Group cationic cluster chemistry

A fascinating recent development in imidotin-cluster chemistry involves the isolation of a series of double cubanes, which contain an Sn7(tt3-NR)8 core. Wright and coworkers have demonstrated that when pyridinyl or pyrimidinyl groups are present on the imido nitrogen centers, the unusual double-cubane clusters 55-60 are obtained (Scheme 2.2.11), rather than the [Sn()a3-NR)]4 cubanes. These clusters are comprised of two interlocked [Sn( a3-NR)]4 cubanes, which share one tin vertex. The central tin center is formally in the +4 oxidation state, so that these double cubanes may be viewed as involving the coordination of two [Sn3()a3-NR)4] anions, such as those present in the clusters 53 and 54, to a central Sn+" cation. The presence of both Sn(II) and Sn(IV) centers was verified by Sn NMR spectroscopy. The deposition of tin metal was observed during the syntheses of 55-60, suggesting that... 

The gold phosphine cationic units tend to attach themselves to the periphery of the osmium cluster anion in the condensation process, and do not form part of the central core as do some other cationic capping groups. The reaction chemistry observed for the mixed osmium-gold clusters is largely centered on the osmium core and does not involve the gold centers directly. 

Fig. 5. Molecular structure of [Fe3(Se2)2(CO)io][SbF6]2S02 (9). [Reprinted with kind permission from Drake, G. W. Schimek, G. L. Kolis, J. W. The coordination chemistry of cationic main group clusters Syntheses and structures of [Fe3(Se2)2(CO)io]2+ and Fe4 (Se2)3(CO)i2]2 t. Inorg. Chim. Acta 1995, 240, 63. Copyright 1995 Elsevier Science S. A., P.O. Box 564, 1001 Lausanne, Switzerland.]...

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