“…Thus, binding of dioxygen results in the characteristic heptacoordination for the peroxidized W atoms, which exhibit the pentagonal-bipyramidal geometry of other oxomonoperoxo complexes of Mo and W, as illustrated in Figures and . The O−O distances observed for the dioxygen fragments are 1.41 and 1.44 Å, which do not differ significantly from the usual value around 1.45 Å seen in other peroxo complexes. , Also the W−O distances (1.89−1.96 Å) and O−W−O angles (42.9° and 43.4°) involving the peroxidic O atoms (see Table ) are similar to those found in other peroxotungstates and molybdates previously reported (1.81−2.00 Å and 44.2−44.7°, respectively). 12b, 1 ORTEP view of the X-ray crystallographically determined structure and numbering scheme of the β 3 -[Co 2+ W 11 O 35 (O 2 ) 4 ] 10- anion. Thermal ellipsoids at 30% probability level.…”
Reactions of hydrogen peroxide with several lacunary polyoxometalates of the 1:11 series, XW11O39
m
-
(X = Co3+, Ga3+, Fe3+, Si4+, and P5+), are reported. Synthetic pathways to new polyoxotungstates incorporating
dioxygen moieties (peroxo and/or superoxo) are developed. The key step involves treating lacunary precursors
with H2O2 in strongly buffered aqueous solutions. Upon reaction of H2O2 with α-[Co3+W11O39],
- (a) the
central tetrahedral Co3+ is reduced to Co2+ and (b) each of the four unshared oxygens surrounding the vacancy
are replaced by a peroxide group, yielding salts of the tetraperoxide anion β3-[(Co2+O4)W11O31(O2)4]10- (1).
These results are unequivocally established by a combination of elemental analysis, spectroscopy (UV−Vis−near-IR and IR), magnetic moment determination, and complete X-ray crystal structure analysis of (NH4)9K[(Co2+O4)W11O31(O2)4]·5H2O. The dioxygen O−O bonds are 1.41 and 1.44 Å, typical of peroxo complexes.
Salts of 1 are excellent stereoselective catalysts for the oxidation/epoxidation by H2O2. Reaction of
2-cyclohexenol with H2O2 catalyzed by 1 yields cis- and trans-2,3-epoxycyclohexen-1-ol (59.3% and 3.6%,
respectively) and 2-cyclohexen-1-one (28.3%). According to ESR and IR spectroscopic results, the reaction of
H2O2 with other lacunary XW11O39
m
- anions (X = P5+, Si4+, Ga3+, and Fe3+) proceeds by a different mechanism
which involves the loss of heteroatom and formation of an isopolytungstate containing superoxo moieties (g
1
= 2.039, g
2 = 2.014, g
3 = 2.009; ν0
-
0 = 1040 and 1060 cm-1).
“…Thus, binding of dioxygen results in the characteristic heptacoordination for the peroxidized W atoms, which exhibit the pentagonal-bipyramidal geometry of other oxomonoperoxo complexes of Mo and W, as illustrated in Figures and . The O−O distances observed for the dioxygen fragments are 1.41 and 1.44 Å, which do not differ significantly from the usual value around 1.45 Å seen in other peroxo complexes. , Also the W−O distances (1.89−1.96 Å) and O−W−O angles (42.9° and 43.4°) involving the peroxidic O atoms (see Table ) are similar to those found in other peroxotungstates and molybdates previously reported (1.81−2.00 Å and 44.2−44.7°, respectively). 12b, 1 ORTEP view of the X-ray crystallographically determined structure and numbering scheme of the β 3 -[Co 2+ W 11 O 35 (O 2 ) 4 ] 10- anion. Thermal ellipsoids at 30% probability level.…”
Reactions of hydrogen peroxide with several lacunary polyoxometalates of the 1:11 series, XW11O39
m
-
(X = Co3+, Ga3+, Fe3+, Si4+, and P5+), are reported. Synthetic pathways to new polyoxotungstates incorporating
dioxygen moieties (peroxo and/or superoxo) are developed. The key step involves treating lacunary precursors
with H2O2 in strongly buffered aqueous solutions. Upon reaction of H2O2 with α-[Co3+W11O39],
- (a) the
central tetrahedral Co3+ is reduced to Co2+ and (b) each of the four unshared oxygens surrounding the vacancy
are replaced by a peroxide group, yielding salts of the tetraperoxide anion β3-[(Co2+O4)W11O31(O2)4]10- (1).
These results are unequivocally established by a combination of elemental analysis, spectroscopy (UV−Vis−near-IR and IR), magnetic moment determination, and complete X-ray crystal structure analysis of (NH4)9K[(Co2+O4)W11O31(O2)4]·5H2O. The dioxygen O−O bonds are 1.41 and 1.44 Å, typical of peroxo complexes.
Salts of 1 are excellent stereoselective catalysts for the oxidation/epoxidation by H2O2. Reaction of
2-cyclohexenol with H2O2 catalyzed by 1 yields cis- and trans-2,3-epoxycyclohexen-1-ol (59.3% and 3.6%,
respectively) and 2-cyclohexen-1-one (28.3%). According to ESR and IR spectroscopic results, the reaction of
H2O2 with other lacunary XW11O39
m
- anions (X = P5+, Si4+, Ga3+, and Fe3+) proceeds by a different mechanism
which involves the loss of heteroatom and formation of an isopolytungstate containing superoxo moieties (g
1
= 2.039, g
2 = 2.014, g
3 = 2.009; ν0
-
0 = 1040 and 1060 cm-1).
“…Several attempts have been data have yet been found, but it should be pointed out that dioxygen-molybdenum complexes are known to exist. 13 Introduction Hydrazinium ion is known to be a very powerful reducing agent. 1 The thermodynamic reducing strength of hydrazine is dependent on the nitrogen species to which hydrazine is oxidized.…”
“…Baerwald (1885) probably reported the first peroxidomolybdate. Stomberg et al have prepared a range of peroxidomolybdates and obtained crystal structures of these species, see: Larking & Stomberg (1970, 1972; , 1997a; Persdotter et al (1986a,b,c); Stomberg (1968Stomberg ( , 1969Stomberg ( , 1970Stomberg ( , 1988aStomberg ( ,b, 1992Stomberg ( , 1995; Stomberg & Trysberg (1969); ; Trysberg & Stomberg (1968, 1981. The versatile MoO 6 octahedron building block [see: Pope & Mü ller (1991); Chen & Zubieta (1992)] results in an exceptionally large family of polyoxidomolybdates, see: Michailovski & Patzke (2006).…”
The title compound (NH4)4[Mo8O24(O2)2(H2O)2]·4H2O, consists of an octamolybdate cluster with a crystallographic centre of symmetry. The clusters pack in a cubic close packing arrangement defining channels containing water molecules and ammonium cations, which exhibit hydrogen bonding with neighbouring clusters. Hydrogen bonding also exists between the coordinated water molecules of one cluster with one of the O atoms of the peroxido fragment in a neighbouring cluster.
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