Cyclic voltammetry organometallic

Mixed-metal dendrimers containing up to 6 Pt(IV)-based organometallic species in the branches and 12 peripheral ferrocene units (8) have recently been synthesized and their electrochemical behavior investigated [13]. As in the previously discussed examples, multi-electron reversible oxidation processes, assigned to the equivalent, non-interacting ferrocene units, have been observed. The authors point out that cyclic voltammetry is a powerful tool to support the structure of the dendrimers containing ferrocene units. 

M. Tilset. Derivative Cyclic Voltammetry Applications in the Investigation of the Energetics of Organometallic Electrode Reactions. In Energetics of Organometallic Species, J. A. Martinho Simoes, Ed. NATO ASI Series C, Kluwer Dordrecht, 1991 chapter 8. 

Scheme 3 accounts for the various products formed, and it is consistent with known transformations in organometallic chemistry. In the first step, CO2 is reduced in a proton-coupled two-electron process to form adsorbed CO. That CO is an intermediate in the reduction of CO2 to hydrocarbons is supported by the following observations. (1) Reduction of CO at copper electrodes under the same conditions gives a similar distribution of hydrocarbon products. Reduction of formate, on the other hand, gave no hydrocarbon products [98, 102]. (2) CO on the electrode surface could be detected by cyclic voltammetry measurements. Fourier transform... 

All C60 adducts have low-lying LUMOs that can easily be populated by electrochemical methods. For C60 itself, six reduction couples have been observed by cyclic voltammetry (CV) or square-wave voltammetry (SWV), and as many as four reduction couples have been found for many organometallics (9,84). Most of the studies have been performed in thf or acetonitrile at lower temperatures, which increases the size of the potential window. Table VII lists the half-wave potentials for some metal complexes, and Fig. 7 shows the cyclic voltammogram for [Co(NO)(PPh3)2(i72-C60)]. 

This chapter concerns the study of electrode reaction mechanisms of inorganic and organometallic complexes. The emphasis is on proper use of experimental measurables from cyclic voltammetry for diagnosis of common mechanisms such as E, EC, CE, and ECE reactions. We employ the standard designation of electron transfer (et) reactions as E, and other chemical reactions as C. In practice, mechanistic studies make use of an array of electrochemical and other physical and chemical methods, but space limitations restrict our attention to the powerful and versatile technique of cyclic voltammetry (CV). If necessary, the reader may review the fundamentals of this technique in Chapter 3. 

Thiocyanate — Thiocyanate (SCN") - anions can be found in industrial wastewaters, pesticide residues, and organism metabolites. They can be determined by - ion-selective electrodes based on a variety of carriers such as organometallic compounds and metal-loporphyrin derivatives. Also, SCN- forms - complexes with metal -> ions (e.g., Ag(SCN)y) and influences the responses of metal ions in -> cyclic voltammetry. 

TABLE 9. Cyclic voltammetry data (V) of organometallic complexes... 

The acidity of the coordinated water in organometallic aquocomplexes varies over a large range. In aqueous solutions pH potentiometry is one of the most precise methods of determining the acid dissociation constants, K3, for the organome-tal ions. Several stable oxidation states of the transition metal ions in organometallic compounds can exist in water. Cyclic voltammetry gives information on the reversibility of the oxidation/reduction processes. 

Electrochemical techniques have also been applied to determining metal-metal bond energies in dinuclear organometallic molecules (44). Using a combination of redox equilibration experiments with reagents of known potentials and fast scan cyclic voltammetry, it is possible to obtain E° data for the kinds of reactions shown in Equations 33 and 34, respectively. The result is the free energy (but not the... 

In this chapter, the application of electrochemical techniques in organometallic chemistry will be presented with specific focus on utilization of electrode potential data to extract thermodynamic quantities pertaining to metal-ligand bonding energetics. Many readers may be unfamiliar with the electrochemical methods, and therefore the most widely used technique to obtain the required electrode potential data - cyclic voltammetry (CV) - will be briefly described. The derived bond energy data will be no better than the underlying electrode potential data, and therefore some issues which, in the author s view, are particularly relevant to ensure that data are obtained as accurately and correctly as possible will be discussed. For a more in-depth discussion of CV and other electrochemical techniques, the reader is referred to selected textbooks and reviews. 

Thermodynamic cycles involving standard electrode potentials obtained by cyclic voltammetry have also been used to provide thermochemical information on organometallic compounds. This so-called electrochemical method leads to Gibbs energies of reaction in solution, from which bond dissociation enthalpies may be derived using a number of auxiliary data that are often estimated. For example, the derivation of a metal-hydrogen bond dissociation enthalpy in an L MH species requires (i) an estimate of the reduction potential of in the same solvent where the experiments were carried out (ii) an estimate of the solvation entropies of L MH, L M, and H and (iii) the knowledge of the pK of... 

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