An electrochemical investigation on the reduction path of the arene complexes [CpM(arene)]2+ and [(η-9-SMe2-7,8-C2B9H10)M(arene)]2+ (M=Rh, Ir)

Journal of Solid State Electrochemistry (Impact Factor: 2.45). 11/2007; 11(12):1643-1653. DOI: 10.1007/s10008-007-0324-2


The reduction behavior of the isoelectronic complexes [CpMIII(η6-C6R6)]2+ (M=Rh, Ir; R=H, Me) and [(η-9-SMe2-7,8-C2B9H10)MIII(η6-C6R6)]2+ (M=Rh, Ir; C6R6 = C6H6, C6H5OMe, C6H3Me3) has been studied by cyclic voltammetry and controlled potential coulometry in acetonitrile and propylene carbonate at 253
and 298K, respectively. The extent of chemical reversibility of the pertinent sequences Rh(III)/Rh(II)/Rh(I) and Ir(III)/Ir(I)
is highly dependent on both the nature of the solvent and the intrinsic electronic properties of the arene substituents. The
arene η6 coordination makes the derivatives in their lower oxidation states notably short lived, even if, in some cases, the use of
propylene carbonate improves their stability or causes the increase in their lifetimes before changing the arene coordination
from η6 to η4. Cations [(η-9-SMe2-7,8-C2B9H10)M(η6-C6R6)]2+ were obtained by the bromide abstraction from [(η-9-SMe2-7,8-C2B9H10)MBr2]2 with Ag+ in the presence of benzene and its derivatives. The structure of [(η-9-SMe2-7,8-C2B9H10)Ir(η6-C6H5OMe)](BF4)2 was determined by X-ray diffraction.

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