Synthesis, Structure, and Properties of 1,1‘-Diamino- and 1,1‘-Diazidoferrocene

Abstract

We report an improved synthesis of 1,1‘-diaminoferrocene, employing the reduction of 1,1‘-diazidoferrocene with H₂−Pd/C, along with extensive characterization data for both compounds. Diaminoferrocene undergoes a reversible 1e^- oxidation in CH₃CN at a potential of −602 mV vs Fc^0/+, one of the most negative redox potentials for a ferrocene derivative. The chemical reversibility of this process was confirmed by isolation of the stable, 17-electron [Fc(NH₂)₂]⁺ cation as PF₆^-, OTf^-, and TCNE^- salts. In the solid state, diaminoferrocene exists in two conformations: one with the NH₂ groups eclipsed, and the other with the NH₂ groups offset by one-fifth turn around the Cp−Fe−Cp axis. Diazidoferrocene, on the other hand, exhibits only the fully eclipsed conformation in the solid state. The Fe−Cp(centroid) vectors in the diazidoferrocene molecules are roughly aligned with the crystallographic c-axis, and the molecules form layers perpendicular to this axis. The compound is thermally unstable at elevated temperatures, and rapid heating above its melting point results in explosion.