N,N-addition of frustrated Lewis pairs to nitric oxide: an easy entry to a unique family of aminoxyl radicals |
| |
Authors: | Sajid Muhammad Stute Annika Cardenas Allan Jay P Culotta Brooks J Hepperle Johannes A M Warren Timothy H Schirmer Birgitta Grimme Stefan Studer Armido Daniliuc Constantin G Fröhlich Roland Petersen Jeffrey L Kehr Gerald Erker Gerhard |
| |
Institution: | Organisch-Chemisches Institut, Westf?lische Wilhelms-Universit?t, Corrensstrasse 40, 48149 Münster, Germany. |
| |
Abstract: | The intramolecular cyclohexylene-bridged P/B frustrated Lewis pair Mes(2)P-C(6)H(10)-B(C(6)F(5))(2)] 1b reacts rapidly with NO to give the persistent FLP-NO aminoxyl radical 2b formed by P/B addition to the nitrogen atom of NO. This species was fully characterized by X-ray diffraction, EPR and UV/vis spectroscopies, C,H,N elemental analysis, and DFT calculations. The reactive oxygen-centered radical 2b undergoes a H-atom abstraction (HAA) reaction with 1,4-cyclohexadiene to give the diamagnetic FLP-NOH product 3b. FLP-NO 2b reacts with toluene at 70 °C in an HAA/radical capture sequence to give a 1:1 mixture of FLP-NOH 3b and FLP-NO-CH(2)Ph 4b, both characterized by X-ray diffraction. Structurally related FLPs Mes(2)P-CHR(1)-CHR(2)-B(C(6)F(5))(2)] 1c, 1d, and 1e react analogously with NO to give the respective persistent FLP-NO radicals 2c, 2d, and 2e, respectively, which show similar HAA and O-functionalization reactions. The FLP-NO-CHMePh 6b derived from 1-bromoethylbenzene undergoes NO-C bond cleavage at 120 °C with an activation energy of E(a) = 35(2) kcal/mol. Species 6b induces the controlled nitroxide-mediated radical polymerization (NMP) of styrene at 130 °C to give polystyrene with a polydispersity index of 1.3. The FLP-NO systems represent a new family of aminoxyl radicals that are easily available by N,N-cycloaddition of C(2)-bridged intramolecular P/B frustrated Lewis pairs to nitric oxide. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|