Synthesis and characterization of stannoles.

Abstract

Treatment of the diiodotetraphenylstannole with excess lithium cyclopentadiene results in lithium 1,1-dicyclopentadienyl-1-iodo-2,3,4,5-tetraphenylstannole which, along with its bromine analog, are the only lithium salts of five-coordinate {R(, 4)SnX}('-) compounds. This compound contains pseudo-rotating axial- and equitorial-fluxional monohapto-cyclopentadienyl groups. This work was undertaken to synthesize 1,1-disubstituted 2,3,4,5-tetraphenylstannoles. The starting material for this study was 1,1-diiodo-2,3,4,5-tetraphenylstannole. This compound is of value for the organometallic chemist due to its utility as an intermediate in the preparation of many other five-membered heterocyclic tin compounds and to investigate the stereochemistry of hexa- and penta-coordinate complexes of stannoles. The products of these reactions were identified through tin-119m Mossbauer, infrared, proton, and mass spectroscopies. 1,1-Diiodo-2,3,4,5-tetraphenylstannole was prepared in good yield from phenyltin cleavage of hexaphenylstannole by elemental iodine and was found to be thermally stable. Analogous halogenation by elemental chlorine resulted in cleavage of the stannole ring. The great reactivity of iodine attached to tin makes the diiodostannole a highly versitile starting material for the preparation of 1,1-diazido-2,3,4,5-tetraphenylstannole, 1,1-dicyanato-2,3,4,5-tetraphenylstannole, 1,1-diacetato-2,3,4,5-tetraphenylstannole, 1,1-bis(diphenylphosphino)-2,3,4,5-tetraphenylstannole, 1,1-bis(dimethylamino)-2,3,4,5-tetraphenylstannole, 1-fluoro-1-iodo-2,3,4,5-tetraphenylstannole, moreover, the adducts that are formed with pyridine, 2,2'-bipyridine, 1,10-phenanthroline, and 2,2', 2''-terpyridine indicate the ability to form penta- and hexa-coordinate complexes, all having trans-iodine structures.