Iron-Mediated Hydrazine Reduction and the Formation of Iron-Arylimide Heterocubanes

The reaction of Fe(N{SiMe3}2)2 (1) with 1 equiv of arylthiol (ArSH) results in material of notional composition Fe(SAr)(N{SiMe3}2) (2), from which crystalline Fe2(μ-SAr)2(N{SiMe3}2)2(THF)2 (Ar = Mes) can be isolated from tetrahydrofuran (THF) solvent. Treatment of 2 with 0.5 equiv of 1,2-diarylhydrazine (Ar′NH−NHAr′, Ar′ = Ph, p-Tol) yields ferric-imide-thiolate cubanes Fe4(μ3-NAr′)4(SAr)4 (3). The site-differentiated, 1-electron reduced iron-imide cubane derivative [Fe(THF)6][Fe4(μ3-N-p-Tol)4(SDMP)3(N{SiMe3}2)]2 ([Fe(THF)6][4]2; DMP = 2,6-dimethylphenyl) can be isolated by adjusting the reaction stoichiometry of 1/ArSH/Ar′NHNHAr′ to 9:6:5. The isolated compounds were characterized by a combination of structural (X-ray diffraction), spectroscopic (NMR, UV−vis, Mössbauer, EPR), and magnetochemical methods. Reactions with a range of hydrazines reveal complex chemical behavior that includes not only N−N bond reduction for 1,2-di- and trisubstituted arylhydrazines, but also catalytic disproportionation for 1,2-diarylhydrazines, N−C bond cleavage for 1,2-diisopropylhydrazine, and no reaction for hindered and tetrasubstituted hydrazines.

双(双(三甲基硅基)氨基)亚铁（Fe(N{SiMe₃}₂)₂，化合物1）与1当量芳基硫醇（ArSH）反应，可得到理论组成为Fe(SAr)(N{SiMe₃}₂)的产物（化合物2）；从四氢呋喃（tetrahydrofuran, THF）溶剂中可分离得到结晶态的双核桥联硫芳基配合物Fe₂(μ-SAr)₂(N{SiMe₃}₂)₂(THF)₂（Ar=均三甲苯基Mes）。将化合物2与0.5当量1,2-二芳基肼（Ar'NH-NHAr'，Ar'=苯基Ph、对甲苯基p-Tol）反应，可得到三价铁酰亚胺-硫醇盐立方烷类配合物Fe₄(μ₃-NAr')₄(SAr)₄（化合物3）。通过将反应投料比（化合物1/芳基硫醇/1,2-二芳基肼）调整为9:6:5，可分离得到位点差异化的单电子还原三价铁酰亚胺立方烷衍生物[Fe(THF)₆][Fe₄(μ₃-N-p-Tol)₄(SDMP)₃(N{SiMe₃}₂)₂]₂（即[Fe(THF)₆][4]₂；其中SDMP=2,6-二甲基苯基硫基）。所分离得到的全部化合物均通过结构表征（X射线衍射）、光谱表征（核磁共振波谱NMR、紫外-可见吸收光谱UV-vis、穆斯堡尔谱Mössbauer、电子顺磁共振波谱EPR）以及磁化学方法完成了综合表征。针对一系列肼类底物的反应研究展现出复杂的化学行为：1,2-二取代与三取代芳基肼可发生N-N键还原反应，1,2-二芳基肼会发生催化歧化反应，1,2-二异丙基肼则发生N-C键断裂反应，而位阻型肼与四取代肼则无反应发生。