Organic reactions involving transition metals. Part IV. Carboxylatodiene complexes of rhodium(I) and iridium(I)

The complexes [(diene)MCl]2(M = Rh, diene = norbornadiene, dicyclopentadiene; M = Ir, diene = cyclo-octa-1,5-diene) react with carboxylate ions to give the carboxylate-bridged complexes [(diene)MO2CR]2. Bridgesplitting reactions with triphenylphosphine and ethylenediamine (en) yield the complexes (diene)M(Ph3P)O2CR or [(diene)Rhen]O2CR, characterised by their i.r. and n.m.r. spectra, the latter revealing rapid ligand exchange for the Ph3P-complexes at room temperature. Reaction with hydrochloric acid regenerates the chloro-complexes; oxidative-addition also occurs with the iridium complexes to give the compounds [(cod)IrHCl2]2 and (cod)Ir(PPh3)HCl2.