Polyoxomolybdate compounds

An important consideration in applying Mo NMR to practical problems is the ability of the technique to distinguish between M0O4 and MoOe units. Mo NMR studies of a series of isotopically enriched polyoxomolybdate compounds similar to those used as hydrodesulphurisation catalysts showed that at a relatively low field (9.4 T) and low... 

More recently, some other compounds containing polyoxometallates coordinated to Bi were reported by U. Kortz et al., who investigated the interactions of amino acids with polyoxomolybdates in the presence of inter alia Bi +-ions [55,56]. A series of ionic compoimds with anions of the general formula [XM06O21 (amino acid)3] (X = As , Sb , Bi ) were prepared. In case of the bismuth derivatives the amino acids HOOC(CH2) NH2 (n = 1, 2, 3) and L-HOOCCH[(CH2)4NH2]NH2 were reacted with Na2Mo04, Bi203 and KCl in an aqueous medium (Eq. 8). 

Figure 15. Crystal structure of Compound 121 illustrating the importance of hydrogen bonding between cyclopentadienyl protons and the negatively charged polyoxomolybdate anion. [Reprinted from J. Organomet. Chem.. 488. C4 (1995) P. L. Veya and J. K. Kochi, Structural and spectral characterization of novel charge transfer salts of polyoxometalates and the cationic ferrocenyl donor. Copyright 1995, with kind permission from Elsevier Science SA, Lausanne, Switzerland]...

Flash photolysis studies have been carried out on these systems to try and determine the compounds that are formed in the initial steps of the photoreaction. For the polyoxomolybdate MoyO, no long-lived intermediates are observed, and no significant quantities of hydroxyl radicals are observed, even in the presence of 2-propanol. These observations are best interpreted on the basis of the initial formation of a mixed-valent polymolybdate intermediate that has an oxide radical functioning as a ligand. Such a species can result from LMCT excited states that have charge transfer character due to the transition from a to a... 

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