Etude comparative des méthyl-borazines par RMN

✍ Scribed by G. Beaumelou; M. Pasdeloup; J.-P. Laurent

• Book ID: 102528198
• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: English
• Weight: 426 KB
• Volume: 5
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270051207

✦ Synopsis

A comparative study of borazine (0) and six methyl borazines (1 to 6 ) has been conducted by NMR. It becomes evident that the chemical shift of N-CH, protons hardly varies between mono-, di-and tri-N-methyl borazines, whereas this parameter undergoes a strong change (in all 0.21 ppm, to high field) when one passes from N-trimethyl borazine (HB-NCH,), to hexamethyl borazine (CH,B-NCH,), through a gradual substitution on the three boron atoms (3,4,5 and 6). Moreover, a systematic variation of the parameter 6 has been found between compounds 3, 4 and 5 for the protons which keep precisely the same immediate environment. A qualitative interpretation of this experimental result is proposed in terms of electronic effects general to the hexagonal planar boron/nitrogen ring which characterises these molecules.

RBsumB-Une Ctude comparke du borazine (0) et de six methylborazines (1 ii 6 ) a ktC effectuke par RMN. I1 apparait nettement que le dtplacement chimique des protons N-CH, varie peu entre les mono-, di-et trimkthyl-N borazines alors que ce m&me parametre subit une modification importante (au total 0,21 ppm vers les champs forts) quand on passe du trimkthyl-N borazine (HB-NCH,), B I'hexamtthylborazine (CH,B-NCH,), par substitution progressive sur les trois atomes de bore (cycles 3, 4, 5 et 6). En outre, une variation systCmatique du parametre 6 a pu Ctre dkcelte entre les composts 3,4 et 5 pour les protons qui conservent strictement le m6me environnement immCdiat. Une interprktation qualitative de ce rbsultat expkrimental est proposCe en termes d'effets Blectroniques gtnkralises au cycle hexagonal plan bore-azote qui caractkrise ces molCcules.