Crown block metal compounds

Where the lanthanide ionic radius and the macrocyclic cavity are incompatible, though in hydrous conditions the crown ether is likely to be displaced by water ligands, the crown may still be present in the structure of the crystal as a hydrogen-bonded adduct. This behaviour is seen in [Gd(N03)3(H20)3]-(18-crown-6).445 This type of compound is quite well known in the case of s block metals also, e.g. [Mg(H20)6]Cl2 (12-crown-4)454 and, a more subtle case, [Ca(nitrobenzoate)2(benzo-15-crown-5)]-3H20(benzo-15-crown-5)455 in which an apparent 2 1 complex has only half its crown ligand coordinated to Ca2+. 

There are other examples of Group 1 ions involved in other main-group systems, many of which are organometallic species and outside the scope of this chapter. There are also compounds in which an. s-block ion serves as both a linker in a coordination polymer and as an integral part of a metal aggregate, such as the [K(18-crown-6)]3KSn9 cluster (see Figure 5)." ... 

The affinity of crown thioethers for heavy metals - and their antipathy to the biologically important ions, such as Na, Ca, and Mg -suits crown thioethers particularly well for decorporation of toxic metal ions. Similarly, crown thioethers may find potential use in the hydrometallurgical winning of precious metals such as silver, gold, and platinum, or as the basis for ion-selective electrodes [219]. Other potential applications [220] may arise from use of crown thioethers as structural building blocks or capping members (e.g. (M(9S3) ) for synthesis of metal cluster compounds. 

---