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A comparison of diamino- and diamidocarbenes toward dimerization |
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| Authors: | Chin-Hung Lai |
| Institution: | 1. School of Applied Chemistry and Department of Medical Education, Chung Shan Medical University, 402, Taichung, Taiwan |
| Abstract: | In this study, we compare the dimerization of N,N’-diamidocarbene with that of N-heterocyclic carbene (NHC). Less interaction occurred between the filled lone pair of nitrogen and the unfilled lone pair of the carbenic center for a N,N’-diamdiocarbene than did in a saturated NHC because of the resonance between the lone pair of nitrogen and a carbonyl group. Therefore, a N,N’-diamidocarbene exhibits less singlet-triplet splitting. The less singlet-triplet splitting in a heterocyclic carbene containing nitrogen, the more exothermic the dimerization, which is consistent with the conclusion of Thiel et al. (Chem Phys Lett 217:11–16, 1994). In this study, we compare the dimerization of N,N’-diamidocarbene with that of N-heterocyclic carbene. The interaction between the filled lone pair of nitrogen and the unfilled lone pair of the carbenic center becomes lower for a N,N’-diamdiocarbene when comparing with that of a saturated N-heterocyclic carbene because of the resonance between the lone pair of nitrogen and a carbonyl group. Therefore, a N,N’-diamidocarbene has a smaller singlet-triplet splitting. The smaller the singlet-triplet splitting of a heterocyclic carbene containing nitrogen, the more exothermic the dimerization. |
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