Protic NHC Iridium Complexes with β‑H Reactivity–Synthesis, Acetonitrile Insertion, and Oxidative Self-Activation

Protic NHC iridium complexes, obtained from the corresponding azido-phenylene-isocyanide precursor complexes, were investigated for ligand-based reactivity. Under redox-neutral conditions, acetonitrile inserts into the N–H bonds to provide κ2-NHC-imidoyl ligand-based complexes, while under reductive conditions the complex also expels one N–H proton to provide the corresponding deprotonated analogues. Using zinc as a reductor activates the NHC-iridium complex to form an asymmetric bimetallic iridium hydrido complex, in which two anionic N-deprotonated NHCs bridge the bimetallic core. X-ray crystal structures are reported for the azido-phenylene-isocyanide precursor complex, the protic NHC complex, and the asymmetric bimetallic iridium hydride complex. Density functional computations and a QTAIM analysis of the bimetallic iridium hydrido complex are provided.

以相应的叠氮苯异氰基前驱体配合物为原料合成的质子型氮杂环卡宾（Protic NHC）铱配合物，针对其配体基反应性开展了系统研究。在氧化还原中性条件下，乙腈可插入该配合物的N–H键中，生成以κ2-氮杂环卡宾-亚胺酰基（κ2-NHC-imidoyl）为配体的配合物；而在还原条件下，该配合物会脱去一个N–H质子，得到对应的去质子化衍生物。以锌作为还原剂活化该NHC-铱配合物，可得到一种不对称双金属铱氢化物配合物，其中两个阴离子型N-去质子化氮杂环卡宾桥连该双金属核。本文报道了叠氮苯异氰基前驱体配合物、质子型NHC铱配合物以及该不对称双金属铱氢化物配合物的X射线单晶衍射晶体结构。针对该双金属铱氢化物配合物，本文还提供了密度泛函理论（Density Functional Theory, DFT）计算与量子理论原子分子（Quantum Theory of Atoms in Molecules, QTAIM）分析。