Multispin Systems with a Rigid Ferrocene‐1,1′‐diyl‐Substituted 1,3‐diazetidine‐2,4‐diimine Coupler: A General Approach

This paper describes the stepwise aza‐Wittig reaction of 1,1′‐bis(triphenylphosphoranylidenamino)‐ferrocene with a paramagnetic isocyanate, namely, 3‐isocyanato‐2,2,5,5‐tetramethyl‐2,5‐dihydro‐1H‐pyrrole‐1‐oxyl, and then with substituted arylisocyanates. The intermediate product (a paramagnetic betaine), which is the product of an intramolecular nucleophilic attack of the nitrogen atom of the iminophosphorane moiety on the carbon atom of the carbodiimide functional group, was isolated and structurally characterized. Subsequent interaction of the betaine with arylisocyanates under mild conditions gave spin‐labeled ferrocenophanes with the 1,3‐diazetidine‐2,4‐diimine coupler. It was found that the mutual arrangement of the substituents in the latter depends on the nature of the substituents in the arylisocyanate. Iodophenyl derivatives of 1,3‐diazetidine‐2,4‐diimines were cross‐coupled with the gold(I) nitronyl nitroxide‐2‐ide complex, thus yielding diradicals: metallocenophanes functionalized with various types of nitroxide substituents. Molecular and crystal structures of all mono‐ and diradicals were solved by X‐ray diffraction analysis.