Pentamethylcyclopentadienyl-rhodium and -iridium halides. Part III. Reactions with cyclohexadienes

Abstract

The dimeric dichloropentamethylcyclopentadienyl-rhodium and -iridium complexes (I) react with both cyclohexa-1,3- and 1,4-diene to give the π-cyclohexa- 1,3-diene-(pentamethylcyclopentadienyl)-rhodium and -iridium complexes. (IV). During this reaction, isomerisation of the uncomplexed cyclohexa-1,4- to the -1,3-diene occurred. The rhodium complex (IV) was a catalyst for the disproportionation of cyclohexa-1,3-diene to cyclohexene and benzene. This reaction was strongly assisted by the presence of the ethanol and base. Mechanisms for the complex formation, isomerisation, and disproportionation are suggested.