Complexes organometallic redox chemistry

The redox properties of thallium are important in preparative organic and organometallic/inorganic chemistry. For this reason, studies of redox behavior and the thermodynamics and kinetics of complexing processes are likely to remain relevant. The employment of the TF ion as a probe for in biological systems will no doubt continue, because of the easy detection of the former. For the same reason, thallium(III) can be used as a representative for several other metal ions in solution. 

The characterization and utilization of photochemical processes are rapidly developing into one of the major areas of activity in modern inorganic and physical chemistry. In the past, the photochemistry of classical metal coordination complexes has received the greatest amount of attention, but recently the photochemistry of organometallic compounds has attracted notice In particular, the photochemistry and photophysics of uranyl compounds have been investigated for more than four decades and a great deal has been learned about the primary photoprocesses and the photo-induced reaction mechanisms displayed by these complexes (.3,4). The popularity of uranyl compounds in photochemical studies is derived from their ready availability and stability, their facile redox chemistry and photosensitivity and their rich excited state chemistry. Since current reviews of uranyl photochemistry are expected to appear in the near future, vide infra, further discussion of this topic here will be limited. 

Complex chemistry of cyclophanes links the two best examined two-layered molecules of organic and organometallic chemistry, namely [22 ]para-cyclophane and ferrocene. The rich redox chemistry of ruthenium, cobalt, rhodium and iridium therefore provides a basis for constructing polymeric structures, of which some oligomeric building units are already known. 

Figure 7 illustrates the electrochemial redox chemistry in acetronitrile for several coordination complexes of iron [Fe (MeCN)4, Fe CL, and Fe (acac)s (acac = acetylacetonate)] in relation to that for two iron organometallics [Fe (Cp)2 and Fe (CO)s (iron-pentacarbonyl) both stable 18-electron systems]. In MeCN, Fe (MeCN)4" is the only charged species of the group. It is reversibly oxidized (II/III couple E1/2, -I-1.6 V vs SCE). The uncharged Fe Cb molecule is reversibly reduced (Ill/n couple Ei/2, -1-0.2 V vs SCE) to giveFe Cl, which is reduced by an irreversible two-electron process to iron metal (Ep,c -L5 V vs SCE). The more basic Fe (acac)3 molecule is reversibly reduced (ni/n couple Ei/2, -0.7 V vs SCE), but does not exhibit a second reduction peak. The III/II reduction potentials for these three coordination complexes are a measure of their relative electrophilicity (Lewis acidity). 

An account of the redox chemistry of binuclear palladium complexes and the role of binuclear intermediates in Pd-catalysed oxidation reactions has been provided. Stoichiometric organometallic studies of the oxidation of binuclear Pd(II) complexes to binuclear Pd(III) complexes and subsequent C-X reductive elimination from the resulting binuclear Pd(III) complexes, which confirmed the viability of C-X bond-forming reactions mediated by binuclear Pd(III) complexes, has been described. The effect of ligand modification on the structure and reactivity of binuclear Pd(III) complexes has been presented to highlight the impact that ligand structure can exert on the structure and reactivity of binuclear Pd(III) complexes." ... 

Barranco, E.M., Crespo, O., Gimeno, M.C., Jones, P.G., Laguna, A. and Villacampa, M.D. (1999) Synthesis, structure and redox behaviour of gold and silver complexes with 3-ferrocenylpyridine. Journal of Organometallic Chemistry, 592, 258. 

Binuclear and polynuclear compounds with direct metal-metal interaction constitute a large class of transition metal complexes which play an important role also in organometallic chemistry. Generally, the frontier orbitals of these compounds are engaged in metal-metal bonding. Consequently, redox processes affect the metal-metal interaction. The same is true for the luminescence of such complexes since it involves also thg frontier orbitals. The binuclear complex Pt2(pop) 36) (pop = diphosphonate) and... 

Based upon analogies between surface and molecular coordination chemistry outlined in Table 1, we have recently set forth to investigate the interaction of surface-active and reversibly electroactive moieties with the noble-metal electrocatalysts Ru, Rh, Pd, Ir, Pt and Au. Our interest in this class of compounds is based on the fact that chemisorption-induced changes in their redox properties yield important information concerning the coordination/organometallic chemistry of the electrode surface. For example, alteration of the reversible redox potential brought about by the chemisorption process is a measure of the surface-complex formation constant of the oxidized state relative to the reduced form such behavior is expected to be dependent upon the electrode material. In this paper, we describe results obtained when iodide, hydroquinone (HQ), 2,5-dihydroxythiophenol (DHT), and 3,6-dihydroxypyridazine (DHPz), all reversibly electroactive... 

ArmentroutPB (1999) Gas-Phase Organometallic Chemistry. 4 1-45 Astruc D, Daniel M-C, Ruiz J (2006) Metallodendritic Exo-Receptors for the Redox Recognition of Oxo-Anions and Halides. 20 121-148 Aubert C, Fensterbank L, Gandon V, MalacriaM (2006) Complex Polycyclic Molecules from Acyclic Precursors via Transition Metal-Catalyzed Cascade Reactions. 19 259-294... 

---