Hicken Alexandra, White Andrew J P, Crimmin Mark R
SSCP DTP, Grantham Institute, and ‡Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K.
Inorg Chem. 2017 Aug 7;56(15):8669-8682. doi: 10.1021/acs.inorgchem.7b00182. Epub 2017 Mar 22.
A series of copper(I) complexes bearing electron-deficient β-diketiminate ligands have been prepared. The study includes [{{ArNC(CR)}CH}Cu(η-toluene)] (Ar = Mes, R = F, n = 0.5, [1·tol]; Ar = CF, R = Me, n = 1, [2·tol]; Ar = 2,6-ClCH, R = H, n = 0.5, [3·tol]). Reactions of [1-3·tol] with boranes, alanes, a zinc hydride, a magnesium hydride, and a calcium hydride generate the corresponding σ complexes ([1-3·B], [3·B'], [3·Al], [3·Al'], [1-3·Zn], [1·Mg], and [1·Ca]). These species all form reversibly, being in equilibrium with the arene solvates in solution. With the exception of the calcium complex, the complexes have all been characterized by single-crystal X-ray diffraction studies. In solution, the σ-hydride of the aluminum, zinc, magnesium, and calcium derivatives resonates between -0.12 and -1.77 ppm (CD or toluene-d, 193-298 K). For the σ-borane complexes, the hydrides are observed as a single resonance between 2 and 3.5 ppm (CD, 298 K) and bridging and terminal hydrides rapidly exchange on the NMR time scale even at 193 K. Quantification of the solution dynamics by van't Hoff analysis yields expectedly small values of ΔH° and negative values of ΔS° consistent with weak binding and a reversible process that does not involve aggregation of the copper species. The donor-acceptor complexes can be rationalized in terms of the Dewar-Chatt-Duncanson model. Density functional theory calculations show that the donation of σ-M-H (or E-H) electrons into the 4s-based orbital (LUMO or LUMO+1) of the copper fragment is accompanied by weak back-donation from a d-based orbital (HOMO or HOMO-1) into the σ*-M-H (or E-H) orbital.
制备了一系列带有缺电子β-二酮亚胺配体的铜（I）配合物。该研究包括[{{ArNC(CR)}CH}Cu(η-甲苯)]（Ar = 均三甲苯基，R = F，n = 0.5，[1·甲苯]；Ar = CF，R = 甲基，n = 1，[2·甲苯]；Ar = 2,6-二氯苯基，R = H，n = 0.5，[3·甲苯]）。[1 - 3·甲苯]与硼烷、铝烷、氢化锌、氢化镁和氢化钙反应生成相应的σ配合物（[1 - 3·B]、[3·B']、[3·Al]、[3·Al']、[1 - 3·Zn]、[1·Mg]和[1·Ca]）。这些物种均可逆形成，在溶液中与芳烃溶剂化物处于平衡状态。除钙配合物外，所有配合物均通过单晶X射线衍射研究进行了表征。在溶液中，铝、锌、镁和钙衍生物的σ-氢化物在-0.12至-1.77 ppm之间共振（CD或甲苯-d8，193 - 298 K）。对于σ-硼烷配合物，氢化物在2至3.5 ppm之间观察为单一共振（CD，298 K），并且即使在193 K下，桥连氢化物和末端氢化物在NMR时间尺度上也会快速交换。通过范特霍夫分析对溶液动力学进行定量分析，得到预期的小ΔH°值和负ΔS°值，这与弱结合以及不涉及铜物种聚集的可逆过程一致。供体-受体配合物可以根据杜瓦-查特-邓卡森模型进行合理解释。密度泛函理论计算表明，σ-M-H（或E-H）电子向铜片段基于4s的轨道（LUMO或LUMO + 1）的捐赠伴随着从基于d的轨道（HOMO或HOMO - 1）向σ*-M-H（或E-H）轨道的弱反馈捐赠。
