Southern California Conferences for Undergraduate Research

Southern California Conferences for Undergraduate Research

Synthesis of N-ferrocenyl isonicotinamide and Characterization of Its Adduct with Co(salen)


Bryan BBrautigam, William Farnsworth, Eric McDonald, Eric Patterson, Guang Wu


Steven Contakes, Professor of Chemistry, Westmont College

We are currently investigating the preparation and oxygen reactivity of ferrocene (Fc)-modified CoIIsalen complexes in an attempt to prepare synthetic mimics of the liver detoxification enzyme cytochrome P450. In the present work we prepared and structurally characterized the axial ligand N-ferrocenyl Isonicotinamide and studied its ability to act as an axial ligand in Co(salen) complexes. The synthesis of N-ferrocenyl isonicotinamide was accomplished in 61% yield by coupling isonicotinic acid and aminoferrocene with HOBt/EDC and in 28% by refluxing isonicotinoyl chloride, aminoferrocene, and dry Et3N in CH2Cl2. UV-vis and ESI-MS studies indicate that N-ferrocenyl isonicotinamide reversibly forms a 1:1 adduct with [Co(salen)] under anaerobic conditions in dry CH2Cl2. ESI-MS studies and the dependence of [Co(salen)(pyCONHFc)]’s UV spectrum on concentration indicate that the resulting adduct, [Co(salen)(pyCONHFc)], forms the noncovalent dimer [Co(salen)(pyCONHFc)]2 in CH2Cl2 with a Kd ~ 77 mM. Studies of the concentration-dependence of [Co(salen)(pyCONHFc)]’s oxygen-reactivity indicate that the monomer is oxygen reactive while the dimer is not. Dilute solutions of [Co(salen)(pyCONHFc)] react rapidly with oxygen. In contrast, air-exposed solutions of 0.396 mM [Co(salen)(pyCONHFc)] in CH2Cl2,,which largely consists of the dimer, only react slowly with oxygen over a period of days. UV spectra indicate that the likely product is a k1 superoxide-containing [Co(salen)(O2)(pyCONHFc)] complex. However, bands consistent with both k1 superoxide and a m2-peroxide are present in the IR spectrum. After ~3 days the initial oxygenation product decomposes to give an insoluble brown precipitate we suspect to be [Co(salen)(pyCONHFc)]2(O2) in a zeroth order reaction with an apparent rate constant of 8.8 x 10-6 M/hr. The same or a similar species is formed when solvent is removed from solutions of [Co(salen)(O2)(pyCONHFc)] and the resulting residue is exposed to vacuum.

Presented by:

Eric Patterson


Saturday, November 17, 2012




Broome Library

Presentation Type:

Poster Presentation