Popov Ivan A, Billow Brennan S, Carpenter Stephanie H, Batista Enrique R, Boncella James M, Tondreau Aaron M, Yang Ping
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA.
Current address: Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, USA.
Chemistry. 2022 May 11;28(27):e202200114. doi: 10.1002/chem.202200114. Epub 2022 Apr 1.
A method to explore head-to-head ϕ back-bonding from uranium f-orbitals into allyl π* orbitals has been pursued. Anionic allyl groups were coordinated to uranium with tethered anilide ligands, then the products were investigated by using NMR spectroscopy, single-crystal XRD, and theoretical methods. The (allyl)silylanilide ligand, N-((dimethyl)prop-2-enylsilyl)-2,6-diisopropylaniline (LH), was used as either the fully protonated, singly deprotonated, or doubly deprotonated form, thereby highlighting the stability and versatility of the silylanilide motif. A free, neutral allyl group was observed in UI (L1) (1), which was synthesized by using the mono-deprotonated ligand [K][N-((dimethyl)prop-2-enyl)silyl)-2,6-diisopropylanilide] (L1). The desired homoleptic sandwich complex U[L2] (2) was prepared from all three ligand precursors, but the most consistent results came from using the dipotassium salt of the doubly deprotonated ligand [K] [N-((dimethyl)propenidesilyl)-2,6-diisopropylanilide] (L2). This allyl-based sandwich complex was studied by using theoretical techniques with supporting experimental spectroscopy to investigate the potential for phi (ϕ) back-bonding. The bonding between U and the allyl fragments is best described as ligand-to-metal electron donation from a two carbon fragment-localized electron density into empty f-orbitals.
人们一直在探索一种从铀的f轨道到烯丙基π*轨道进行直接面对面ϕ反馈键合的方法。阴离子烯丙基基团通过连接的苯胺配体与铀配位，然后使用核磁共振光谱、单晶X射线衍射和理论方法对产物进行研究。（烯丙基）硅烷基苯胺配体N-（（二甲基）丙-2-烯基硅基）-2,6-二异丙基苯胺（LH）以完全质子化、单去质子化或双去质子化形式使用，从而突出了硅烷基苯胺基序的稳定性和多功能性。在通过使用单去质子化配体[K][N-（（二甲基）丙-2-烯基）硅基）-2,6-二异丙基苯胺]（L1）合成的UI（L1）（1）中观察到一个游离的中性烯丙基基团。所需的同配夹心配合物U[L2]（2）由所有三种配体前体制备，但最一致的结果来自使用双去质子化配体[K][N-（（二甲基）丙烯基硅基）-2,6-二异丙基苯胺]（L2）的二钾盐。通过使用理论技术并辅以实验光谱学对这种基于烯丙基的夹心配合物进行了研究，以研究ϕ反馈键合的可能性。U与烯丙基片段之间的键合最好描述为从两个碳片段局部电子密度到空f轨道的配体到金属的电子给予。
