ROLE OF CATION COMPLEXANTS IN THE SYNTHESIS OF ALKALIDES AND ELECTRIDES JAMES L. DYE, MIKHAIL Y. REDKO, RUI H. HUANG and JAMES E. JACKSON Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA I. Introduction 205 A. Historical Perspective 206 B. Alkali Metal Solubilization with Cation Complexants 207 C. Solvent Properties 208 D. Prospects for Crystalline Alkalides and Electrides 209 E. Crystal Structures 210 II. Thermodynamics 211 A. Solution Equilibria 211 B. Thermodynamics of Formation of Crystalline Alkalides and Electrides 212 III. Complexant Properties 214 A. Reducible Groups Ruled Out 214 B. Complexation of Alkali Cations 215 C. Complexant Stability 216 IV. Synthesis Methodology 219 A. Direct Combination 219 B. Metathesis 220 V. Structural Features of Alkalides 221 A. Isolated Anions 221 B. Dimers, Chains and Ion-Pairs 222 VI. Electrides – Anionic or Electronic? 224 A. Electrides as Stoichiometric F-Centers 224 B. Synthesis of Electrides 225 C. Electride Structures and Properties 225 VII. Possible Future Developments 227 References 228 I. Introduction The common understanding of chemists about ‘‘permissible’’ oxida- tion states underwent a profound change with the synthesis by Neil Bartlett in 1962 of the solid noble gas compound Xe[PtF 6 ] (1). To be sure, unusual oxidation states of the elements could be achieved in dilute gases or by matrix isolation. But, to prepare macroscopic sam- ples that could be put into bottles was a major breakthrough. In a 205 ADVANCES IN INORGANIC CHEMISTRY VOLUME 59 ISSN 0898-8838 / DOI: 10.1016/S0898-8838(06)59006-3 r 2007 Elsevier Inc. All rights reserved