Redox metallocene

A60. J. P. Candlin, K. A. Taylor, and D. T. Thompson, "Reactions of Transition-Metal Complexes. Elsevier, Amsterdam, 1968. A review of types of reactions of metal complexes (e.g., substitution, combination, redox) reactions with various reagents (e.g., hydrocarbons, halides, carbon monoxide, and isonitrile) and preparation of new stabilised organic systems (e.g., metallocenes, carbenes). Intended for research workers, consequently written at a fairly high level, with emphasis on organometallics. A61. H. J. Keller, NMR-Untersuchungen an Komplexverbindungen. Springer, Berlin, 1970. Expansion of review article 37.1. 

Figure 2. Band edge positions obtained over a period of three weeks for p-and n-type WSe2 -CH3CN interfaces containing metallocene redox couples (ferrocene, FER decamethylferrocene, DFER and acetylferrocene, AFER) each at three concentrations (preceding letter refers to high.H medium,M and low, L). Two different electrodes were used to obtain the data for n-WSe2 with doping densities between 1016 -1017 cm-3.

Obtained in MeCN solution containing 0.1 mol dm 3 Bu°NBF4 as supporting electrolyte. Solutions were 1 x 10 3 mol dm 3 in compound and potentials were determined with reference to an Ag/Ag+ electrode at 21 1°C, 50 mV s scan rate. > p, and represent the anodic and cathodic peak potentials. Cathodic shifts in the metallocene redox couples produced by the presence of anion (5 equiv) added as their tetrabutylammonium salts. As the concentration of the anion increased, the cathodic current peak potential of the ferrocene/ferTOcenium redox couple began to exhibit the features of an EC mechanism. 

As happens for ferrocenes, almost all metallocenes can be incorporated in multimetallocenic assemblies. We thus conclude the discussion by considering the redox behaviour of bis(fulvalene)dinickel(II,II), [Ni2(>/5 75-CioH8)2]. Its X-ray structure is shown in Figure 50.97 The inequivalence of the Ni-C and C-C distances is attributed to the structural constraints imposed by the two bridges which join the two nickelocene units. 

An exhaustive treatment of the electrochemical behaviour of transition metal complexes is beyond the scope of this book, because the enormous number of ligands available, combined with the possibility to prepare mono- and/or polynuclear complexes using identical or mixed ligands, would render such a task almost impossible. Therefore, the discussion is limited to some aspects associated with the redox properties of (essentially) mononuclear metal complexes. In particular, we will concentrate representatively on the redox changes of first row transition metal complexes (excluding the metallocene complexes, as they have been already discussed in Chapter 4) that give stable, or relatively stable products. A systematic and useful examination of the redox activity of organometallic complexes of transition metals dated to 1984 has appeared.1... 

In a systematical study, Golovin et al. investigated a series of metallocene derivatives in terms of their redox potentials, mass transport properties, and chemical and electrochemical stabilities in both electrochemical test cells and commercial-size AA rechargeable cells.Figure 43 shows the complete voltammetric scan of the ferrocene-containing elec-... 

It is also possible to affect H-bond strength electrochemically without the H-bonding site being an integral part of the redox couple. Good examples of this are found in the many redox-dependent receptors that utilize metallocenes, primarily ferrocene and cobaltocenium, as the redox couple. These are primarily used in ion receptors, but examples of metallocene receptors that show a significant redox dependence with neutral guests are the cobaltocenium and ferrocene diamides,... 

Electroionic signals are generated by electrochemical interconversion of a selective receptor molecule containing a redox-active group (metallocene, quinone, etc.) between states of low and high affinity for a given substrate (see Sections 6.4.1 and 8.3.1). 

Anion receptors incorporating cobaltocenium have been studied extensively due to the combination of an accessible redox couple and potential favourable electrostatic interactions of the cationic organometallic metallocene complex with anions. The first anion receptor based on this species was reported by Beer and co-workers in 1989 [6]. The macrocyclic bis-cobaltocenium receptor 1 was shown to bind (via electrostatic interaction) and to electro chemically sense bromide in acetonitrile solvent media. 

When the 7r-bonding ligand contains a sulfur or phosphorus atom, the redox properties of the corresponding complexes are much more like the corresponding metallocene. Thus the Fen(B10H10S)22- and Fen(B9H9 CHP)22 ions are more stable than the Fe(III) species. 

During the last few years we have been preparing a variety of metallocene macrocyclic molecules designed to be not only redox responsive... 

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