The Chemistry of Gallium, Indium, and Mercury Supported by a Sulfur-Rich Coordination Environment

Since the introduction of the tris(2-mercapto-1-R-imidazolyl)hydroborato ligand, [TmR], by Reglinski in 1996, the ligand has gained extensive exposure throughout the periodic table. The ability of the [Tm R] ligand to stabilize such a wide variety of metal complexes may be due to the soft, flexible, and encapsulating manner in which it binds. Indeed, this scorpionate ligand offers a variety of disparate binding modes, some of which were discovered over the course of the research described within this thesis. However, previous work with the [TmR] ligand had curiously neglected the chemistry of the Group 13 metals gallium and indium. We saw an opportunity to expand the chemistry of the [TmR] ligand towards Group 13 metals, since the sterically demanding tris (3,5-di-t-butylpyrazolyl)hydroborato ligand, [TpBut2 ], has been used to stabilize some unique complexes possessing metal-chalcogen multiple bonds. The research described within this thesis extends the application of the [Tm] ligand to the chemistry of low-valent Ga and In and offers a natural comparison to the isoelectronic [Tp] ligand.;While the [TmBut] ligand was used to effectively stabilize monovalent indium and [TmBut]In served as a site of reactivity, when applied to gallium some distinct results were observed in comparison to the related [TpBut2] chemistry. In contrast to the isolation of monomeric, monovalent Ga complexes, several unique cationic and anionic complexes possessing Ga-Ga bonds were isolated. These complexes, which are a consequence of disproportionation of "GaI" pointed to the synthetic accessibility of GaI in situ. In support of this suggestion mixtures of [TmBut] and "GaI" were used to isolate complexes which implicated the accessibility of GaI as a site of reactivity. It is believed that the ability to isolate monomeric, monovalent [TpBut2]Ga is a consequence of the steric protection afforded by the large tert-butyl groups of the pyrazole rings. To probe this suggestion the chemistry of the less sterically hindered [TpMe2] ligand towards low-valent gallium was explored. Significantly, complexes which possess Ga-Ga bonds and are similarly the result of disproportion of "GaI" were isolated. Indeed, the first example of a complex possessing four catenated Ga atoms was isolated and structurally characterized. Analogous to the chemistry of [TmBut], treatment of [TpMe2] and "GaI" with B(C6F 5)3 generated the Lewis base / acid adduct [TpMe 2]Ga→B(C6F5)3. The isolation of a series of related [TmBut] and [TpMe2]Ga complexes possessing Lewis base / acid adduct interactions offered a natural comparison of the relative donor abilities of the two ligand systems.;Since the introduction of the related bis(2-mercapto-1-R-imidazolyl)hydroborato ligand, [BmR], by our research group in 1996, the ligand has found widespread applications. With respect to the main group metals, however, the Group 13 metals had received very little attention. Specifically, [Bm R] complexes of the Group 13 metals were limited to monovalent thallium compounds [BmR]TI and a single indium derivative, namely [Bm Me]InBr2. Therefore, this thesis details research which extends the applications of the [BmR] (R = Me, But) ligand to the chemistry of aluminum, gallium, indium and thallium, including (i) [BmR]2MX compounds that feature a [BmR] ligand to metal ratio of 2:1, (ii) dinuclear [BmR]Ga(I)Ga(I)[BmR] compounds that possess Ga--Ga bonds, and (iii) [BmBut]TlMe 2, a trivalent thallium alkyl compound.;Overall, this thesis describes several recent advances in the chemistry of Group 12 and 13 metals. The chemistry of low-valent Ga and In is extended and contrasted with previous work in this area. Additionally, several new modes of reactivity and bonding are described. A series of related gallium complexes possessing Lewis base / acid adduct interactions offered a natural comparison of the relative donor abilities of two ligand systems. Finally, the suggestion that protolytic cleavage of Hg-alkyls is promoted by higher coordination numbers was supported and mercury was demonstrated to be more selenophilic than thiophilic. (Abstract shortened by UMI.).