Redistribution and fluxionality in heteropolyoxoperoxo complexes: [PO4{M2O2(µ-O2)2(O2)2}2]3- with M = Mo and/or W

L. Salles (1) , R. Thouvenot (2) , J.-M. Brégeault (1)

1 SIEN - Systèmes interfaciaux à l'echelle nanometrique
2 CIM2 - Laboratoire de Chimie Inorganique et Matériaux Moléculaires

When peroxotetramolybdophosphate, [(n-C4H9)4N]3[PO4{Mo2O2(µ-O2)2(O2)2}2], denoted (NBu4)3PMo4, and its tungsten(VI) analogue, (NBu4)3PW4, are mixed in acetonitrile at room temperature, redistribution occurs with the formation of three mixed-addenda species [PO4{Mo4–xWxO20}]3–(x= 1–3). The temperature dependence of the phosphorus-31 NMR spectra of a 1 1 mixture and of the pure salts, (NBu4)3PMo4 or (NBu4)3PW4, shows that {MO(O2)2} species are in chemical exchange, as are the {MOp} units of certain heteropolyacids (e.g. H3[PMo12O40]·aq and H3[PW12O40]·aq). However, there is no chemical exchange between free phosphate and {MO(O2)2} species in these systems; but there is fluxional behaviour involving PMo2W2, PMo4 and PW4. This is attributed to the rapid equilibrium between isomers (PMo2W2) and to equilibrium between anionic structures with tridentate (µ-2:1-O22–) and bidentate (2-O22–) modes of coordination for the two peroxo groups of the {M2O2(µ-O2)2(O2)2} moieties.

Domaines: Catalyse

L. Salles, R. Thouvenot, J.-M. Brégeault. Redistribution and fluxionality in heteropolyoxoperoxo complexes: [PO4{M2O2(µ-O2)2(O2)2}2]3- with M = Mo and/or W. Dalton Transactions, 2004, pp.904 - 907. ⟨hal-00162378⟩