Vasiliu Monica, Edwards Kyle C, Tapu Daniela, Castillo Clarisa E, Stein Trent H, Craciun Raluca, Arduengo Anthony J, Dixon David A
Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336, United States.
Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States.
J Phys Chem A. 2022 May 5;126(17):2658-2669. doi: 10.1021/acs.jpca.2c00921. Epub 2022 Apr 20.
A range of carbene structures and their adducts with one another and with a selection of small-molecule electrophiles and nucleophiles were examined at the composite correlated molecular orbital theory G3MP2 level to explore ground-state "carbenic" structures, their stabilities, and reactivities. Differences between carbene general classification as a singlet electrophilic carbene or singlet nucleophilic carbene and their given reactivity are discussed. A key quantity is the carbon-carbon bond dissociation energy for carbene dimers or the carbene-adduct dissociation energy for other species. The carbene dimer bond dissociation energies span a wide range from 10 to 170 kcal/mol. The hydrogenation energies and singlet-triplet splitting were found to correlate best with the carbene's self-dimerization energy, whereas other descriptors do not. The proton and fluoride affinities of the carbenes alone prove inadequate for classifying reactivity among classes of carbenes. The self-dimerization bond dissociation energy, hydrogenation energy, and singlet-triplet splitting of various carbenes, despite sometimes large differences in proton affinity and other indicators of reactivity, provide usable metrics to correlate substantial amounts of thermodynamic and kinetic (reactivity) information regarding these structures.
在复合相关分子轨道理论G3MP2水平上，研究了一系列卡宾结构及其相互之间的加合物，以及与一些小分子亲电试剂和亲核试剂的加合物，以探索基态“卡宾”结构、它们的稳定性和反应性。讨论了卡宾作为单线态亲电卡宾或单线态亲核卡宾的一般分类与其给定反应性之间的差异。一个关键量是卡宾二聚体的碳-碳键解离能或其他物种的卡宾-加合物解离能。卡宾二聚体的键解离能范围很广，从10到170千卡/摩尔。发现氢化能和单线态-三线态分裂与卡宾的自二聚能相关性最好，而其他描述符则不然。仅卡宾的质子亲和能和氟亲和能不足以对卡宾类别之间的反应性进行分类。各种卡宾的自二聚键解离能、氢化能和单线态-三线态分裂，尽管有时质子亲和能和其他反应性指标存在很大差异，但提供了可用的度量标准，以关联有关这些结构的大量热力学和动力学（反应性）信息。
