Molybdophosphate heteropoly blues: Electron-transfer reactions in aqueous solutions as studied by NMR

Spectroscopic Study of the Behavior of Mo(VI) and W(VI) Polyanions in SulfuricPhosphoric Acid Mixtures

“…Three sharp signals, at about -3.7 (B), -1.5 (C), and -0.3 (D) ppm, were observed at 0.06 mol•kg -1 H 2 SO 4 (Mo_std-1, TableS2). These signals are consistent with those previously reported for 1~2 mmol•L -1 H 3 PMo 12 O 40 in 0.02 mol•L -1 HCl(aq)[23]. Signal B is similar to that of crystalline H 3 PMo 12 O 40 dissolved in water[24,25] and thus is assigned to the PMo 12 O 40 3-Keggin anion.…”

“…Signal B is similar to that of crystalline H 3 PMo 12 O 40 dissolved in water[24,25] and thus is assigned to the PMo 12 O 40 3-Keggin anion. Signals C and D are alkaline hydrolysis products of the Keggin anion[23,26]: the lacunary derivatives PMo 11 O 39 7and PMo 9 O 34 9-, respectively[27]. Peak C is also close to that of γ-P 2 Mo 18 O 62 6-[25,28], however, this species can be eliminated on kinetic grounds[23].With increasing acidity, the three signals related to the Keggin anion or its derivatives weaken and a broad line appears at ~0 ppm, corresponding to the H 3 PO 4 signal.…”

“…Signals C and D are alkaline hydrolysis products of the Keggin anion[23,26]: the lacunary derivatives PMo 11 O 39 7and PMo 9 O 34 9-, respectively[27]. Peak C is also close to that of γ-P 2 Mo 18 O 62 6-[25,28], however, this species can be eliminated on kinetic grounds[23].With increasing acidity, the three signals related to the Keggin anion or its derivatives weaken and a broad line appears at ~0 ppm, corresponding to the H 3 PO 4 signal. At 1.0 mol•kg -1 H 2 SO 4 ; Mo_std-4, TableS2), only the signal of H 3 PO 4 can be observed, indicating that the multinuclear ions have…”

Synthesis, Characterization and Catalytic Activity of NHC Gold(I) Polyoxometalate Complexes

“…At this stage, the catalyst has undergone color change from green to deep blue, hinting at the possible formation of either molybdenum blues or either reduced forms of the Keggin's anion . Its 31 P NMR spectra exhibits the expected signal of the [PMo 12 O 40 3− ] anion at −3.6 ppm, along with two sharp upfield signals at −5.9 and −12.9 ppm supporting the presence of reduced POMs, such as [PMo 12 O 40 5− ] and [PMo 12 O 40 7− ] anions . The 1 H and 13 C NMR spectra confirm the presence of NHC fragments without providing any clear information as to the gold cation's environment, due to low concentration.…”

Transition metal-substituted Keggin-type polyoxometalates as catalysts for adipic acid production

“…The catalytic process of cyclohexanone oxidation by hydrogen peroxide in the presence of POM is composed of three steps. The first step corresponds to the substrate oxidation by [25]. In these latter species, there is a departure of both molybdenum and oxygen atoms (Eq.…”