Synthesis andRreactivity of Copper(I), Copper(II), Platinum(II) and Platinum(IV) Complexes with Non-dative Heteroatomic Ligands

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Title: Synthesis andRreactivity of Copper(I), Copper(II), Platinum(II) and Platinum(IV) Complexes with Non-dative Heteroatomic Ligands
Author: Munro-Leighton, Colleen
Advisors: Christian Melander, Committee Member
Elon Ison, Committee Member
James D. Martin, Committee Member
T. Brent Gunnoe, Committee Chair
Abstract: Examples of late transition metal complexes with amido, alkoxo and sulfido ligands are relatively rare in part due to enhanced reactivity based on nucleophilicity and basicity of the heteroatomic ligand (X). The highly nucleophilic and basic character of formally anionic X ligands coordinated to metal centers with low oxidation states is attributable to the disruption of ligand-to-metal pi-bonding. Examples of common reactivity for these systems include nucleophilic addition reactions, insertions of unsaturated substrates, acid/base chemistry with acidic C-H bonds and C-H activation reactions with aromatic substrates. In addition to fundamental reactivity studies, these complexes also offer opportunities for incorporation into catalytic processes. Late transition metal complexes with non-dative X ligands have been implicated in several C-X bond forming reactions and have been demonstrated to activate non-polar substrates. Thus, in order to advance the understanding of these reactive systems and to exploit the prospects for synthetic applications toward small molecule transformations, further study is warranted. Presented herein is the study of (IPr)Cu(NR2), (IPr)Cu(OR) and (IPr)Cu(SR) {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene} complexes in the catalytic hydroamination of electron-deficient olefins toward regioselective formation of C-N, C-O and C-S bonds. The substrate scope encompasses alkyl and aryl amines, including primary and secondary variants, as well as alcohols and thiols. Olefins with cyano, acyl, and ester functionalities and vinylarenes are reactive. In a demonstration of potential application, the hydroamination of p-nitrostyrene with N-methylbenzylamine by (IPr)Cu(NHPh) provides a straight-forward single-step route to an anti-arrhythmic agent. Mechanistic studies are consistent with a reaction pathway that involves intermolecular nucleophilic addition of the Cu-amido to free olefin. In an effort to obtain more active catalyst systems that are reactive with unactivated substrates, the preparation of Cu(II), Pt(IV) and Pt(II) amido species has been targeted. The Pt(IV) amido complex (NCN)PtMe2(NHPh) {NCN = 2,6-(pyrazolyl-CH2)2C6H3} has been synthesized and isolated, and reactivity studies have shown the amido moiety to have basic and nucleophilic character. Although (NCN)PtMe2(NHPh) reacts with dihydrogen, C-H activation of benzene does not occur, which is likely due to coordinative saturation of the Pt(IV) complex. To potentially address this issue, two square planar Pt(II) amido species have been synthesized. Initial reactivity studies with (tbbpy)Pt(Me)(NHPh) and (tbbpy)PtCl(NHPh) (tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) indicate that these complexes initiate C-H activation with benzene. These developments could prove beneficial for future efforts toward activation and functionalization of small molecules.
Date: 2008-08-20
Degree: PhD
Discipline: Chemistry

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