Consortium for Computational Molecular and Materials Sciences (CMS)2 , via Elce di Sotto 8 , I-06123 Perugia , Italy.
Inorg Chem. 2018 May 21;57(10):6161-6175. doi: 10.1021/acs.inorgchem.8b00765. Epub 2018 May 9.
We quantitatively assess the Dewar-Chatt-Duncanson (DCD) components of the Au(III)-CO bond and the charge density polarization at the CO, in a series of neutral, cationic, and dicationic bis- and monocyclometalated gold(III) complexes via charge-displacement (CD) analysis. A striking feature concerns the very small net electron charge flux from CO to the metal fragment which is unexpectedly stable toward both the charge of the complex and the oxidation state of gold (I, III). All systems exhibit a similar trend for the σ charge rearrangement in the region of the carbonyl bond, where, by contrast, the π back-donation trend variation is large, which is strictly correlated to the change in CO bond distance and the shift in CO stretching frequencies, in close analogy with the gold(I) carbonyl complexes. In the whole series of gold(III) compounds, a large Au(III) ← CO σ donation is measured (from 0.19 to 0.31 electrons), as well as a significant Au(III) → CO π back-donation (from -0.09 to -0.22 electrons), which however is not generally able to completely balance the polarization of the CO π electrons in the direction from oxygen to carbon (C ← O) induced by the presence of the metal fragment [LAu(III)]. Surprisingly, all the gold(III) complexes in the series are characterized by a very small anisotropy in the Au(III) → CO in-plane and out-of-plane π back-donation components, in sharp contrast with the marked anisotropy found before for the experimentally characterized [(C^N^C)Au(III)CO] complex. A first attempt to figure out a rationale on the bonding/reactivity relationship for Au(III)-CO is made by performing a comparative study with an isostructural [(N^N^C)Pt(II)CO] complex in a model water-gas shift (WGS) reaction.
我们通过荷移（CD）分析定量评估了一系列中性、阳离子和二价和单价双环金属化金（III）配合物中 Au(III)-CO 键的 Dewar-Chatt-Duncanson（DCD）分量和 CO 上的电荷密度极化。一个显著的特点是，从 CO 到金属片段的净电子电荷通量非常小，这对于配合物的电荷和金（I、III）的氧化态都非常稳定。所有系统在羰基键区域都表现出相似的σ电荷重排趋势，相比之下，π反馈趋势的变化很大，这与 CO 键距离的变化和 CO 伸缩频率的变化密切相关，与金（I）羰基配合物非常相似。在整个金（III）化合物系列中，测量到较大的 Au(III)←CO σ供体（从 0.19 到 0.31 个电子），以及显著的 Au(III)→CO π反馈（从-0.09 到-0.22 个电子），然而，这通常不能完全平衡金属片段 [LAu(III)]存在时诱导的 CO π 电子从氧到碳（C←O）的极化。令人惊讶的是，该系列中的所有金（III）配合物的 Au(III)→CO 面内和面外π反馈分量的各向异性都非常小，与之前对实验表征的 [(C^N^C)Au(III)CO] 配合物发现的明显各向异性形成鲜明对比。通过对具有相同结构的 [(N^N^C)Pt(II)CO] 配合物在模型水煤气变换（WGS）反应中进行比较研究，尝试首次提出 Au(III)-CO 键的键合/反应性关系的基本原理。
