Studies on polyoxo- and polyperoxo-metalates. Part 1. Tetrameric heteropolyperoxotungstates and heteropolyperoxomolybdates

Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

“…Some authors found good activity in epoxidation [154,156], while others found no activity at all [125,155]. The reasons for that have become clearer in the light of the recent findings [112,133,137,[157][158][159]. First, several 31 P NMR studies implicated that most POMs are not stable toward high excesses of H 2 O 2 and, in fact, they act as precursors of the true catalyst, Venturello complex …”

Dititanium‐Containing 19‐Tungstodiarsenate(III) [Ti2(OH)2As2W19O67(H2O)]8−: Synthesis, Structure, Electrochemistry, and Oxidation Catalysis

“…[3i, 4] It is worth [19,[21][22][23] The resistance towards H 2 O 2 is known to increase with increasing POM charge. [19] To ascertain correct interpretation of the catalytic results, we addressed the question of stability of 1 in the presence of an excess of H 2 O 2 .…”

Another Example of the Instability of a Keggin‐Type Heteropolyanion in the Presence of Aqueous Hydrogen Peroxide: From [AsW12O40]3– to Low‐Nuclearity Oxoperoxotungstates – Crystal Structure of [(nHex)4N]3[AsO4{W2O2(μ‐O2)2(O2)2}2]

“…Attempts to measure the Raman spectra of 1, 2 and 6 in a benzene solution were unsuccessful, [42] but the solid state and acetonitrile solutions show common features in the 500-1000 cm -1 region, which suggests that the structures of the anions of 4, 5 and 6 are maintained in some organic solvents (here acetonitrile) at room temperature, as proposed in a preliminary structural study. [14] The IR and Raman spectra of 6 are presented in Figure 2 and the attributions of the main infrared and Raman vibrations are given in Table 2.…”

“…[11,30,42,43,54] The Arquad 2HT ® salts of complexes "AsW 4 " and "AsW 2 " are active precursors and catalysts in olefin oxidation, and form epoxides in the range 20-60°C in two-phase "H 2 O 2 / H 2 O/CHCl 3 or toluene" systems under phase-transfer catalysis (PTC) conditions (see Table 3, Entries 2 to 4). They transfer active oxygen to (R)-(+)-limonene to mostly give the monoepoxides, which are known to be acid-sensitive.…”

“…Salts of the anion have been prepared by several groups; [11][12][41][42][43] despite many attempts to show that 1, 2 and 6 are isomorphous, it was previously difficult to isolate single crystals of 6 suitable for X-ray measurements. The profiles of the Raman and infrared spectra of 6 are compared with those of tetran-butylammonium (µ-hydrogenoarsenato)bis(µ-peroxo)bis-(oxoperoxotungstate)(2-) (4) [14] and with those of the methylarsenato analogue (5).…”