Synthesis distannenes

The synthesis of doubly bonded tin compounds by the coupling of stannylenes, however useful, is limited by the need for a stable stannylene and often a second divalent species (for example, a carbene or isonitrile). The simplest example of this reaction is the formation of tetrakis[bis(tri-methylsilyl)methyl]distannene from two molecules of the corresponding stannylene,83 with which it is in equilibrium in solution as evidenced by NMR spectroscopy.91... 

In contrast to the extensively studied doubly bonded systems of silicon and germanium, the chemistry of the corresponding tin compounds, i.e. distannenes and stannenes, has not been fully disclosed yet probably due to the much higher reactivity and instability of such low-coordinated organotin compounds. In the following sections we briefly describe the synthesis and properties of stable distannenes and stannenes. 

The synthesis of distannenes and diplumbenes are generally achieved by dimerization of stannylenes and plumbylenes (Scheme 11). Although most of them exist as divalent species in solution under equilibrium with the corresponding double-bond compounds, the equilibrium occasionally shifted to the corresponding dimer (double-bond compounds) by crystallization. It is essential to choose the proper size of steric protection groups for the synthesis of doubly bonded systems. 

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