Reaction of tetrathiafulvalene derivatives with iron (III).

The ethyl-cyano protected TTF-derivatized ligands 23 and 24 were prepared following reported procedure and characterized. The deprotection of 24 in DMF at room temperature followed by reaction of Fe3+ afforded brown powdered solids. It was found to be insoluble in common organic solvents even in strong coordinating ones such as DMF and DMSO. It does not appear to melt even at 300 degrees Centigrage and the IR spectra showed indications of the presence of the TTF moiety at 1410 and 767 cm-1.. A polymeric chain of Fe-TTF derivative is proposed in the light of the data gathered. On the other hand, deprotection of 23 which was carried out in THF/MeOH at -78 degrees Centigrade and subsequent reaction with Fe3+ afforded orange cubic crystals and black needle-like crystals upon slow evaporation of the acetonitrile solution of the crude product. The orange crystals were confirmed to be the unsymmetrical ligand 23 by TLC and melting-point measurement. The black needle-like crystals were characterized by melting point, IR, UV-Vis and Mass spectroscopy. Comparison with the unsymmetrical ligand revealed that the black crystal is not polymorph of 23, but an Fe-TTF (1:2) complex. Two possible structures, 26 and 28 support the spectral data (IR, UV-Vis and Mass spectra) obtained. However, structure 26, wherein both ligands are completely unprotected, is the more likely composition of the complex based on careful comparison of the IR and MS data. This is the first report of a TTF-derivative ligand complexed with iron