The objective of this project is to synthesize and characterize an iron tricarbonyl complex that contains a redox active ligand and assess the ability of the complex to catalyze the reduction of CO2 into more useful forms and the reduction of protons to produce hydrogen gas. The development of new catalysts for these reactions is important because they could potentially contribute to a decrease in CO2 levels in the atmosphere. The complex Fe(PhImMePy)(CO)3 (Ph = phenyl, Me = methyl) can be synthesized by reaction of PhImMePy with either Fe(CO)5 in the presence of trimethylamine N-oxide or (bda)Fe(CO)3 (bda = benzylidene acetone). The complex has been characterized by IR, NMR, and single crystal X-ray diffraction. The C-Nimine and C-Npyridyl bond lengths (1.32 and 1.37 Å, respectively) are longer in the complex than in the neutral ligand (1.28 and 1.35 Å, respectively), and the C-C bond length (1.43 Å) is shorter in the complex than in the neutral ligand (1.50 Å). Therefore, the complex can be best described as Fe(I) with the monoanionic ligand. Cyclic voltammetry experiments show that the complex undergoes a reversible reduction at -2.09 V vs. Cp2Fe/Cp2Fe+. Reaction of the complex with the reducing agent potassium graphite, KC8, and phosphine ligands PPh3 and PCy3, have been explored in order to increase the electron density in the complexes. By doing so, we seek to determine the effect on the electronic structure of the complex and to make the complex more susceptible to reaction with protons or carbon dioxide. Based on IR spectral analysis, Fe(PhImMePy)(CO)3 is reduced by KC8, as evidenced by the decrease in carbonyl stretching frequencies from 2000 and 1923 cm-1 to 1937, 1914, and 1861 cm-1 in acetonitrile. In the presence of alkyl and aryl phosphines and trimethylamine N-oxide, a decarbonylating agent, Fe(PhImMePy)(CO)3 undergoes substitution of a carbonyl ligand by phosphine. This species has been detected by 31P NMR spectroscopies with a peak appearing at 55.07 ppm which is evident of coordinated PPh3. Attempts to characterize these complexes structurally by single crystal X-ray diffraction are ongoing. Additionally, the reactivity of the complexes with protons and CO2 is currently being explored.

Synthesis and reactivity of an iron tricarbonyl complex containing redox-active iminopyridine ligand

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