I. Dynamic and thermodynamic investigation of thienyllithium based lithium/tellurium and lithium/iodine ate complexes. II. Dynamic and thermodynamic investigation of phenyllithium based lithium/iodine, lithium/antimony, and lithium/tin ate complexes. III.

The lithium/metalloid exchange reaction is an extremely mild and general procedure for the preparation of organolithium reagents. Ate complexes, first proposed by Wittig, are presumptive intermediates in lithium/metalloid exchange reactions which are widely used to prepare many kinds of synthetically valuable organolithium reagents. We investigated aryllithium ate complexes of Te, I, Sn and Sb via low temperature, heteronuclear NMR spectroscopy. DNMR analysis of the exchange of ArLi with Ar₂Te, Ar₃Sb, and ArI (Ar = diphenylphosphan-2-ylthienyl, phenyl, and m-ethylphenyl) have shown ate complexes to be key exchange intermediates. This provides the first examples of lithium/metalloid exchange systems that proceed exclusively through the ate complex intermediate.; The ability to form and utilize carbon nucleophiles is one the most important applications in organic chemistry. Stabilized organolithium carbanions such as dithioacetal and sulfonyl anions are particularly useful in organic syntheses. A key facet of the our group's research in recent years has been studying solution structure and mechanistic aspects of organolithium reagents in order to develop a better understanding of the relationship between structure and behavior. Solution studies of organolithium reagents have shown that they typically exist as a variety of aggregates, ion pairs, and chelates depending on the solvent mixture. The aggregation state and ion pair status—separated ion pair (SIP) or contact ion pair (CEP)—is known to have large effects on reactivities. Our work on the S_N2 reactions of a series of lithium dithioacetal anions with a variety of alkyl halides in THF at −78°C has shown that the SEP is the only reactive species—the CIP does not react.