640773-46-2Relevant academic research and scientific papers
Synthesis and reactivity of N-heterocycle-B(C6F 5)3 complexes. 3. generation of N-methylpyrrol-2-yl and N-methylindol-2-yl borate zwitterions with acidic sp3 carbons
Focante, Francesca,Camurati, Isabella,Nanni, Daniele,Leardini, Rino,Resconi, Luigi
, p. 5135 - 5141 (2008/10/09)
The stoichiometric reactions of N-methylpyrrole and N-methylindole with B(C6F5)3 produce the zwitterionic species 2-[tris(pentafluorophenyl)borane]-5H-1-methylpyrrole (8) and 2-[tris-(pentafluorophenyl)borane]-3H-1-methylindole (4), in which a C(α)-B bond and an acidic sp3 methylene carbon are formed in the heterocyclic part of the molecule. Both derivatives present a restricted rotation around the C(α)-B and/or B-C6F5 bonds, and their rotational barriers (13.8 and 14.8 kcal mol-1 for 3 and 4, respectively) were calculated from 1H NMR experimental data. A kinetic study of the reaction, carried out by following the conversion by NMR, gave rate constant values (at 298 K in dichloromethane) of 3 × 10 -5 and 6 × 10-5 M-1 s-1 for 3 and 4, respectively. Complexes 3 and 4 react quantitatively with triethylamine to give the corresponding triethylammonium salts 5 and 6. Both the zwitterionic complexes and their ammonium salts are efficient activators of Ind 2ZrMe2 for the polymerization of ethylene.
