Triplet potential energy surface for BH₂N: A DFT study

The triplet potential energy surfaces (PES) for the isomerization and dissociation reactions of BH₂N isomers was investigated using the DFT/B3LYP method of theory. Thirteen BH₂N isomer species and two dissociated products were identified, in which five isomerization reactions and four dissociation pathways were found. On the triplet PES, the nonplanar trans-iminoborane (1) can isomerize to the lowest triplet state of planar aminoboranylidene (3) and the triplet state planar borylnitrene (4) directly by two three-membered ring transition states (TS_1-3 and TS _1-4), respectively. The cis-trans isomerization of iminoborane (1 and 2) by transition state (TS_1-2), the internal conversion of 1 and that of 2 by two transition states (TS_1a-1b and TS_2a-2b) are also considered in the triplet PES. On the other hand, the dissociation product of B-N-H (5) and H atom can be predicted by the dissociation reaction of nonplanar cis-iminoborane (2) and a planar structure aminoboranylidene (3) with the transition state of TS_2-5 and TS_3-5. At the same time, the dissociation product H-B-N (6) and H atom can be predicted by the dissociation reaction of nonplanar cis-iminoborane (2) and a planar structure borylnitrene (4) with the transition state of TS_2-6 and TS _4-6. By analysis of the whole potential energy surface, we can find the isomerization from planar the triplet state aminoboranylidene (3) to the triplet state planar borylnitrene (4) is not carried out in one step directly, but achieved in multistep reactions of TS_1-3 TS_1-4 (3) → (1) → (4).