Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44781, Bochum, Germany.
Chemistry. 2018 Dec 5;24(68):18043-18051. doi: 10.1002/chem.201803695. Epub 2018 Nov 9.
The reactions of the three triplet ground state arylcarbenes diphenylcarbene 1, fluorenylidene 2, and dibenzocycloheptadienylidene 3 with the Lewis acids H O, ICF , and BF were studied under the conditions of matrix isolation. H O was selected as typical hydrogen bond donor, ICF as halogen bond donor, and BF as strong Lewis acid. H O forms hydrogen-bonded complexes of the singlet carbenes with 1 and 2, but not with 3. This is rationalized by the larger singlet-triplet gap of 3, which does not allow to stabilize the singlet state below the triplet state by hydrogen bonding. With ICF , both 1 and 3 form halogen-bonded complexes of the singlet states of the carbenes. This indicates that halogen bonding stabilizes singlet carbenes more than hydrogen bonding. Carbene 2 reacts differently from 1 and 3 by forming an iodonium ylide, thus avoiding antiaromatic destabilization of the fluorenyl unit. With BF , all three carbenes form zwitterionic Lewis acid/base complexes.
研究了三重基态芳基卡宾二苯卡宾 1、芴基卡宾 2 和二苯并环庚三烯基卡宾 3 与路易斯酸 H2O、ICF3和 BF3在基质隔离条件下的反应。选择 H2O 作为典型的氢键供体，ICF3作为卤键供体，BF3作为强路易斯酸。H2O 与 1 和 2 形成了单重态卡宾的氢键复合物，但与 3 不形成。这可以通过 3 的单重态-三重态能隙较大来合理化，因为氢键不能将三重态以下的单重态稳定下来。与 ICF3，1 和 3 都形成了单重态卡宾的卤键复合物。这表明卤键比氢键更能稳定单重态卡宾。卡宾 2 的反应与 1 和 3 不同，它形成了碘鎓叶立德，从而避免了芴基单元的反芳香性失稳。与 BF3，所有三种卡宾都形成了两性路易斯酸碱配合物。
