Toroidal Main Group Macrocycles: New Opportunities for Cation and Anion Coordination

Inorganic macrocycles, possessing molecular frameworks composed entirely of elements other than carbon, are rare. Even rarer are species analogous to classical organic macrocycles (like crown ethers) that possess the potential ability to coordinate metal ions within their cavities. Recent studies reveal an emerging structural class of valence‐isoelectronic main‐group ligands of general formula [{E(µ‐E′R)}2Y]nx−, which possess fascinating coordination characteristics. Such species can coordinate metal ions within their cavities (using the donor centres Y and E′), their peripheral donor centres (E′) (in an exo fashion) and are also capable of coordinating anions (where Y = N−H). This short review highlights the recent synthetic and structural studies of these unusual ligand systems and pinpoints potential future areas of development. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)