Ferrocene compounds

Initial protonation of iron in protodesilylation of trimethylsilylferrocene was not, however, favoured as a mechanism by Marr and Webster689, who measured rates by the spectroscopic method using hydrochloric acid in 20 vol. % aqueous methanol (Table 235) and found that the rate of desilylation of the ferrocene compound was little more than that for the 4-methoxyphenyl and 2,4-dimethyl compounds. The similarity of the spread of rates in the different media and the similar activation energies and entropies were considered as evidence that the transition states for reaction of all three compounds were similar. The lower activation energy obtained for the 4-methoxyphenyl relative to the ferrocene compound may arise from the different media involved the difference in entropy seems, however, to be rather larger than one might have expected even allowing for the solvent differences. 

Ferrocene compounds containing heteroelements are versatile building blocks for polynuclear complexes. They possess electrochemically active iron centers as well as unique cylindrical shapes. An example of ferrocene-substituted thiolato ligands is l,l -ferrocenedithiolate (S2fc). Its complex with Pd(II) lacks a Pd—Fe bond. 

The bis-benzo-15-crown-5 ferrocene compound [7] containing two vinylic linkages was formed in a mixture of three isomeric components, the cis-cis, cis-trans and trans-trans isomers, which proved inseparable. However, the precedent of insignificant differences found between the magnitudes of the metal cation-induced anodic shifts in the ferrocenyl redox potentials of the respective separated cis and trans isomers [2a] and [2b] led us to use the same isomeric mixture of [7] throughout the subsequent FABMS and electrochemical group 1 and 2 metal cation complexation experiments,... 

Biosensors constructed for ethanol and D-glucose measurements in beverages were built using ferrocene compounds as electron transfer mediators between the coenzyme PQQ of immobilized enzymes glucose (GDH) and alcohol (ADH) dehydrogenases and a carbon electrode surface <2003JOM(668)83>. 

All the derivatives prepared from aldehyde 2 can be obtained as pure enantiomers if desired, e.g., for use as ligands in asymmetric catalysis. Investigations of diastereoselective processes can of course be carried out using racemic phospha-ferrocene compounds. 

This is in contrast to the situation with analogous ferrocene compounds, where the substitution of OH with nucleophiles under the same conditions proceeds... 

Both typical and exceptional examples of the polymerization of a vinyl monomer containing a transition-metal ion are provided by the radical polymerization of vinylferrocene31. Vinylferrocene and its derivatives are polymerized by a radical or a cationic initiator to form a polymer of high molecular weight. The high polymeriz-ability is based on the property that the ferrocene compounds are extraordinarily stable against chemical reactions. 

It is well known that transition-metal salts and metal complexes, unlike non-Werner-type ferrocene compounds, act as inhibitors in the polymerization of vinyl monomers. For example, the radical polymerization of vinylpyridine is strongly inhibited in the presence of Cu(II) or Fe(III)32 However, vinylpyridine with Cu(I)... 

Diarene metals generally decompose under conditions of normal electrophilic substitution, but dibenzene chromium can be metalated with amyl sodium in alkanes, and subsequent reaction with carbon dioxide and dimethyl sulfate results in a complex mixture of mono-, di-, and poly-substituted dibenzene chromium methyl esters. It is interesting that these polysubstituted compounds are homoannular in contrast to the corresponding ferrocene compounds. In view of the scanty evidence and ease of oxidation, it is impossible to conclude whether the diarene metals are less aromatic than the dicyclopentadienyl metals as predicted by simple theory (Sec. III.A). 

Other reactions typical of aromatic systems, such as nitration and bromination, arc not feasible with metallocenes because of their sensitivity to oxidation.,h- However. many of the derivatives that would be produced in these types of reactions can be made indirectly by means of another reaction typical of aromatic systems mctalla-lion. Just as phenyllithium can be obtained from benzene, analogous ferrocene compounds can be prepared ... 

Neuse EW (2005) Macromolecular ferrocene compounds as cancer drug models. J Inorg Organomet Polym Mater 15 3-32... 

The extended Hiickel method, which is a semiempirical quantum chemistry method, is often used as a preliminary step in the DFT study of molecular orbital analysis. The acetylide-bridged organometallic dinuclear complexes 5.2 were studied by Halet et al. using the extended Hiickel method for qualitative analysis and DFT for additional electronic properties [97], The extended Hiickel analysis concluded that the main contribution of the Pt-C bond arises from ct type interactions while the n back-donation is very weak. The DFT/BP86 calculation gives a 2.371 eV HOMO-LUMO gap. The electronic communication parameter Hdb between the bis-ferrocene compound linked with platinum acetylide (5.3) was calculated to be 0.022 eV, compared with 0.025 eV obtained experimentally by Rapenne and coworkers using DFT and the extended Hiickel method [98],... 

Ferrocene compounds and polymers have been used as micelle-forming agents in electrochemical processes for producing organic films usable in electronic materials such as color filters. To increase the concentration of ferrocene in these processes, an ferrocene oligomer having gelling properties has been prepared. 

From the microwave studies of different substituted ferrocene compounds, correlations between properties of the substituents and structural changes were established. It was noted that the carbon-iron bond distance in -qS CsHs-Fe is much more sensitive to substitution on the cyclopentadienyl ligand than the C-C bond distances of the C5H5 ring. This is summarized in Table 2. A linear correlation of the gas phase structural parameter r(Fe-Cp) and the electronegativity of the... 

Table 2 Structural parameters of different ferrocene compounds, (C5H4-Y)-Fe-(C5H4-X), relative oxidation potentials at ambient temperatures, and Hammett substituent constants a ) for cp ligands...

E = S, Se, Te). An abundant number of reviews on ferrocene compounds is available, storehouses in particular are the series of Gmelin volumes [1] and the Annual Surveys published (with some delay) by the Journal of Organometallic Chemistry [2],... 

Three routes have been preferentially used to prepare ferrocene compounds that contain heteroelements directly attached to the metallocene unit borylation, mercuration, and lithiation. 

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