Structural and electronic effects of mono- and bidentate perfluorinated alkoxide ligands in late first-row transition metal complexes

• Main Author: Cantalupo, Stefanie A
• Language: en_US
• Published: Boston University 2015
• Online Access: https://hdl.handle.net/2144/12725

Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at [e-mail]. Thank you. === Seven homoleptic first-row transition metal complexes were prepared with the perfluoro-t-butoxide ligand with three- and four-coordinate geometry. The compounds were prepared via metathesis reactions with the form [M(OC4F9)3]-, M = Mn (1), Fe (2), Co (5), and Zn (7); [M(OC4F9)4]n-, M = Fe (4), Co (6); and the THF adducts [M(THF)(OC4F9)3]- M = Co (5-TBF), and Zn (7-THF). The complexes were synthesized and structurally characterized. Spectroscopic characterization with UV-vis, NMR, and IR will be discussed. Cyclic voltammetry studies of 5 and 6 in conjunction with UV-vis data show the presence of an equilibrium between the three- and four-coordinate complexes with ligand association and dissociation. Using the bidentate perfluorinated pinacolate ligand, ddfp, three complexes were prepared as [M(ddfp)2]2-, in which M =Fe (8), Co (9), and Zn (10). Complexes 8 and 9 have square-planar geometry and are high-spin. The magnetism was studied both in solution and the solid state. The combination of geometry and spin-state is rare for {M04} complexes and 9 is the first example of {C0O4} with this combination, and 8 is the second example of this combination in an {FeO4} system. A five-coordinate Co complex was also structurally characterized (9-OH2). A family of heteroleptic complexes of the form [Fe(X)(OC4F9)3]- in which X = Cl (11), Br (12), or pyridine (13), and [M(py)(ddfp)2]2- for M= Co (14), and Fe (15), were prepared and some were structurally characterized. Analytical data suggests the formation of an iron-amide complex, [Fe(HN(C6H5)(ddfp)2]3-, (16), capable of further reactivity. The synthesis, characterization, and preliminary reactivity studies will be discussed. Two iron aryloxide complexes were synthesized with the pentafluorophenolate ligand, [Fe(OArF)4]2-, (17) and [(OArF)3Fe(μ2-OArF)2Fe(OArF)3]2-, (18). The FeIII complex was formed as a result of presumed ligand oxidation and dissociation, highlighting the vulnerability of aryloxide ligands. A series of isotopically labeled compounds containing a short, strong hydrogen bond were prepared and characterized for neutron diffraction experiments. The compounds, [Cp2Co][D(OAr5)], (19) and d10-[Cp2Co][H(OAr')], (20), were prepared with the partially fluorinated OAr' ligand, bis-(3,5-trifluoromethyl)phenoxide. The synthesis and characterization of these compounds will be discussed.