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

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 Fc0/+, 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.