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Theoretical investigation on transformation of Cr(II) to Cr(V) complexes bearing tetra-N-heterocyclic carbene and group transfer reactivity |
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| Authors: | Nan Lu Xiaozheng Lan Chengxia Miao Ping Qian |
| Affiliation: | 1. College of Chemistry and Material Science, Shandong Agricultural University, Taian City, P.R. China;2. College of Chemistry and Material Science, Shandong Agricultural University, Taian City, P.R. China Contribution: Funding acquisition, Resources;3. College of Chemistry and Material Science, Shandong Agricultural University, Taian City, P.R. China Contribution: Methodology |
| Abstract: | The mechanism for the transformation among a series of Cr(II) to Cr(V) complexes bearing tetra-N-heterocyclic carbene macrocycle is investigated. The oxidation and aziridination of Cr(II) monomer are studied by local density functional M06L. The former generates Cr(IV) oxo and further oxidizes to cationic Cr(V) oxo. The latter proceeds via two paths with different multiplicity, forming Cr(IV) imide. The Cr(IV) oxo cannot transfer its oxygen atom neither to phosphine nor to alkene because of the high energy barrier and endothermic process. The group transfer reactions are explored for Cr(V) oxo and Cr(IV) imide. The doublet Cr(V) oxo can also exist as quartet Cr(IV)-oxyl radical and promote oxygen transfer to phosphine, resulting in phosphine oxide in one exergonic step. The macrocyclic ligand effect of imido group transfer from Cr(IV) imide is verified by Multiwfn analysis. For 18-ringed imide, the matched orbital type and same-phase overlap reduce the barrier of its 16-ringed analog and facilitate the formation of phosphorus imine. |
| Keywords: | aziridination group transfer reactivity local density functional macrocyclic ligand effect MO analysis |