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Ligand Exchange, Hydrides, and Metal-Metal Bonds: An Investigation into the Synthesis, Structure, and Reactivity of Group 12 Metal Complexes in Sulfur and Nitrogen-Rich Environments

Kreider-Mueller, Ava Rose

The molecular structures of [κ³-S₂H-Tmᴮᵘᵗ]Na(THF)₃ and [κ³-S₂H-Tmᴬᵈ]Na(THF)₃ have been obtained, which is significant as these are the first two examples of monomeric κ³-S₂H coordinate sodium compounds to be reported. Based on an extensive structural analysis of all of the [Tmᴿ]M compounds listed in the Cambridge Structural Database, a set of criteria has been generated that can be used to classify [Tmᴿ] ligands according to their coordination modes. Compounds exhibiting κ³-S₃ coordination are found to be the most prevalent, as are compounds exhibiting 0:3 conformation modes.
A series of [Tmᴮᵘᵗ]CdO₂CR complexes (R = C₆H₄-4-Me; C₆H₄-4-F; C₆H₃-3,5-F₂; C₆H₃-2,6-F₂; C₃H₆Ph; 9-An; and tridecyl) has been prepared via the reaction of [Tmᴮᵘᵗ]CdMe with the corresponding carboxylic acids. [Tmᴮᵘᵗ]ZnO₂CR (R = C₆H₄-4-Me; C₆H₄-4-F; C₆H₃-3,5-F₂; C₆H₃-2,6-F₂; 9-An) have been prepared by an analogous method. In addition, two thiobenzoate complexes, [Tmᴮᵘᵗ]MSC(O)Ph (M = Zn, Cd), have been obtained via the treatment of [Tmᴮᵘᵗ]MR (R = Me) with thiobenzoic acid. An extensive structural analysis of the [Tmᴮᵘᵗ]MO₂CR and [Tmᴮᵘᵗ]MSC(O)Ph complexes has been provided, based on single crystal X-ray diffraction and NMR spectroscopy. In addition, degenerate benzoate exchange between [Tmᴮᵘᵗ]MO₂C(4-C₆H₄-F) and 4-fluorobenzoic acid has been investigated by ¹⁹F-NMR lineshape analysis over a large temperature range (195-262 K). The acid concentration dependence of the rate for the exchange process supports an associative exchange mechanism. [Tmᴮᵘᵗ]MO₂C(4-C₆H₄-F) benzoate exchange is extremely rapid on the 19F NMR timescale at 25˚, and has been observed to be faster for [Tmᴮᵘᵗ]CdO₂C(4-C₆H₄-F) than for [Tmᴮᵘᵗ]ZnO₂C(4-C₆H₄-F).
The reactivity of [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) towards different thiols, ArSH (Ar = C₆H₄-4-F, C₆H₄-4-Buᵗ, C₆H₄-4-OMe, C₆H₄-3-OMe), has been investigated using various NMR techniques. In contrast to the results of our degenerate benzoate exchange studies, thiolate exchange between [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) and ArSH is slow on the ¹H NMR timescale. Even at elevated temperatures, the NMR signals for the reaction species remain resolved with minimal linebroadening. The equilibrium constants for the reactions of [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) with ArSH (Ar = C₆H₄-4-But, C₆H₆-4-OMe, C₆H₄-3-OMe) have been calculated and determined to be indistinguishable, with equilibrium favoring the [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) and ArSH species. Additionally, the reactivity of [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) toward phenols, ArOH (Ar = Ph, 2,6-diphenylphenol), has been investigated. While [Tmᴮᵘᵗ]CdS(C₆H₄-4-F) has been found to be unreactive toward ArOH, [Tmᴮᵘᵗ]CdSOAr (Ar = 2,6-diphenylphenol) reacts immediately (C₆H₄-4-F)SH, resulting in complete conversion to [Tmᴮᵘᵗ]CdS(C₆H₄-4-F). Two monomeric [Tmᴮᵘᵗ]CdE(2-C₅H₄N) complexes (E = S, Se) have also been prepared, and structurally characterized.
A monomeric, terminal zinc hydride complex, [Tmᴮᵘᵗ]ZnH, has been prepared via the reaction of [Tmᴮᵘᵗ]ZnOPh with phenylsilane. The molecular structure of [Tmᴮᵘᵗ]ZnH has been obtained by single crystal X-ray diffraction techniques, and the reactivity of [Tmᴮᵘᵗ]ZnH towards various reagents has been investigated. [Tmᴮᵘᵗ]ZnH reacts rapidly with ArEH (EAr = OPh, S(C₆H₄-4-F), SePh) to form [Tmᴮᵘᵗ]ZnEA via H₂ elimination. [Tmᴮᵘᵗ]ZnH reacts with CO₂ to form [Tmᴮᵘᵗ]ZnO₂CH via CO₂ insertion into the Zn-H bond. [Tmv]ZnO₂CH can also be prepared by the reaction of [Tmᴮᵘᵗ]ZnH with formic acid. [Tmᴮᵘᵗ]ZnH reacts rapidly with ZnEt₂ to form [Tmᴮᵘᵗ]ZnEt. The reaction of [Tmᴮᵘᵗ]ZnH with CpMo(CO)₃H resulted in the formation of a metal-metal bonded complex, namely [Tmᴮᵘᵗ]Zn-MoCp(CO)₃.
A series of [Tmᴮᵘᵗ]M-M'Cp(CO)₃ heterobimetallic complexes (M = Zn, Cd; M' = Cr, Mo, W) has been prepared via the reaction of [Tmᴮᵘᵗ]MR (R = Me) with CpM'(CO)₃H. An extensive structural analysis of these complexes is provided, based on X-ray diffraction and NMR spectroscopy. Each of these complexes features a direct M-M' bond, which is supported by two partially bridging carbonyl ligands. Only a few complexes featuring an M-M' bond have been structurally characterized, and the molecular structures of [Tmᴮᵘᵗ]Zn-CrCp(CO)₃ and [Tmᴮᵘᵗ]Cd-WCp(CO)₃ represent the first two structures reported for compounds featuring either a Zn-Cr or Cd-W bond.
The coordination chemistry of [tpyᴬʳ] (Ar = p-tolyl, mesityl) and [bppᴮᵘᵗ] with various main group and transition metals has been investigated. [tpyᴬʳ]MX₂ complexes (M = Co, Zn; X = Cl, I) are prepared by the reaction of [tpyᴬʳ] with the dihalide MX2 complex. [bppᴮᵘᵗ]MX2 (M = Fe, Co, Zn, Cd; X = Cl, I) complexes are prepared by an analogous method. Each of these [tpyᴬʳ]MX₂ and [bppᴮᵘᵗ]MX₂ complexes have been characterized by single crystal X-ray diffraction. The [bppᴮᵘᵗ]LiI compound was unexpectedly obtained from the reaction of [bppᴮᵘᵗ]FeCl₂ with MeLi, which is significant as it is the first example of an alkali metal complex featuring a [bppᴮᵘᵗ] ligand that has been structurally characterized.


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More About This Work

Academic Units
Thesis Advisors
Parkin, Gerard
Ph.D., Columbia University
Published Here
August 6, 2014
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