (B((2)P(j))), with ammonia (NH(3)(X(1)A(1))) was conducted under single collision conditions at a collision energy of 20.5 ± 0.4 kJ mol(-1) in a crossed molecular beams machine. Combined with electronic structure calculations, our experimental results suggested that the reaction was initiated by a barrier-less addition of the boron atom to the nonbonding electron pair of the nitrogen atom forming a weakly bound BNH(3) collision complex. This intermediate underwent a hydrogen shift to a doublet HBNH(2) radical that decomposed via atomic hydrogen loss to at least the imidoborane (HBNH(X(1)Σ(+)) molecule, an isoelectronic species of acetylene (HCCH(X(1)Σ(g)(+))). Our studies are also discussed in light of the isoelectronic C(2)H(3) potential energy surface accessed via the isoelectronic carbon-methyl system.

CCSD(T)‐F12 investigations on HBNH and its isotopologues

“…BNH 2 lies at 162.7 kJ mol −1 higher than HBNH. This value is in good agreement with the recent one of 167 kJ mol −1 , deduced by Zhang et al [1] from CCSD(T)/cc‐pVTZ calculations, and with the one of 173.0 kJ mol −1 , deduced by Rosas‐Garcia and Crawford [13] from CCSD(T) level of theory including CBS limit and core‐valence correlation corrections. Using the same methodology, they obtained that TS is situated 287.7 kJ mol −1 above the equilibrium energy of HBNH.…”

“…Despite its importance in chemistry, few spectroscopic studies can be found related to this molecule. The first real synthesis of imidoborane in gas phase has only been very recently reported by Zhang et al [1] by crossing a supersonic beam of boron atoms with a beam of NH 3 molecules, these compounds initially combining via a Lewis acid‐base reaction. The linear imidoborane molecule is the most stable isomer, whereas C 2v symmetric isomers (BNH 2 ) and (H 2 BN) are predicted to be higher in energy by 167 kJ mol −1 and 323 kJ mol −1 , respectively [1].…”

“…The first real synthesis of imidoborane in gas phase has only been very recently reported by Zhang et al [1] by crossing a supersonic beam of boron atoms with a beam of NH 3 molecules, these compounds initially combining via a Lewis acid‐base reaction. The linear imidoborane molecule is the most stable isomer, whereas C 2v symmetric isomers (BNH 2 ) and (H 2 BN) are predicted to be higher in energy by 167 kJ mol −1 and 323 kJ mol −1 , respectively [1]. Himmel [2] reviewed some aspects of the variety of structures and of the reactivity of small molecules containing subvalent group 13 elements among which HBNH.…”

“…Theoretically, several investigations have been performed on the imidoborane molecule, especially on its structure, harmonic wavenumbers, and reactivity [1, 7–12]. In 1972, Baird and Datta [7] predicted the existence of imidoborane using SCF‐LCAO‐MO calculations.…”

B═N Bond Cleavage and BN Ring Expansion at the Surface of Boron Nitride Nanotubes by Iminoborane

“…Although structure and properties of iminoboranes have been an active field of both theoretical and experimental research for several years 4−13 only recently has the HBNH molecule been synthesized in the gas phase. 14 R−BN−R′ readily oligomerizes to stable cyclic (RBNR′) n (n = 2, 3, and 4) where substituent groups play a significant role in the factor n. 3 In these cyclization processes, HBNH changes from sp hybridization to sp 2 cyclic products, i.e, [2+2] cycloaddition to form (RBNR′) 2 . This reactivity feature raises some questions about the reaction between HBNH and boron nitride nanotubes (BNNTs) where B and N atoms are pseudo sp 2 hybridized (because of strain) and tubes contain both Lewis acid (B-sites) and Lewis base (N-sites) centers.…”