Electronic Effects in 4-Substituted Bis(imino)pyridines and the Corresponding Reduced Iron Compounds

A family of 4-substituted bis­(imino)­pyridines, 4-X-iPrPDI (4-X-iPrPDI = 2,6-(2,6-iPr2-C6H3NCMe)2-4-X-C5H2N; X = CF3, tBu, Bn, NMe2), has been synthesized and the iron coordination chemistry
studied.
Sodium amalgam reduction of the iron dihalides (4-X-iPrPDI)­FeX2 (X = Cl, Br) in the presence of excess carbon
monoxide furnished the corresponding iron dicarbonyl compounds (4-X-iPrPDI)­Fe­(CO)2. Equilibrium mixtures of the four-
and five-coordinate iron dinitrogen compounds (4-X-iPrPDI)­FeN2 and (4-X-iPrPDI)­Fe­(N2)2 were
prepared by performing the sodium amalgam reduction of the iron dihalides
under a dinitrogen atmosphere. Electrochemical and spectroscopic measurements
were conducted on the free ligands and the iron derivatives to systematically
evaluate the influence of each para pyridine substituent on the electronic
structure of the compound.