Facile Formation of Homoleptic Au(III) Trications via Simultaneous Oxidation and Ligand Delivery from [PhI(pyridine)2]2+

We report the first examples of Au­(III) tricationic complexes bound only by neutral monodentate ligands, which are a new class of gold reagents. Oxidative addition to the bis-pyridine Au­(I) cation, [Au­(4-DMAP)2]+, using a series of dicationic I­(III) oxidants of the general form [PhI­(L)2]2+ (L = pyridine, 4-DMAP, 4-cyanopyridine) allows ready access to homoleptic and pseudo-homoleptic Au­(III) complexes [Au­(4-DMAP)2(L)2]3+. The facile oxidative addition of Au­(I) species additionally demonstrates the efficacy of PhI­(L)2]2+ reagents as halide-free oxidants for Au­(I). Comparisons are made via attempts to oxidize NHC-Au­(I)­Cl, where introduction of the chloride anion results in complex mixtures via ligand and chloride exchange, demonstrating the advantage of using the pyridine-based homoleptic compounds. The new Au­(III) trications show intriguing reactivity with water, yielding dinuclear oxo-bridged and rare terminal Au­(III)−OH complexes.本研究报道了首例仅由中性单齿配体配位的三阳离子金(III)配合物，该类配合物属于一类新型金试剂。以通式为[PhI(L)₂]²⁺（L=吡啶、4-二甲基氨基吡啶(4-Dimethylaminopyridine, 4-DMAP)、4-氰基吡啶）的一系列二阳离子型三价碘氧化剂，对双吡啶一价金阳离子[Au(4-DMAP)₂]⁺进行氧化加成反应，可便捷制备均配型及拟均配型三价金配合物[Au(4-DMAP)₂(L)₂]³⁺。该一价金物种的高效氧化加成反应，同时证明了[PhI(L)₂]²⁺类试剂可作为无卤氧化剂应用于一价金的氧化过程。通过对氮杂环卡宾(N-Heterocyclic Carbene, NHC)-一价金-氯化物(NHC-Au(I)-Cl)的氧化尝试可进行对比：体系中引入氯离子后，会因配体与氯离子的交换反应生成复杂混合物，这凸显了采用吡啶基均配型化合物的优势。新型三阳离子金(III)配合物与水展现出有趣的反应活性，可生成双核氧桥联配合物以及罕见的末端Au(III)-羟基配合物。