Halides redox chemistry, 516

Excision reactions are sometimes accompanied by redox chemistry. For example, dissolution of the 2D solid Na4Zr6BeCli6 in acetonitrile in the presence of an alkylammonium chloride salt results in simultaneous reduction of the cluster cores (144). Here, the oxidation product remains unidentified, but is presumably the solvent itself. As a means of preventing such redox activity, Hughbanks (6) developed the use of some room temperature molten salts as excision media, specifically with application to centered zirconium-halide cluster phases. A number of these solids have been shown to dissolve in l-ethyl-2-methylimidazolium chloride-aluminum chloride ionic liquids, providing an efficient route to molecular clusters with a full compliments of terminal chloride ligands. Such molten salts are also well suited for electrochemical studies. 

Some reactions that appear otherwise may proceed via redox processes. For example, the reaction of [E Fe(CO)4 4]3 with EX3 leads to the formation of [XE Fe(CO)4 3]2 [Eq. (257)].70 At face value this would appear to be a simple substitution of [Fe(CO)4]2 by X, but the reaction does not proceed if the halide source cannot undergo redox chemistry. Conventional [NR4]X and [PPN]X do not promote the exchange reaction while T1C13 will. 

The redox behavior of complexes of the type [Re (X)(CO)3(R-dab)] X = halide is similar to that of their polypyridine counterparts—one oxidation and two successive reductions which ultimately produce pentacoordinated [Re (CO)3(R-dab)] species [134, 136, 142]. There are, however, some remarkable differences between the redox chemistry of Re dab and polypyridine complexes (i) Oxidation [134] to [Re (X)(CO)3(R-dab)]+ is reversible and less positive (-1-0.58 V for X = Cl, R = tBu), indicating the greater stability of Re Cdab complexes and smaller involvement of E ligand orbitals in the HOMO of the Re complex, (ii) The rate of dissociation of the axial ligand after the first reduction to [Re (Br)(CO)3(R-dab )] ... 

D. Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters... 

Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters Molecular and Electronic Structure of the Group 6 Metal Halid Clusters Group 5 Metal Halide Clusters A. Synthesis of Cluster Core... 

Redox Chemistry of the Group 5 Clusters Ligand Substitution Electronic and Molecular Structure Niobium Iodide Clusters NbJJ"-Materials Chemistry Derived from Soluble Metal Halide Clusters A. Higher Nuclearity Clusters Supported Cluster Materials Charge-Transfer Salt Complexes Extended Solids Chemically Modified Surfaces... 

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