| The primary focus of this dissertation is the development of the chemistry of organo-Zintl clusters. The goal of the project was to put into place the necessary building blocks so as to bring germanium deltahedral clusters inline with mainstream organic chemistry.;After introducing the foundations of Zintl chemistry (Chapter 1), the first method for synthesizing organo-Zintl clusters is discussed, namely the 'halide' route (Chapter 2). This technique allows organo-Zintl clusters to be synthesized by reacting naked Ge94- clusters with R-X substrates to form [Ge9-R]3-, [R-Ge9-R]2-, and [R-Ge9-Ge9-R] 4-. Investigations show this route to be general, and applicable to primary, secondary, and tertiary carbon centers. Moreover, it is independent of steric bulk, as evidenced by the characterization of [Ge9-C 10H15]3- from reactions with the bulky, tertiary bromoadamantane.;The second method for synthesizing organo-Zintl clusters, the 'alkyne' route, is discussed in Chapter 3. Reactions between Ge9 4- and both terminal and internal alkynes (R-C≡C-H and R-C≡C-R') result in the addition to the clusters and hydrogenation of the parent alkyne to form alkenylated clusters, [Ge9-CR'=CH-R]3- and [Ge9-(CR'=CH-R)2]2- (where R' = H or any R group). The organo-Zintl and organometallic-organo-Zintl species, [Ge9-CH=CH-Ph-OMe]3- and [Ge9-(CH=CH-Fc) 2]2- (Fc = ferrocenyl) respectively, where structurally characterized by X-ray diffraction, along with reactions with a variety of internal and terminal alkynes by mass spectrometry.;Zintl clusters in general are only soluble in a limited number of non-traditional solvents such as ethylenediamine and liquid ammonia, and occasionally dimethylformamide. The results presented in Chapter 4 demonstrate that the alkali metal cation (normally K+) of organo-Zintl clusters can be exchanged for quaternary ammonium cations, R4N+.;Chapter 5 presents the results of a systematic investigation of the reactions of nine-atom deltahedral clusters of germanium (Zintl ions, Ge9 n-) with alkynes and alkyl halides. The reaction pathways were probed in depth using various, appropriately substituted alkynes and organic halides, including some typical mechanistic probes and radical clocks. The regioselectivity and stereoselectivity of the reaction with alkynes was examined by systematically varying the steric and electronic nature of the substituents. The studies showed that the Zintl clusters act as strong, anionic nucleophiles towards the alkynes and primary and secondary alkyl halides but, most likely, as electron donors in reactions with tertiary alkyl halides and halogenated olefins.;Chapter 6 further develops the nucleophilic reactivity of Zintl clusters. Specifically, their reactivity towards substrates with two different electrophilic centers is probed, namely: (a) organostannyl center + alkyne, (b) halide carbon center + alkyne, and (c) halide carbon center plus carbonyl group. These reactions show the preference of the clusters for organostannyl centers over alkynes, and halide carbon center over either of the other two.;Chapter 7 discusses the stability towards H2O that organo-Zintl clusters exhibit. This compatibility with H2O is coupled with their non-reactivity towards aldehydes to demonstrate that subsequent organic transformations are possible with organo-Zintl clusters.;Chapter 8 involves a break from germanium-based clusters, and discusses the results of some investigations into the reactivity of bismuth-based Zintl anions towards Ni(CO)2(PPh3)2. (Abstract shortened by UMI.)... |
