First structural evidence for multiple alkali metals between sandwich decks in a metallocene

Abstract

A tetralithio salt (1) derived by treating 1,4-bis(trimethylsilyl)- cyclooctatriene with nBuLi serves as the first structural evidence for a multi-alkali metallocene. Single-crystal XRD confirms two Li + each asymmetrically bind to η 3 and η 4 between two COT′′ rings and two Li + terminally bind to η 3. Solid-state NMR studies confirm the presence of two distinct lithium ion sites while the solution NMR studies suggest the formation of an (COT′′ dianion) ion-pair in solution. Further treating of the tetralithio salt with NaCl leads to linear sodium polymeric chains. Therefore, simply changing the ionic radius changes the molecular structure. © 2012 The Royal Society of Chemistry.