Heterobimetallic (ferrocenyl)indenyl rhodium complexes. Synthesis, crystal structure, and oxidative activation of [eta(5)-(1-ferrocenyl)indenyl]RhL2 [L-2 = COD, NBD, (CO)(2)]

The binuclear [eta(5)-(1-ferrocenyl)indenyl]Rh(NBD) (1), [eta(5)-(1-ferrocenyl)indenyl]Rh(COD) (1a), and [eta(5)-(1-ferrocenyl)indenyl]Rh(CO)2 (2) complexes have been synthesized (NBD = norbornadiene; COD = cyclooeta-1,5-diene). The crystal structure determination showed that the iron and rhodium nuclei are disposed in a transoid configuration in 1 probably to avoid steric repulsions. On the contrary, in 2 the metals are in a cisoid configuration due to the presence of stabilizing pi-hydrogen bonds between the CO's and the hydrogens of the unsubstituted cyclopentadienyl ring. The results of the chemical and electrochemical oxidation of 2 are in favor of the existence of an effective interaction between the two metals.