Quantum study of the ground state of a series of unsaturated boron–nitrogen compounds by the MNDO method. I. Geometries and stabilities

Abstract

A MNDO study of molecular geometries, enthalpies, formation, atomization, bond separation, and hydrogenation of a series of unsaturated boron-nitrogen compounds, linear with two and three members and cyclic with three, four, five, and six members are presented. For all these molecules, MNDO calculations are in excellent agreement with available ab initio calculations or experimental data. The high rotational barrier in aminoborane HlBNH2, 30.6 kcal/mol, and the length of bond in iminoborane HBNH, 1.1 83 A, imply strong double and triple BN bond character in these two molecules. In the odd membered heterocycles, examination of the molecular geometries and energies of equilibrium states shows that in all cases, the stability of the compounds grows with the number of boron atoms and decreases with that of the nitrogen atoms. Moreover, compared study of the two BN-fulvenes with their homologous hydrocarbon shows that only BN (BB)-fulvene has a polyenic structure similar to that of fulvene.

MNDO calculations on borazine derivatives. The substitution of one [HNBH] fragment for one [HCCH] fragment in benzene to form the azaborines and the nature of the cyclotrimer of the 1,2‐isomer

“…Our results for benzene and borazine are identical with those of Dewar and co-workers [24,25]. However, in the report of Maouche and Gayoso [26], a heat of forma- tion of -130.8 kcal/mol was calculated for borazine, which is about 1% less negative than that calculated in our study.5…”

“…Thus, we thought that MNDO would be an appropriate probe of the properties of the azaborines. Further, Maouche and Gayoso [26] report the MNDO study of a series of linear and cyclic unsaturated boron-nitrogen compounds and concluded that Chart II…”

“…For the formal cyclotrimers of benzene and 1,2-azaborine, the first row lists the ring atom-ring atom bond indices for the central ring, and the second row lists the bond indices for one fused ring. index of 1 26. (2)] indicate a lack of bond localization and, in fact, the presence of unsymmetrical delocalization, if translated into a valence bond picture.…”

MNDO calculations on boron–nitrogen derivatives of nonbenzenoid aromatics: I. The two fully boron–nitrogen‐alternating isomers of “inorganic azulene”

“…The PAPBAZ isomers 1 and 2 have apparently not been studied experimentally, and only one computational report [9] mentions these molecules. However, because the MNDO method has been shown [17, [25][26][27][28]] to be a reliable indicator of the ground-state properties of boron-nitrogen-containing molecules, there exists a solid basis upon which to establish the structures of these molecules. The PAPBAZ isomers 1 and 2 are calculated to be planar molecules, possibly containing n-systems at least as delocalized as in borazine.…”

Triplet potential energy surface for BH2N: A DFT study

“…The structures, stability, and reactivity of iminoborane were reviewed by Paetzold [5]. In the past three decades, iminoborane aroused considerably interest in several experimental and some theoretical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”