Weakly-coordinating halogenated ligands.

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Parks, Katherine
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Middle Tennessee State University
Potassium, sodium, silver, and thallium(I) halomethanesulfonates and crown adducts of the type MXCH2SO3 and M(18-crown-6)XCH 2SO3 (M = K, Na, Ag, Tl; X= Cl, Br, I) were synthesized. Halomethanesulfonates, postulated to be useful as weakly coordinating anions for homogeneous zirconocene catalysts, are commonly produced from dihalomethanes by nucleophilic substitution reactions, but the reaction is slow and often requires vigorous conditions. The use of the soft metal ions Ag+ and Tl+ was found to facilitate the syntheses. Although the addition of a crown transfer catalyst was also found to decrease the reaction time, the catalyst proved difficult to remove from the final product. In the absence of crown ether, the reactions gave a better yield of products of higher purity. A procedure was found for recycling waste thallium. halides into more useable soluble salts, Tl2SO4 and Tl2SO 3, which were used in the synthesis of thallium. halomethanesulfonates. We were able to prepare crowned cation halomethanesulfonates, [K(18-crown-6)] +(ICH2SO3)-, [Tl(18-crown-6)] +(BrCH2SO3)-, and [Tl(18-crown-6)] + (ClCH2SO3)-, as models for the zirconocene complex, [(C5H5)2(CH 3)Zr][XCH2SO3]. The attempted synthesis of an Ag+ analogue resulted in the production of a suspected triple-crown complex, which probably would not be a good model for the zirconocene. The synthesis of NaICH2SO3 was improved. Proton NMR, IR, TGA, and elemental analyses were used to characterize the products. Nuclear quadrupole resonance (NQR) spectra were used to show the presence of coordination between the metal and halogen atom of the halomethanesulfonates of Ag +, and its absence in those of Tl+.
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