ChemInform Abstract: Synthesis, Characterization, and Catalysis of β₃‐ [(Co^(II)O₄)W₁₁O₃₁ (O₂)₄]^10‐, the First Keggin‐Based True Heteropoly Dioxygen (Peroxo) Anion. Spectroscopic (ESR, IR) Evidence for the Formation of Superoxo Polytungstates.

Abstract

Synthesis, Characterization, and Catalysis of β 3 -[(Co (II) O 4 )W 11 O 31 (O 2 ) 4 ] 10− , the First Keggin-Based True Heteropoly Dioxygen (Peroxo) Anion. Spectroscopic (ESR, IR) Evidence for the Formation of Superoxo Polytungstates.-Compounds (IV) represent the first true heteropolymetallates containing dioxo (peroxo) moieties in a Keggin-related structure. The structure is unequivocally established by a combination of spectroscopic methods and X-ray analysis of the mixed salt (IVb) (space group P2 1 /m, Z = 2). Salts (IV) prove to be effective catalysts for the oxidation/epoxidation of alcohols and olefins with H 2 O 2 . Similar reaction of H 2 O 2 with other lacunary XW 11 O 39 m− anions (X: Si IV , P V , Ga III , Fe III ) yields a novel isopolytungstate containing superoxo moieties, whose structure and composition is independent of the heteroatom present in the lacunary precursor.

Unveiling the Active Surface Sites in Heterogeneous Titanium-Based Silicalite Epoxidation Catalysts: Input of Silanol-Functionalized Polyoxotungstates as Soluble Analogues

“…41,42,43 In the case of hybrids of POMs, both base-and acid-catalyzed hydrolysis may lead to the release of silanol arms and the generation of cis-W(=O) 2 units (Scheme S2). 44 The latter have been proven to react 45,46 The involvement of lacunary species in POM-catalyzed oxidation reactions with hydrogen peroxide is thus most commonly accepted. Some rare examples of nonlacunary heteropolyoxometalate stable towards H 2 O 2 have been reported, among which we can mention the titanium-substituted heteropolyoxotungstates reported independently by the groups of Kholdeeva, 47,48 Mizuno, 49,50 and Nomiya.…”