Synthesis, characterization and comparison of group 14 pyrrolides and indolides Ph3MX (M = Si, Ge, Sn; X = C4H4N, C8H6N)

The biologically important heterocycles pyrrole, C4H4N, and indole, C8H6N, ought to be useful as reagents in organic synthesis. Unfortunately, working with them has proved to be difficult because they tend to self-polymerize in solution, especially in the presence of acid catalysts. When the self-polymerization can be controlled, however, the pyrrole and indole units should provide an important route to selective N-metal binding, particularly when these ligands are activated by alkyl-lithium reagents. Using this approach, a general synthesis of the group 14 pyrrolides and indolides, Ph3MX (M = Si, Ge, Sn; X = C4H4N, C8H6N), has been developed and the results are reported here. The compounds are formed as high-melting, white crystalline solids and have been characterized by 13C-, 29Si- and 119Sn-NMR, Raman and electron-impact mass spectroscopy as well as elemental analysis. A single-crystal X-ray study of Ph3Si(C4H4N) has shown that the compound is disordered in the tetragonal lattice, even at low temperature (100 K).