Goetzfried Sina Katharina, Koenig Sophie Marie Charlotte, Gallati Caroline Marie, Gust Ronald
Department of Pharmaceutical Chemistry, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, Innsbruck A-6020, Austria.
Inorg Chem. 2021 Jun 21;60(12):8546-8553. doi: 10.1021/acs.inorgchem.1c00325. Epub 2021 Jun 7.
The ligand scrambling reaction of gold(I) complexes is a phenomenon occurring primarily in L-Au-X (L = phosphine, -heterocyclic carbene (NHC), and thiol; X = halide and thiol) complexes and has been observed among others for e.g., the bromido[3-ethyl-4-(4-methoxyphenyl)-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2-imidazol-2-ylidene]gold(I) complex (), which underwent ligand rearrangement in aqueous solutions. In this study, we investigated the influence of substituents on the 4-aryl ring of the related (NHC)AuBr complexes (-) in terms of the conversion to the [(NHC)Au] (-) and [(NHC)AuBr] (-) species. Furthermore, the influence of external factors such as solvent, temperature, concentration, and presence of halides (Cl, Br, and I) or hydroxyl ions was studied to gain a deeper understanding of the ligand rearrangement reaction. The substituent on the 4-aryl ring has a marginal impact on the scrambling reaction. Out of the investigated organic solvents (dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol (EtOH), methanol (MeOH), and acetonitrile (ACN)), only ACN separates single complex molecules. In all other solvents, relatively stable ((NHC)AuBr) dimers are present. The addition of water to ACN solutions forces the formation of such dimeric units, starting the transformation to [(NHC)Au] and [(NHC)AuBr]. The rate-determining step is the release of Br from a T-shape intermediate because an excess of KBr terminates this reaction. Furthermore, it is obvious that only single molecules react with halides. The aurophilic interactions between two (NHC)AuBr molecules are too strong in the presence of water and largely impeded reaction with halides. As a single molecule, the reaction with Cl (e.g., in a 0.9% NaCl solution) is notable, while I even leads to a fast and quantitative conversion to (NHC)AuI and finally to [(NHC)Au].
金（I）配合物的配体重排反应是一种主要发生在L-Au-X（L = 膦、杂环卡宾（NHC）和硫醇；X = 卤化物和硫醇）配合物中的现象，例如在溴代[3-乙基-4-（4-甲氧基苯基）-5-（2-甲氧基吡啶-5-基）-1-丙基-1,3-二氢-2-咪唑-2-亚基]金（I）配合物（）中就观察到了这种现象，该配合物在水溶液中发生了配体重排。在本研究中，我们研究了相关（NHC）AuBr配合物（-）的4-芳基环上取代基对转化为[（NHC）Au]（-）和[（NHC）AuBr]（-）物种的影响。此外，还研究了溶剂、温度、浓度以及卤化物（Cl、Br和I）或氢氧根离子等外部因素的影响，以更深入地了解配体重排反应。4-芳基环上的取代基对重排反应的影响很小。在所研究的有机溶剂（二甲基甲酰胺（DMF）、二甲基亚砜（DMSO）、乙醇（EtOH）、甲醇（MeOH）和乙腈（ACN））中，只有ACN能分离出单个配合物分子。在所有其他溶剂中，存在相对稳定的（（NHC）AuBr）二聚体。向ACN溶液中加水会促使形成这种二聚体单元，从而开始向[（NHC）Au]和[（NHC）AuBr]的转化。速率决定步骤是从T形中间体释放Br，因为过量的KBr会终止此反应。此外，很明显只有单个分子会与卤化物反应。在有水存在的情况下，两个（NHC）AuBr分子之间的亲金相互作用太强，极大地阻碍了与卤化物的反应。作为单个分子，与Cl的反应（例如在0.9%的NaCl溶液中）很明显，而I甚至会导致快速定量转化为（NHC）AuI并最终转化为[（NHC）Au]。
