The cover picture shows a novel hierarchic endohedral clusterization of H 2 O molecules in the form of a dodecahedron ((H 2 O) 20 , red), a further ™mounted∫ dodecahedron (green), and a rhombicosidodecahedron ((H 2 O) 60 , yellow). The shell/host (Mo atoms blue, O red) is built up by 12 pentagonal {(Mo)Mo 5 } type building blocks (one is highlighted as a blue ring),which are connected by 30 Mo V 2 linkers with the consequence that 20 nanosized Mo 9 O 9 pores/rings of classical crown ether quality are formed in which 20 guanidinium cations are encapsulated (C black, N green). The Mo V 2 type linkers are stabilized by PO 2 H 2 À /SO 4 2À ligands (P/S purple). As the clusterization in the cavity takes place after filling the receptors/pores at the cluster surface with guests, a process is modeled by which a cell converts an extracellular molecular signal into a response. The representative red ring below the blue ring is marked out by the 60 H 2 O ligands coordinated to the pentagonal Mo units, which altogether form a rhombicosidodecahedron (not shown completely). As the geometric forms described are those of Platonic and Archimedean solids Plato and Archimedes feel involved. Further details are reported by A. M¸ller et al. on p. 3756 ff.

Time resolved magnetization measurements have been performed on a spin 1/2 molecular complex, so-called V15. Despite the absence of a barrier, magnetic hysteresis is observed over a time scale of several seconds. A detailed analysis in terms of a dissipative two-level model is given, in which fluctuations and splittings are of the same energy. Spin-phonon coupling leads to long relaxation times and to a particular "butterfly" hysteresis loop.

Pythagorean harmony can be found in the spherical polyoxometalate clusters described here (see illustration for an example of a structure), since there are interesting relationships between the so-called magic numbers (12, 32, 42, 72, 132) relevant for spherical viruses and the number of the building blocks in the cluster. The size of these Keplerate clusters can be tailored by varying the type of connections between the pentagons by means of different spacers.

In their highest oxidation states the early transition metals V, Nb, Ta, Mo, W, and Re form tetrahedral, strongly colored thioanions endowed with some remarkable properties. Thiometalates can be formed by solid-state reactions or in solution from the oxometalates. Polythiometalates with mixed valences can be produced by new types of intramolecular condensation-redox reactions from thioanions. The metal-sulfur bonds can react either nucleophilically or electrophilically, and in the case of the Mo-S bonds this is of biochemical interest. It is important to mention the applications of thiometalates as ligands in complex chemistry (generation of multi-metal complexes, versatile coordination behavior, unique electronic properties of the ligands), in which thiometalato complexes with a variety of electron populations can exist because of the marked electron delocalization. Apart from this, MoSihas a significance in bioinorganic problems, e.g. the nitrogenase problem and Cu-Mo antagonism. 0 Verlag Chemie GmbH. 6940 Weinheim, 057O-0833/81/1111-0934 $02.50/0 Angew. Chem. Int. Ed. Engl. 20, 934-955 (1981) [*' I Microbial Degradation of Chlorinated Arenes, Part 7.-Part 6: [2c]. Angew. Chem. Int. Ed. Engl. 20 (1981) No. I 1 0 Verlag Chemie GrnbH, 6940 Weinheirn. I981 0570-0833/81/II11-0955 $ 02.50/0

Molybdenum monsters: A huge molybdenum cluster, comprising large areas with different local symmetry (in the picture different colors represent different (smaller) Mo fragments) is prepared and characterized. Molybdate fragments, which can tolerate a change of electron density at various positions, can be linked in a tremendous variety of ways according to a split‐and‐link process. Small changes of the boundary conditions, especially the redox conditions, which control growth, as well as the H+ ion concentration, can have a deciding influence on the process.