Computational Comparative Mechanistic Study of C−E (E=C,N,O,S) Coupling Reactions through CO₂ Activation Mediated by Uranium(III) Complexes

Abstract

A DFT mechanistic study is undertaken on the functionalization of CO to form C-C, C-N, C-S, and C-O bonds promoted by trivalent uranium complexes (Tp*) UR [Tp*=hydrotris(3,5-dimethylpyrazolyl)-borate ligand, R= -C≡CPh (Cpda-CC), -C≡CSiMe (Cpda-CSi), -NHPh (Cpda-N), -SPh (Cpda-S), and -OPh (Cpda-O)]. These model systems are similar in view of their two-step reaction mechanisms, that is, the insertion of CO into the U-E (E=C, N, O, S) bond to form a [U-κ -O C] intermediate, followed by the reorientation of the carboxylate group to coordinate with the U atom in the κ manner (Cpdb-X, X=CC, CSi, N, S, O). However, the free energy barriers to the rate-determining steps are substantially different, increasing in the order Cpda-S<Cpda-CC<Cpda-Csi<Cpda-N<Cpda-O, which suggests that the bond property of the U-E bonds and the nucleophilicity of the R groups govern the reactivity of the trivalent U complexes. The insertion product may then be silylated in the presence of trimethylsilyl iodide. Two potential mechanisms have been investigated with the -O CR group attacking the Si atom from the side cis (frontside) or trans (backside) to the I atom. The backside pathway was found to be more feasible in view of the free energy barriers and thermicity.

Evaluation of Influencing Factors in Tetravalent Uranium Complex-Mediated CO2 Functionalization by Density Functional Theory

“…In earlier works, , the ligating atoms were found to affect the reactivity significantly in the CO 2 insertion reaction mediated by low valent U complexes. DFT studies proposed that this was rooted from the electronegativity of the ligating atoms.…”

“…During the whole reaction, the spin density of uranium remained essentially constant, suggesting that the oxidation state of uranium did not change. An extensive computational comparative mechanistic study on the C–C, C–N, C–S, and C–O coupling reactions via CO 2 insertion promoted by corresponding trivalent uranium complexes was reported recently, which proposed a similar mechanism for the CO 2 insertion and updated the knowledge on the silylation of the insertion product by suggesting an alternative kinetically more feasible S N 2 pathway.…”

“…Carbon dioxide (CO 2 ) has its dark side as one of the most important contributors to global warming, and its bright side is as an abundant resource of C 1 building block to produce carbon-containing products. − This emphasizes the importance to develop protocols for its conversion to value-added energetic materials. However, its extraordinary thermodynamic stability and kinetic inertness make its activation and functionalization remain a challenge, which is often promoted by d-transition metals. − In recent years, the study has expanded to the application of actinides and lanthanides. − …”

Theoretical Probe for Tris(aryloxide)arene Complexed Low-valent Actinide Ions and Their Structural/Redox Properties

“…然 而, 二价锕系金属配合物虽然可以在溶液中获得并得到 可分离的晶体, 但它们即使在低温下仍不稳定, 这给实 验研究其化学反应性带来了极大的挑战. 在这方面, 理 论计算化学为科学工作者深入探索低价锕系配合物提 供了可靠的工具 [3,4,[19][20][21][22][23][24][25] . 如, 石伟群课题组 [19] 在 Cp'配 位的二价锕系配合物方面的研究工作中, 很好地解释了 已合成配合物的成键和电子性质, 同时对实验未合成的 Pa 和 Am 配合物的结构和性质给予了理论预测.…”

Studi Termodinamika Transpor Ionik Natrium Klorida Dalam Air dan Campuran Tertentu

“…Natrium Klorida mempunyai ikatan ionik yang terbentuk karena kecenderungan atom (26)(27)(28)(29)(30) menangkap/ melepas elektron (31)(32)(33)(34)(35)(36) agar tercapai kongfigurasi gas mulia. Natrium sebagai atom logam (37; 38) cenderung melepaskan elektron (39)(40)(41)(42)(43) dan menjadi ion positif (44)(45)(46)(47)(48) sedangkan atom klorin,cenderung menagkap elektron dan menjadi ion negatif.…”