Iversen Kalon J, Dutton Jason L, Wilson David J D
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, 3086, Australia.
Chem Asian J. 2017 Jul 4;12(13):1499-1508. doi: 10.1002/asia.201700082. Epub 2017 Mar 30.
The endocyclic ring expansion of N-heterocyclic carbene (NHC) rings by transition metal (group 12) and main group (group 13-16) element hydrides has been investigated in a computational study. In addition to previously reported insertion reactivity with Si, B, Be and Zn, similar reactivity is predicted to be feasible for heavier group 13 elements (Al, Ga, In, Tl), with the reaction barriers for Al-Tl calculated to be lower than for boron. Insertion is not expected with group 15-16 element hydrides, as the initial adduct formation is thermodynamically unfavorable. The reaction pathway with group 12 hydrides is calculated to be more favorable with two NHCs rather than a single NHC (analogous to Be), however hydride ring insertion with metal dihydrides is not feasible, but rather a reduced NHC is thermodynamically favored. For group 14, ring-insertion reactivity is predicted to be feasible with the heavier dihydrides. Trends in reactivity of element hydrides may be related to the protic or hydridic character of the element hydrides.
在一项计算研究中，对通过过渡金属（第12族）和主族（第13 - 16族）元素氢化物实现的N - 杂环卡宾（NHC）环的内环扩环反应进行了研究。除了先前报道的与硅、硼、铍和锌的插入反应活性外，预计较重的第13族元素（铝、镓、铟、铊）也具有类似的反应活性，计算得出铝 - 铊的反应势垒低于硼。预计与第15 - 16族元素氢化物不会发生插入反应，因为初始加合物的形成在热力学上是不利的。计算得出，与第12族氢化物反应时，两个NHC比单个NHC（类似于铍）的反应途径更有利，然而，金属二氢化物与氢化物的环插入反应不可行，相反，还原的NHC在热力学上更有利。对于第14族，预计较重的二氢化物具有环插入反应活性。元素氢化物的反应活性趋势可能与元素氢化物的质子性或氢负离子性有关。
