Low-Valent Aminopyridinato Chromium Methyl Complexes via Reductive Alkylation and via Oxidative Addition of Iodomethane by a Cr–Cr Quintuple Bond

The reaction of 1 equiv of the deprotonated (sterically demanding) aminopyridine Ap*-H (Ap*-H = (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine) with [CrCl3(thf)3] led selectively to the monomeric complex [Ap*CrCl2(thf)2]. Methylation of [Ap*CrCl2(thf)2] by methyllithium gave rise to a mixture of a dichromium methylidene and a dichromium methyl complex. Alkylation of [Ap′CrCl2(thf)2] (Ap′-H = (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)pyridin-2-yl]amine) afforded selectively the dimethyl complex [Ap′2CrCr(CH3)2]. In addition to reductive alkylation, oxidative addition can be used to synthesize chromium methyl complexes. Selective oxidative addition was observed when CH3I was reacted with the quintuply bonded CrI dimer [Ap′CrCrAp′]. Here, the Grignard-like Cr2 compound [Ap′2CrCr(μ-I)(μ-CH3)] was formed. DFT calculations were performed to investigate the electronic structure of the organometallic complexes.

1当量的去质子化（空间位阻要求高）的氨基吡啶Ap*-H（Ap*-H =（2,6 - 二异丙基苯基）-[6 -（2,4,6 - 三异丙基苯基）吡啶 - 2 - 基]胺）与[CrCl₃(thf)₃]反应，选择性地生成了单体配合物[Ap*CrCl₂(thf)₂]。[Ap*CrCl₂(thf)₂]被甲基锂甲基化后，产生了一种亚甲基二铬和一种甲基二铬配合物的混合物。[Ap′CrCl₂(thf)₂]（Ap′ - H =（2,6 - 二异丙基苯基）-[6 -（2,6 - 二甲基苯基）吡啶 - 2 - 基]胺）的烷基化选择性地生成了二甲基配合物[Ap′₂CrCr(CH₃)₂]。除了还原烷基化，氧化加成也可用于合成铬甲基配合物。当CH₃I与五重键合的CrI二聚体[Ap′CrCrAp′]反应时，观察到了选择性氧化加成。在此，形成了类似格氏试剂的Cr₂化合物[Ap′₂CrCr(μ - I)(μ - CH₃)]。进行了密度泛函理论（DFT）计算以研究有机金属配合物的电子结构。