Carbonyl ligands in modified “picket fence” iron porphyrin complexes: Order and disorder

Abstract

A new modified “picket fence” porphyrin is synthesized and its six-coordinate iron(II) carbonyl derivatives [Fe(MmacTpivPP)(CO)(Py)] and [Fe(MmacTpivPP)(CO)(1-MeIm)] are characterized by single-crystal X-ray, UV-vis and IR spectroscopies. X-ray structural determinations revealed that both [Fe(MmacTpivPP)(CO)(Py)] and [Fe(MmacTpivPP)(CO)(1-MeIm)] are crystallized in the C2/c space group with 2-fold axes passing through the Fe atoms. The FeCO angle of [Fe(MmacTpivPP)(CO)(Py)] is as small as 172.1°, contrasted to 180° of the same angle in [Fe(MmacTpivPP)(CO)(1-MeIm)]. Short intramolecular interactions are found between the terminal oxygen atom of CO and the carbon atoms of the pickets in [Fe(MmacTpivPP)(CO)(Py)]. The characteristic CO stretching frequencies (νCO) of the two complexes are same at 1965 cm−1.