Remarkable effect of copper chloride on diiodination of zirconacyclopentadienes

Treatment of zirconacyclopentadienes with two equiv of iodine in THF in the presence of 1.0 equiv of CuCl gave diiododienes in good to high yields without formation of monoiododienes. This is in sharp contrast to the case without CuCl which afforded monoiododienes as major products. For zirconacyclopentenes. CuCl was also effective but the use of ICl was more practical. When zirconacyclopentenes were treated with 2 equiv of ICl, only diiodination products were formed. Preparation of silacyclopentadienes or spiro compounds using the diidodienes was demonstrated. (C) 1997 Elsevier Science Ltd.