Why do Organolithium Monomers have Strange Structures?

Abstract

“Replacement of hydrogen atoms by lithium atoms may radically alter the stereochemistry of the parent hydrocarbon”. Thus can be summarized some of the most important findings of the imaginative computational work of Schleyer and his coworkers.¹ What fundamental property of lithium is primarily responsible for the unexpected geometrical preferences of perlithio hydrocarbons? Is there some way to predict the geometry of these molecules? These and related questions can be dealt with within the framework of MOVB theory in a way which illustrates the basic utility of the Induced Deexcitation (ID) model presented in the previous chapter as well as the way in which MOVB theory^2,3 can be used in order to produce novel insights regarding the mechanism of vacant orbital participation in chemical bonding. The former illustrative application of the theory is made possible by the fact that Li is a weak overlap binding (overbinding) ligand which can readily induce core deexcitation while the latter is made possible by the fact that Li has low lying vacant 2p orbitals which can combine with doubly occupied orbitals to define new bonds or they can function as hybridization “holes” to promote more efficient “covalent” carbon-lithium bonding. At the outset, we state that this work has been totally motivated by the calculational work of Schleyer and his collaborators⁴ which was published at the time when we were in sore need of well established facts to test the central ideas of MOVB theory, such as the ones described in this and other chapters.