PI-OLEFIN-IRIDIUM COMPLEXES .21. SYNTHESI S AND CRYSTAL-STRUCTURE OF HETEROBINUCLEAR COMPLEXES WITH BOAT-SHAPED, SYNFACIALLY BOUND ETA(3)-ETA(3) BENZENE BRIDGE

CpIr(eta4-C6H6) (2) has been obtained in high yield by a four-step syn thesis. Thermal reaction of 2 with CpCo(C2H4)2 and photochemical react ion of 2 with CpRh(C2H4)2 or CpRh(C2H4)2 give the compounds mu-(eta3: eta3-C6H6)CoIrCp2 (3), mu-(eta3:eta3-C6H6)RhIrCp2 (4), and mu-(eta3:et a3-C6H6)(RhCp)(IrCp) (5), respectively. The X-ray crystallography dat a of 3 and 4 reveal a boat-shaped conformation of the synfacially brid ging benzene ligand with a rather long Co-Ir bond distance in 3 and a relatively short Rh-Ir bond length in 4 which are caused by almost con stant folding angles of the benzene unit. The dynamic behaviour of the benzene bridge was investigated by NMR spectrometry.