Electronic Interactions in Iron- and Ruthenium-Containing Heterobimetallic Complexes: Structural and Spectroscopic Investigations

The heterobimetallic Ru complexes Cp(CO)Ru(μ-I)(μ-dppm)PtI2 (8), Cp(CO)Ru(μ-I)(μ-dppm)PdI2 (10),
and Cp(CO)RuI(μ-dppm)AuI (12) and their isoelectronic Fe analogues Cp(CO)Fe(μ-I)(μ-dppm)PtI2 (9),
Cp(CO)Fe(μ-I)(μ-dppm)PdI2 (11), and Cp(CO)FeI(μ-dppm)AuI (13) were prepared by the reactions of
Cp(CO)M(κ1-dppm)I (6, M = Ru; 7, M = Fe) with Pt(COD)I2, Pd(COD)I2, and AuI, respectively. All
six complexes were characterized by cyclic voltammetry, IR, UV, and NMR (1H and 31P) spectroscopy,
and elemental analysis. The structures of the I-bridged compounds 8−11 were determined by X-ray
crystallography. Electronic interaction between the two metals is significant for the iodide-bridged
compounds 8−11, as evidenced by the variation in their carbonyl stretching frequencies and UV−vis
spectra, as well as in the shifts of their redox potentials in comparison to the shifts for mononuclear
model compounds. In contrast, compounds 12 and 13, which have only dppm bridges, exhibit limited
interactions between the two metals.