Stepwise Opening of Cyclic Substituents of Bis(Oxonium) Derivatives of Iron(II) Bis(Dicarbollide) by Pyridine

The interaction of bis(dioxane) and bis(tetrahydropyran) derivatives of iron(II) bis(dicarbollide) [8,8'-{O(CH2CH2)2Х}2-3,3'-Fe(1,2-C2B9H10)2] (Х = O, CH2) with pyridine in an inert atmosphere has been studied. It has been found that the ring-opening of oxonium cycles proceeds stepwise, with the formation of the corresponding mono- and dipyridinium iron(II) complexes. Using the bis(dioxane) dipyridinium derivative as an example, it was found that, when in solution, oxidation of the resulting products to the corresponding paramagnetic complexes of iron(III) is possible. This approach opens the way to obtain bifunctional iron bis(dicarbolide) derivatives with different substituents. The obtained compounds have been characterized by multinuclear NMR and IR spectroscopies, as well as high-resolution mass spectrometry. The structure of the symmetrical dipyridinium iron(II) complex [8,8'-(C5H5NCH2CH2OCH2CH2O)2-3,3'-Fe(1,2-C2B9H10)2] was determined by single crystal X-ray diffraction.