1,3-Diaza[3]ferrocenophanes functionalized with a nitronyl nitroxide group

Abstract

An aza-Wittig reaction of 1,1′-bis(triphenylphosphoranylidenamino)-ferrocene with 4-iodo-, 2,5-difluoro-4-iodo-, pentafluoro-, or 4-methoxycarbonylphenylisocyanates is described here. Intermediate betaines, which are products of a nucleophilic attack of the nitrogen atom of the remaining iminophosphorane moiety on the carbon atom of the carbodiimide functional group, were isolated; their structures were proved by monocrystal X-ray diffraction. Hydrolysis of the betaines under mild conditions gave corresponding arylamino-1,3-diaza[3]ferrocenophanes. On the other hand, as demonstrated, under more rigid conditions, the betaines could be converted into ferrocenophanes with the 1,3-diazetidine-2,4-diimine coupler. The iodo- or diiodo-derivatives of 1,3-diaza[3]ferrocenophanes were cross-coupled with a nitronyl nitroxide-2-ide gold(I) complex to obtain corresponding metallocenophanes functionalized with the nitronyl nitroxide group(s). The molecular and crystal structures of the halogenated and spin-labeled ferrocenophanes were solved by X-ray analysis. In arylamino-1,3-diaza[3]ferrocenophanes, according to cyclic voltammetry, the position of the quasi-reversible oxidation peak associated with the Fe(II)/Fe(III) redox couple deviates within 0.09 V depending on substituents in the arylamino group.