Diverse Reactivity of Bimetallic Nickel Imido Complexes Supported by a Redox-active Ligand
Imido complexes are a class of organometallic compounds composed of a metal bonded with a divalent nitrogen ligand. Monometallic imido complexes have been shown to engage in a variety of chemical transformations such as two-electron group transfer reactions to form N– heteroatom bonds and can insert into C–H bonds to yield C–H amination products. They have also been demonstrated to undergo single-electron processes such as H-atom abstraction to form amido complexes. In contrast to monometallic imido species, the chemistry of bimetallic bridging imido complexes is much less understood. Although bridging dinuclear imido complexes have been isolated, the reported reactivity of these species is limited compared to their monometallic counterparts. While group transfer reactions have been demonstrated for some of these complexes, the majority are considered to be unreactive, and catalytic reactions with bridging dinuclear imido complexes are virtually unknown. In this work we demonstrate that bridging imido complexes can exhibit chemistry that is just as rich as, and in many cases orthogonal to, that of monometallic imidos. The content of this thesis will begin with a discussion of metal–metal bonds in catalytic reactions then focus specifically on reactions of bridging dinickel imido species. Herein we show that dinuclear nickel imido complexes containing a redox-active ligand can undergo catalytic group transfer reactions to aromatic azides, leading to their dimerization via N=N coupling and providing valuable azoarene compounds in high yield. In addition to this reactivity, we also demonstrate that dinuclear imido complexes can lead to novel reaction pathways, and we identify an unprecedented 1,2- addition mechanism for aromatic C(sp2)–H bond activation leading to the formation of C–H amination products. As a whole, these studies indicate that bimetallic imido species offer access to a diverse range of reactivity with promising implications for the development of new catalytic reactions.
Uyeda, Purdue University.
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