Investigations into Pt-C Multiple Bonds With Spectator Scorpionate Ligands Public Deposited

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  • March 20, 2019
  • Lavoie, Katherine
    • Affiliation: College of Arts and Sciences, Department of Chemistry
  • After an overview of Pt organometallic chemistry with an emphasis on Pt(IV) complexes formed through C-H activation, the introduction discusses platinum-carbene complexes. The platinum complexes described here are anchored by scorpionate ligands. Previous investigations into Tp′PtLnXm complexes [Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate] revealed the importance of hemilability as the Tp′ ligand facilitates Pt(II/IV) interconversions. In this thesis the synthesis and metalation of a series of asymmetric scorpionate ligands bearing two pyrazolyl rings and one triazolyl ring are presented. A comparison of octahedral structures of Pt(IV) complexes with P=O and C-H and B-H caps at the pole of the facial tridentate umbrella is included. A series of Pt(IV) carbene complexes of the form [(Tp′)Pt(=C(X)(Y))(Me)2]+ was synthesized. Methylating Pt-carboxamido precursors allowed isolation of [(Tp′)Pt(=C(OMe)NHR)Me2][OTf]. The method for generating these rare Pt(IV) carbenes was extended to synthesize a methoxy stabilized Pt carbene complex, [Tp′Pt(=C(OCH3)CH3)Me2][OTf]. Low temperature protonation of a Pt-vinyl complex, (Tp′)Pt(CH=CH2)(Me)2, generated a small amount of an ethylidene Pt complex. Definitive 13C labeling studies revealed the carbene carbon signal at 500 ppm, a dramatic downfield chemical shift. A Pt(IV)-acetylide was prepared as a potential precursor to a Pt-vinylidene complex. The isolation of a Pt(IV) acetylide complex, (Tp′)PtMe2(C≡CPh) followed by protonation of the acetylide moiety resulted in the observation of a cation Pt-vinylidene complex, [Tp′Pt(=C=C(H)(Ph))(Me)2][B(ArF)4]. The carbon alpha to the platinum center appears at 526 ppm in the C-13 NMR spectrum. Using a heteroscorpionate ligand bound to platinum allowed oxidation of a dimethylPt(II) neutral species with electrophilic reagents, simple acids and acid chlorides, and leads to isomers. The binding properties of the various donor arms dictate the stereochemistry of the products. Investigations into the reactivity of heteroscorpionate tridentate ligands bound to platinum(II) led to C-Cl activation reactions with methylene chloride and 1,2-dichloroethane. Isolation of a dinuclear platinum complex bridged by an ethylene unit produced an unusual proton NMR AA′XX′ pattern in the 1H NMR spectrum due to chirality at each platinum center.
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  • In Copyright
  • Templeton, Joseph
  • Schauer, Cynthia
  • Miller, Alexander
  • Lockett, Matthew
  • Brookhart, Maurice
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2016

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