Super-Supertetrahedral Cluster [Cd16In64S134] : 31- Tetrahedron with a Large Cavity**

Structures constructed from supertetrahedral clusters of TX4 tetrahedra may have giant pores representing more than 80% of their crystal volume and cation-exchange properties.[1] As well as creating porous materials we note that larger clusters are comparable in size with the individual nanocrystallites of tetrahedral sulfide (e.g. CdS) “quantum dots” which show great promise and are currently being investigated as quantum-dot lasers and other optical devices.[2] Similarly, interesting optical properties might be expected in supertetrahedral crystals of semiconducting sulfides.[2h] Clusters labeled Tn have n tetrahedra along each edge.[1] Isolated T2 units are very familiar in chemistry, in molecules such as P4O10, Ge4S6Br4, anions such as [Ge4S10] , and condensed (corner-sharing) in framework crystals particularly of halides,[3] but also of sulfides[4] and of nitrides.[5] A number of extended tetrahedral frameworks based on T3 sulfides, mostly of B[6] or In,[1,7] with a variety of frameworks have been prepared. To prepare the T4 generation of the indium sulfide clusters, we and others have recently shown that in addition to In3+, it is necessary to have divalent metal ions, such as Cd2+.[8,9] The likely distribution of different valence cations in larger Tn clusters was also delineated.[8] A number of compounds with frameworks of alternating T1 and T2 units[10] and recently containing T3 and T5 units[11] have also been described. Other even larger (not supertetrahedral) chalcogenide clusters are known.[12] Herein we report the preparation of the first compound representing the next stage of a structural hierarchy, that is, supertetrahedra of supertetrahedra; specifically a T2 supertetrahedron of T4, a discrete anionic cluster of 214 atoms and 80 tetrahedral centers. This material was synthesized by combining an aqueous mixture (2.2 mL) of In (50.0 mg, 0.44 mmol), S (70.0 mg, 2.18 mmol), Cd(CH3CO2)2·2H2O (200 mg, 0.75 mmol), DBN