Imidotin cubane clusters

The reaction of the cubane 4 with an excess of SO2 results in the rapid formation of the dimeric compound 38, in which two imidotin cubanes are bridged by two sulfito ligands. The retention of the cubane structure is unexpected, since SO2 is known to insert readily into Sn-NR2 bonds. The dimer 38 is the only known complex in which two [Sn()a3-NR)]4 cubane clusters are strongly linked. 

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... 

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