1. ortho-linked polyaryloxide and sterically hindered biphenoxide ligands: Synthesis and metal coordination chemistry. 2. Synthesis, characterization, and reactivity of bis[hydrotris(pyrazol-1-yl)borato]titanium(II)

The first part of this thesis deals with the syntheses and metal coordination chemistry of ortho-linked polyaryloxide ligands. In Chapter 1, a general, effective synthetic strategy involving ortho-lithiation and Suzuki coupling reactions is described for the synthesis of ortho-linked tri- and tetraaryloxide ligands. The coordination chemistry of these ligands is explored for the first time. Using Ti(IV) centers, a complex structural chemistry is observed that originates from bridging interactions between the oxophilic metal centers, and which can be controlled by the introduction of steric bulk at appropriate ortho-ligand positions. The comparative structural coordination chemistry of sterically hindered 3,3'-bis(triphenylsilyl)-1,1 '-bi-2-phenoxide, an isosteric homologue of a chiral binaphthoxide ligand used in asymmetric induction, is presented in Chapter 2. Structural analysis of a series of metal complexes [4-, 5-, 6-coordinate on Fe(II, III), Cr(II), Ti(IV)] synthesized using this ligand reveals that the steric influence of the hindered chelate over the metal environment, while significant, is also compliant and moderated by deformational and conformational changes within the ligand itself.;The second part of this thesis concerns the chemistry of bis[hydrotris(pyrazol-1-yl)borato]titanium(II) (Tp2Ti). The synthesis and characterization of Tp2Ti is described in Chapter 3. Tp2Ti is a rare example of a stable Ti(II) complex ligated solely by hard donors. This study completes the Tp 2M series for 3d transition metals; existing gaps in the characterization of other members in this series are filled. Metal-nitrogen distances and M(II)/M(III) redox potentials follow periodic trends as modified by orbital splittings. Reactivity of Tp2Ti is discussed in Chapter 4. Tp2Ti, unlike other Tp2M complexes of transition metals, displays redox-mediated inner sphere reactivity with chalcogens (S, Se), diazoalkanes, organoazides (or isocyanates or 0.5 equivalent azoarenes) to form Ti(IV) complexes with group transfer or substrate addition. Reactions with a strong proton donor, [H(OEt2)2]BAr', aryl diazonium halides, and oxygen lead to Ti(III) complexes. An underlying theme in the inner sphere reactivity is the formation of a (kappa3-Tp)(kappa 2-Tp) bis-chelate structure.