Browsing by Subject "antimony"
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Item Organoantimony Lewis Acid as Flouride Receptors and Ligands towards Transition Metals(2013-08-08) Ke, Iou-ShengAs part of our continuing interest in the chemistry of main group Lewis acids, we have now chosen to investigate the Lewis acidic behavior of organoantimony(V) species. In the first part of this thesis, we will describe some of the results obtained in pursuit of this quest including the use of the 9-anthryltriphenylstibonium cation for the fluorescence turn-on sensing of fluoride in water at ppm concentrations. This approach can also be extended to cationic transition metal complexes bearing triarylstibine ligands which readily interact with fluoride anions to afford the corresponding fluorostiboranyl palladium complex. The discovery that anion binding can take place at the antimony atom of coordinated stibine ligands has led us to speculate that the redox state of the metal could be used to control anion binding at antimony. Reaction of (o-(Ph_(2)P)C_(6)H_(4))_(2)SbPh with (Et_(2)S)_(2)PtCl_(2) affords [ClSb(Ph)PtCl(o-dppp)_(2)] (o-dppp = o-(Ph_(2)P)C_(6)H_(4)) which further reacts with PhICl_(2) to afford the tetravalent platinum complex ClSb(Ph)PtCl_(3)(o-dppp)_(2). While the solid state structure of [ClSb(Ph)PtCl(o-dppp)_(2)] and [ClSb(Ph)PtCl_(3)(o-dppp)_(2)] show that the chloride anion is bound to antimony, solution studies indicate that [ClSb(Ph)PtCl(o-dppp)_(2)] is very labile. In addition, we will also present a number of fundamental results which show that electron deficient antimony(III) and antimony(V) centers can behave as sigma-acceptor or Z-ligands toward electron rich transition metal centers. These unusual ligative properties will be illustrated by the structural and computational study of complexes in which chlorostibine moiety is involved in a Au?Sb dative interaction.Item Synthesis and Study of Boron and Antimony Lewis Acids as Small Anion Receptors and Ligands Towards Transition Metals(2012-02-14) Wade, CaseyAlthough fluoride is used at low concentrations in drinking water as a means of promoting dental health, it poses a danger at high exposure levels where it can lead to skeletal fluorosis or other adverse effects. Cyanide is notoriously toxic, and its large scale use in industrial processes warrants the need for close monitoring to remain aware of potential contamination of water sources and other environmental resources. Based on these considerations, it is critical to continue to develop improved methods of monitoring fluoride and cyanide concentrations in water. However, molecular recognition of these anions in water poses considerable challenges. For fluoride, this is due largely to its high hydration enthalpy (?Ho = -504 kJ mol-1), which drastically reduces its reactivity in water. Additionally, the strong basicity of cyanide (pKa of (HCN) = 9.3) may obscure its detection in neutral water due to protonation. In addition to achieving detection of these anions in water, it is most desirable to have information of the detection event relayed in the form of a positive, rather than negative, response (i.e., turn-on vs turn-off). The general strategy of appending cationic groups to triarylboranes imparts beneficial Coulombic, inductive, and sometimes chelate effects that have allowed a number of these Lewis acidic receptors to sense fluoride and cyanide in aqueous environments. With the goal of developing new triarylborane-based receptors that show enhanced affinities for these anions, as well as turn-on responses to detection, a series of pyridinium boranes were synthesized and studied. Having recognized that the inherent Lewis acidity of antimony(V) species might be exploited for anion sensing, we also describe initial studies on the ability of tetraorganostibonium ions (R4Sb+) and cationic transition metal-triarylstibine complexes (R3SbM+) to complex fluoride. Finally, the electropositivity of antimony and its ability to form stable compounds in both the +3 and +5 oxidation states have led us to begin investigations into the bonding and redox reactivity of novel metal stibine/stiborane complexes.