Abstract
Salts, e.g. LiPF$_{6}$, may be dissolved in solid polymers, e.g. (CH$_{2}$-CH$_{2}$-O)$_{n}$. Dissolution is driven by the complexation of the cations by the donor groups on the polymer chains. The resulting solids are coordination compounds with infinite ligands. They form a vital bridge between coordination chemistry in solution and more classical solid-state chemistry. The solid coordination compounds are often referred to as polymer electrolytes. In this paper I present a view of the coordination chemistry of these fascinating compounds which yield elegant structures as well as forming the basis of high technology devices for the 21st century. Topics covered include: the forces driving complexation; the major ligands and complexes; the structures of several model systems; and the physical properties and applications of the materials.