New Reactivity of High Oxidation State Palladium Complexes.

[摘要] New methodology involving Pd-mediated catalysis that proposes Pd(II/IV) mechanisms has exploded over the past decade. Despite the implication of Pd(IV) intermediates prior to bond-forming C–X reductive elimination in these catalytic reactions, the reported organometallic Pd(IV) complexes in the literature primarily underwent C–C bond-forming reductive elimination. The goal of this dissertation was to design systems to study C–X reductive elimination from observable Pd(IV) complexes. In addition to reductive elimination reactions from Pd(IV), we sought to explore other organometallic reactions at Pd(IV) centers such as C–H activation.The first data chapter presents a detailed mechanistic study of C–O and C–C bond-formation from isolable PdIV complexes. A variety of complexes were synthesized to explore how electronic factors, activation parameters, solvent effects and additive effects are involved in/influence C–O reductive elimination from a PdIV center. Additionally, we identified a system that yielded competing C–O and C–C reductive elimination from PdIV. Therefore, we conducted mechanistic studies to probe C–C bond formation from PdIV; we were able to propose a mechanism for this transformation as well. Chapter 3 investigates sp2 versus sp3-C–X bond formation from PdIV complexes. Interestingly, in all of the systems that were studied, sp3-C–X bond formation out competes sp2 reductive elimination. This chapter presents novel examples of sp3-C–F, C–N and C–O reductive elimination from PdIV in addition to sp3-C–Cl bond-formation. These reactions represent the first examples of high yielding sp3-C–X reductive elimination from PdIV. Lastly, the mechanistic insights gained from these studies lead us to examine systems for sp3-C–X bond-formation that do not use the oxidant to deliver the desired functionality. Next, Chapter 4 of this thesis describes the development a ligand system to explore C–H activation directly at a PdIV center. We designed a complex where reductive elimination is slow and C–H activation is observed. This enabled us to compare the selectively of C–H activation at a PdIV center versus a PdII center. Finally, the thesis concludes with a discussion of the future for the development of PdIV chemistry.

[发布机构] University of Michigan

[效力级别] Palladium

[关键词] High Oxidation State;Palladium;Chemistry;Science;Chemistry