Ferrocenecarboxylic anhydride: identification of a new polymorph

Abstract

A new monoclinic polymorph of ferrocenecarboxylic anhydride, [Fe(CH)(CHO)], was obtained. Three molecules are present in the asymmetric unit, two of them being nearly identical (r.m.s. deviation = 0.11 Å), with the Fe atoms on the same side of the anhydride functional group. In the third molecule, the two Fe atoms are located at opposite sides of the functional group (ferrocene-ferrocene pseudo-torsion angle = 146.2°), a very unsual feature in metallocene anhydrides. A network of weak intermolecular hydrogen bonds was also disclosed.

Application of the Curtius rearrangement to the synthesis of 1′-aminoferrocene-1-carboxylic acid derivatives

“…Good yields were obtained, apart for 10 for which the formation of the corresponding anhydride 14 was also noticed. 24,100 Scheme 4. Fca activated esters 10-13 syntheses and formula of anhydride 14.…”