Organoantimony Lewis Acid as Flouride Receptors and Ligands towards Transition Metals

As 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.