Manicke N, Hoof S, Keck M, Braun-Cula B, Feist M, Limberg C
Institut für Chemie, Humboldt-Universität zu Berlin , Brook-Taylor-Str. 2, 12489 Berlin, Germany.
Inorg Chem. 2017 Jul 17;56(14):8554-8561. doi: 10.1021/acs.inorgchem.7b01347. Epub 2017 Jul 5.
A hexanuclear iron(II) siloxide complex has been prepared by reacting an incompletely condensed silsesquioxane first with NaOMe and then with Fe(OTf). In the process of product formation, the siloxane framework undergoes a transformation and it was shown that this happens already upon addition of base: Treatment of the ligand precursor with NaOMe leads to a completely condensed silsesquioxane cage with 12 Si atoms that is composed of 2 equiv of the tetrasiloxide ligands found in the product complex. Its iron centers form a two-dimensional array reminiscent of the situations found in minerals and two-dimensional oxide films caused by segregation of FeO and silica. As the hexairon(II) assembly contains two high-spin square-planar FeO units-suggested to represent the active sites in Fe-zeolites, which react with NO to generate strongly oxidizing sites-it was treated with MeNO. This led to the oxidation of two of the iron centers to the oxidation state +III and elimination of one iron ion, so that a pentanuclear, mixed valent iron siloxide was formed. All complexes were fully characterized.
通过使不完全缩合的倍半硅氧烷先与甲醇钠反应，然后与三氟甲磺酸铁反应，制备了一种六核铁（II）硅氧化物配合物。在产物形成过程中，硅氧烷骨架发生了转变，并且已表明这种转变在加入碱时就已发生：用甲醇钠处理配体前体导致形成一个由12个硅原子组成的完全缩合的倍半硅氧烷笼，该笼由产物配合物中发现的2当量的四硅氧化物配体组成。其铁中心形成二维阵列，让人联想到在矿物以及由FeO和二氧化硅偏析引起的二维氧化膜中发现 的情况。由于六铁（II）组装体包含两个高自旋平面正方形FeO单元（据认为代表Fe-沸石中的活性位点，其与NO反应生成强氧化位点），因此用甲基亚硝基胍对其进行处理。这导致两个铁中心氧化为+III氧化态并消除一个铁离子，从而形成了一种五核、混合价态的铁硅氧化物。对所有配合物都进行了全面表征。
