DUGi

C6-nBnH6(2-n) i C10-nBnH8(4-n): estudi estructural

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@17236

This work is based on a computational study at structural level of the systems C6-nBnH6(2-n) and C10-nBnH8(4-n). The aim of this study is to know better the compounds that contain one or more hexacoordinated carbon atoms through the comparison of the positions boron atoms occupy on the more corresponding structural. We begin from the hypothesis that hypercoordinated carbon compounds are possible because the ionization of some organic systems make these carbon atoms adopt the electronic configuration of boron and make them show geometries that are forbidden for the organic compounds. For this reason, a question was made. In a system with one or more hexacoordinated positions, composed for carbon, boron and hydrogen, are the isomers with boron occupying hypercoordinared positions show more stability that the other ones? Using computational tools, it was optimized every possible isomer for every number of boron atoms “n” that these complexes can show. During the data recollection, the isomers were observed one by one and the energies of those conserving the geometry without showing any negative frequencies were written down. Then, the energies were compared for every sequence of isomers with the same amount of substituted carbon atoms and the behaviour patterns were identified. The results show that for the system C6-nBnH6(2-n) it’s more suitable when the boron atoms occupy the top position of the pentagonal-pyramid and, also, when there is a more than a single boron atom on the base and they are distributed in a non-consecutive form, with at least a carbon atom between them. For the system C10-nBnH8(4-n) have shown more stability too when boron occupies both hexacoordinated positions. In addition, it is observed that the more stable isomers are the ones that show a perfect symmetry, referring to the number of boron atoms per ring, and the maximum number of non-consecutive boron atoms on the two fused cycles. When “n” is odd and a total symmetry is not possible, the stability depends of the patterns told before and that the number of atoms of each type per cycle remains the same or as close as possible. When n=1, and it’s not possible for boron to occupy both hypercoordinated positions simultaneously, the boron atom it’s located in a position shared by the two organic rings, giving more importance at the last pattern explained