Gold Complexes of an Alicyclic Indazole-Derived N-Heterocyclic Carbene: Syntheses, Characterizations, and Ligand Disproportionation

A gold­(I) NHC complex bearing a heteroalicyclic indazolin-3-ylidene ligand, [AuCl­(Indy)] (1) (Indy = 6,7,8,9-tetrahydropyridazino­[1,2-a]­indazolin-3-ylidene), has been synthesized via the silver–carbene transfer method. Conversion of complex 1 to its heavier halido analogues [AuBr­(Indy)] (2) and [AuI­(Indy)] (3) was achieved by metathesis reactions involving LiBr and NaI in acetone, respectively. In contrast to 1 and 2, complex 3 undergoes ligand disproportionation/autoionization upon crystallization, forming the solid complex salts [Au3I2(Indy)4]­[Au3I4(Indy)2] (3′) or [Au­(Indy)2]­[AuI2] (3″) depending on the solvent used. This reversible process assisted by aurophilic interactions, and only occurring in the iodido complex 3, has been studied further by spectroscopic comparison with [Au­(Indy)2]­BF4 (4) and selective conversion of 3 to the gold­(III) species [AuI3(Indy)] (5). All complexes 1–5 have been fully characterized using multinuclei NMR spectroscopies, ESI mass spectrometry, and X-ray diffraction analysis.一种带有杂环脂族吲唑啉-3-亚基配体的一价金(I) N-杂环卡宾（N-heterocyclic carbene, NHC）配合物[AuCl(Indy)]（1，其中Indy为6,7,8,9-四氢吡嗪并[1,2-a]吲唑啉-3-亚基）通过银-卡宾转移法合成得到。将配合物1转化为其重卤代类似物[AuBr(Indy)]（2）与[AuI(Indy)]（3）的过程，可分别通过在丙酮中与溴化锂（LiBr）、碘化钠（NaI）发生复分解反应实现。与1和2不同，配合物3在结晶过程中会发生配体歧化/自电离反应，根据所用溶剂的差异，分别生成固态配合物盐[Au₃I₂(Indy)₄][Au₃I₄(Indy)₂]（3′）或[Au(Indy)₂][AuI₂]（3″）。这种由亲金相互作用介导、仅存在于碘代配合物3中的可逆过程，通过与[Au(Indy)₂]四氟硼酸盐（4）的光谱比对，以及将3选择性转化为三价金(III)物种[AuI₃(Indy)]（5），得到了深入研究。所有配合物1~5均通过多核核磁共振波谱、电喷雾电离（ESI）质谱以及X射线衍射分析完成了全面表征。