Synthesis Of Chromium, Iron, And Nickel Complexes Using Aryl-Based Chelates As Ancillary Ligands And A Series Of Bis([alpha]-Iminopyridyl) Iron Compounds With Varying Donor Ligands
Several classes of aryl-based chelates containing pyridine, oxazoline, or imine donors and their reactivity with 1st-row transition metals were investigated in light of the potential of carbon-based ligands to impart strong ligand fields. Heterolytic C-H bond activation of 2-phenylpyridine was achieved with Ni(OTf)2. The cyclometalated product and its derivatives undergo substitution, insertion, and additional cyclometalation reactions. Aryl-oxazolines display a range of reactivity patterns which are dependent on the reaction conditions, the metal, and the particular ligand employed. Aryl-aryl coupling, oxazoline ring-opening, and methylene deprotonation were examined, but were tangential to the goal of making metal-aryl bonds. Successful arylation of nickel, iron and chromium was accomplished using a methylated benzyl-oxazoline aryl anion, and the spectroscopic, structural, and magnetic properties of these complexes are described. Tridentate arylpyridylimines or diarylimines undergo facile arylation with cis-(Me3P)4Fe(Me)2 to give low-spin, sixcoordinate iron compounds. Their thermal and oxidation behavior are studied, and the spectroscopic properties of their azaallyl derivatives are compared to previouslyreported, related species. A highly-fluorinated congener of the diarylimine iron complexes was sought, and preliminary evidence of its divergent reactivity is noted. Finally, a series of iminopyridine complexes of the formula (N,N'-[alpha]- iminopyridyl)2Fe(L/X)n have been examined by X-ray and Mössbauer spectroscopy. The redox-active nature of the iminopyridine ligands and the donating ability of the additional L/X ligands have been assessed.
dissertation or thesis