Reduction of the Phosphododecamolybdate Ion by Phosphonium Ylides and Phosphanes

Abstract

The reaction of phosphonium ylides with [PMo12O40]3− consists of successive single electron transfers leading to the formation of the 1e‐ and 2e‐reduced polyoxomolybdates [PMo12O40]4− and [PMo12O40]5−. The ylide is converted into the corresponding phosphonium cation via a radical‐cation intermediate. The reaction of phosphanes follows the same pathway but subsequent reactions with residual water produce protons which induce the disproportionation of [PMo12O40]4−. Authentic samples of heteropoly blues in different protonation states have been obtained from the reaction of phenyllithium with [PMo12O40]3− and subsequent protonation with triflic acid. On the basis of electrochemical and spectroscopic data, the reaction product of [PMo12O40]3− with triphenylphosphane, which has been previously described as the oxygen‐deficient species [PMo12O39]3−, is reformulated as [H2PMo12O40]3−.

Synthesis and crystal structure of a mixed valence heteropoly green compound, (PPh4)4[PMo12O40], and its use as a catalyst in olefin epoxidation

“…Meiklejohn et al [20] reported the same salt, obtained by chemical reduction as a 'dark green blue' product characterized only by analytical and spectroscopic data. Artero et al [21] isolated (PPh 4 ) 4 [PMo 12 O 40 ], the asolvate of the one electron reduced product we are reporting here, and stated that their product was blue-coloured. Characterization was limited to analytical, IR and UV-Vis data.…”

“…Two-and four-electron reduced anions with X = P have been structurally characterized [12,15]. One electron reduced species are very rare [16][17][18][19][20][21] and X-ray structure analysis is so far limited to the blue (Bu 4 N) 4 [PMo 12 O 40 ] Á 2DMF Á H 2 O, obtained by photochemical reduction [19] of the d 0 Keggin ion. Meiklejohn et al [20] reported the same salt, obtained by chemical reduction as a 'dark green blue' product characterized only by analytical and spectroscopic data.…”

Electron Transfer to a Phosphomolybdate Monolayer on Glassy Carbon: Ambivalent Effect of Protonation

“…As mentioned above, the CVs of POMs in solution are strongly sensitive to the presence of small cations or protons and to their degree of association with the POM-reduced forms. 66,67,49 The behavior of Keggin anions in acidified aqueous, mixed aqueous/organic, and acetonitrile solutions has been extensively studied 68,62 and accounted for in terms of protonation of their reduced forms, according to their relative basicities. 50,51 For nonsubstituted POMs, one-electron, one-proton (or two-electron, two-proton) successive steps are generally considered.…”

Bis{tris[3-(2-pyridyl)-1H-pyrazole]nickel(II)} dodecamolybdo(V,VI)phosphate hexahydrate

“…For polyoxometalates modified with amines, see ;. For the structures of other reduced heteropolyanions with composition [PMo 12 O 40 ] 4À , see: Artero & Proust (2000); Kurmoo et al (1998). ; Niu et al (1999).…”

“…of a complex [Ni(C 8 Artero & Proust (2000); Kurmoo et al (1998);Niu et al (1999). The employed organic ligand appears to adjust the pH value, and additionally supplies reducing electrons, which is a commonly observed feature of hydrothermal syntheses when organic amines are used to prepare various hybrid materials, zeolites or metal phosphates (Yang et al, 2003).…”