Iron complexes ferrocene

All known pentafluorophenylgold(I) iron complexes are derivatives of ferrocene. In fact, they are obtained mainly by reaction of [Au(CgF5) (tht)] with modified ferrocenes... 

The electroactive units in the dendrimers that we are going to discuss are the metal-based moieties. An important requirement for any kind of application is the chemical redox reversibility of such moieties. The most common metal complexes able to exhibit a chemically reversible redox behavior are ferrocene and its derivatives and the iron, ruthenium and osmium complexes of polypyridine ligands. Therefore it is not surprising that most of the investigated dendrimers contain such metal-based moieties. In the electrochemical window accessible in the usual solvents (around +2/-2V) ferrocene-type complexes undergo only one redox process, whereas iron, ruthenium and osmium polypyridine complexes undergo a metal-based oxidation process and at least three ligand-based reduction processes. 

The process implies a first electrochemical step with a very fast conversion of the ferroceno/ferrocinium couple, due to the short length of the alkyl chain, and a second chemical step with a simple electron transfer between the iron complex in solution and that of the monolayer. Moreover, the thiols block the gold surface in such a way that the Fe(CN)g- oxidation will take place due solely to the ferrocene mediation at the monolayer, and with a very high efficiency (i.e., the catalytic way is observed at potentials 500 mV lower than those corresponding to a gold electrode with a C6SH monolayer). 

There is a certain analogy between the aromatic anions of cyclopentadienide (C5H5 ) and boratabenzene (C5H6B ). l-Methylbora-2,5-cyclohexadienehas a more acidic proton connected to the, sp3-hybridized ring carbon atom than cyclopentadi-ene, due to the same tendency of aromatic anion formation [252, 253]. The related 1-phenyl-1,4-dihydroborabenzene affords the lithium salt of 1-phenylborataben-zene on treatment with tert-butyllithium. Like metallic complexes such as ferrocene formed by cyclopentadiene, boratabenzene also forms such sandwich -complexes with iron and cobalt. The iron complex can be acetylated under Friedel-Crafts conditions. 

Nesmeyanov, Volkenau et al. were the first to replace cyclopentadienyl with another ligand in ferrocene, preparing cyclopentadienyl-arene iron complexes by reaction of ferrocene with aromatic compounds in the presence of AICI3 255-259). 

It is difficult to find direct bonding interaction between the ferrocene iron and the second transition metal in the hetero-bimetallic complexes. Only the mono-triphenylphosphine palladium and platinum compounds fc[E2M(PPh3)] (E = O, M = Pd (Scheme 5-14) [79] E = S, M = Pd [268, 269], and Pt [269]) appear to... 

In view of the current interest in iron complexes for organic synthesis, we have employed dimethyldioxirane for epoxidation purposes. For example, the quite reluctant iron tricarbonyl diene complex with the alkenyl side chain led to the desired epoxide in moderate yield [35]. Also the isoprenyl-substituted ferrocene could be oxyfunctionalized without any difficulties [36],... 

P.L. Pauson (1993) Organo-iron compounds in Chemistry of Iron, ed. J. Silver, Blackie Academic, Glasgow, p. 73 -A good summary of ferrocene chemistry and of other organo-iron complexes. 

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