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A highly efficient method to oxidize methylarenes to their corresponding acids with a reusable Cr catalyst was developed. The reaction can be carried out in water with 1 atm oxygen and K 2 S 2 O 8 as cooxidants, proceeds under green and mild conditions, and is suitable for the oxidation of both electron-deficient and electron-rich methylarenes, including heteroaryl methylarenes, even at the gram level. The excellent result, together with its simplicity of operation and the ability to continuously reuse the catalyst, makes this new methodology environmentally benign and cost-effective. The generality of this methodology gives it the potential for use on an industrial scale. Differing from the accepted oxidation mechanism of toluene, GC-MS studies and DFT calculations have revealed that the key benzyl alcohol intermediate is formed under the synergetic effect of the chromium and molybdenum in the Cr catalyst, which can be further oxidized to afford benzaldehyde and finally benzoic acid.

A simple and efficient protocol for the formylation of amines with formic acid, catalyzed by a polyoxometalate-based chromium catalyst, is described. Notably, this method shows excellent activity and chemoselectivity for the formylation of primary amines; diamines have also been successfully employed. Importantly, the chromium catalyst is potentially non-toxic, environmentally benign and safer than the widely used high valence chromium catalysts such as CrO 3 and K 2 Cr 2 O 7 . The catalyst can be recycled several times with a negligible impact on activity. Finally, a plausible mechanism is provided based on the observation of intermediate and control experiments.

Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H 2 O 2 as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH 4 ) 3 [FeMo 6 O 18 (OH) 6 ], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.

A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.

Correction for 'Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide-alkyne cycloaddition reaction: their synthesis and structural characterization' by Hongli Jia et al., Dalton Trans., 2018, 47, 577-584.

In this work, we confirmed that the copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction is an effective method for the organic-functionalization of polyoxometalates (POMs). Herein, for the first time, four novel 1,2,3-triazole functionalized polyoxovanadate (POV) organic-inorganic hybrids, (Bu 4 N) 2 [V 6 O 13 {(OCH 2 ) 3 C 5 H 6 N 3 O} 2 ]·1.5CH 3 CN 2, (Bu 4 N) 2 [V 6 O 13 {(OCH 2 ) 3 C 7 H 8 N 3 O 2 } 2 ]·2CH 3 CN 3, (Bu 4 N) 2 [V 6 O 13 {(OCH 2 ) 3 C 11 H 10 N 3 } 2 ] 4 and (Bu 4 N) 2 [V 6 O 13 {(OCH 2 ) 3 C 10 H 7 N 3 Cl} 2 ] 5 were prepared through the CuAAC reaction using the azide functionalized hexavanadate, (Bu 4 N) 2 [V 6 O 13 {(OCH 2 ) 3 CCH 2 N 3 } 2 ]·2.5CH 3 CN 1, as the precursor, where CuI was used as the catalyst and N,N-diisopropylethylamine (DIPEA) as a stabilizer for Cu I . All the four compounds were structurally and compositionally characterized by single-crystal X-ray diffraction, elemental analyses, powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), 1 H NMR, ESI-MS, UV-Vis and thermogravimetric analysis (TGA).

A new synthetic approach to tri-substituted trisalkoxy-hexavanadate clusters containing different organic groups was developed in this work. Four mixed-valence or fully reduced POV hybrids were synthesized and structurally characterized, including an amino-containing derivative of hexavanadate, Na 2 [VVO 10 {NH 2 C(CH 2 O) 3 } 3 ] (1). Furthermore, a novel mixed-valence POV hybrid was prepared via the amidation of 1, indicating that 1 can be used as an excellent building block for the design and synthesis of mixed-valence POV functional materials.

A reaction strategy for the post-functionalization of hexavanadate derivatives is presented herein. In this study, five polyoxovanadate-based organic-inorganic hybrids TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOO(CH 2 ) 15 CH 3 } 2 ] (2), TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOO(CH 2 ) 8 CH[double bond, length as m-dash]CH 2 } 2 ] (3), TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOOCH 2 CF 3 } 2 ] (4), TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOO(CH 2 CH 2 O) 3 CH 3 } 2 ] (5), and TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOO(CH 2 ) 12 OH} 2 ]·2CH 3 CH 2 OH (6) were successfully synthesized via esterification of carboxylic acid groups-containing TBA 2 [V 6 O 13 {(OCH 2 ) 3 CCOOH} 2 ] (1) with five alcohols possessing different functional groups. These hybrids were characterized by single crystal X-ray diffraction, IR, ESI-MS, 1 H and 13 C-NMR spectroscopies, and elemental analysis. Moreover, the formation of large vesicles was observed in a mixed solution of compound 2 due to its surfactant-like structure.

A class of monoorganoimido-substituted hexamolybdates containing a pyridine group have been firstly synthesized. Furthermore, a reaction protocol of alkylation based on the resulting pyridine-functionalized hexamolybdates has been developed, with which a type of zwitterionic clusters has been successfully obtained.

An efficient protocol for post-functionalization of organo-imido polyoxometalates is developed via creating a remote tertiary “N” atom over the surface of organo-imido hexamolybdates and subsequently post-functionalizing it with the help of allyl or alkyl halides to afford stoichiometric, “in situ” crystalline products at moderate temperatures. The parent organo-imido product 2 and post-functionalized crystalline products 3 and 4 are compared for their solid state structures. The post-functionalization protocol introduced here allows the inclusion of the desired functional groups as remote reactive organic groups over a POM's highly negative surface. The in situ crystallization of post-functionalized products further guarantees an 100% purity of final products, along with 95% yield.

Three single-sided, triol-functionalized Anderson POM hybrids were successfully synthesized. With suitable solvents and the effect driven by common-ion synergy, enantiopure crystals were obtained when the spontaneous resolution of enantiomers occurred upon crystallization. The chirality of POM-organic hybrids was confirmed by single-crystal X-ray diffraction and solid-state CD spectrum. A reversible, spontaneous resolution process for POM-based inorganic-organic hybrids was observed in this work.

Polyoxometalate-based organic-inorganic hybrids were synthesized by direct modification of the parent Anderson cluster with both the traditional tripodal ligand, CH3C(CH2OH)3, and a novel one containing a carboxyl group, CH3C(CH2OH)2(COOH), which was inaccessible from the traditional self-assembly protocol.

Bi-alkylimido functionalization of hexamolybdates has been developed and several novel di-substituted alkylimido hexamolybdates with n-butyl, cyclohexyl and tert-butylamines as the imido-releasing reagents have been synthesized in reasonable yields. Their structures have been characterized by elemental analysis, IR, UV-Vis, and ESI mass spectrometry. Moreover, the structures of [Mo(6)O(17)(NCy)(2)](2-) and [Mo(6)O(17)(NCMe(3))(2)](2) have been determined by single-crystal X-ray diffraction techniques. It is notable that the compound (Bu(4)N)(2)[Mo(6)O(17)(NCy)(2)] crystallizes in polar space group Fdd2 with potential ferroelectricity. In addition, theoretical investigation of the reactivity and regioselectivity of bi-alkylimido functionalization has also been conducted. The calculation results show that more energy is required for the bi-functionalization process than for the mono-substitution process, and that the cis-bi-functionalization is the kinetically favored process while trans-[Mo(6)O(17)(NR)(2)](2-) is the thermodynamically favored product.

The chemistry of organoimido derivatives of polyoxometalates (POMs) has received increasing interest. In recent decades, a great development of the synthetic chemistry of organoimido derivatives of POMs using different imido-releasing reagents has taken place, particularly the novel DCC-dehydrating protocol to prepare organoimido derivatives of POMs was developed recently by us and co-workers. Organoimido substituted POMs as valuable building blocks can construct novel nanostructured organic-inorganic hybrid molecular materials in well-developed common organic synthesis methods, such as Pd-catalyzed carbon-carbon coupling and esterification. Therefore, the reactive chemistry of organoimido derivatives of POMs stands for the fascinating future of the chemistry of organoimido derivatives of POMs.

Three novel rigid-rod conjugated organic-POM hybrids (1, 2 and 3) containing pendant amino terminus, with different rod lengths and different substituents on the rod, have been respectively synthesized via one-pot reaction of hexamolybdate and the corresponding aromatic diamine (for 1 and 2) and reaction of octamolybdate and the corresponding aromatic diamine dihydrochloride (for 3) with N,N'-dicyclohexylcarbodiimide (DCC) as a dehydrating agent. These complexes have been characterized by UV/Vis, IR, (1)H NMR, ESI and single-crystal X-ray diffraction techniques. The influences of the rod length and substituents on the properties of these compounds have been systematically investigated, which provide necessary information for further preparations of complicated hybrid materials via reactions with pendant amino groups., (This journal is © The Royal Society of Chemistry 2011)

Monofunctionalized alkylimido derivatives of hexamolybdate, (Bu(4)N)(2)[Mo(6)O(18)( identical withN-R)] (R = methyl, Me; ethyl, Et; n-propyl, n-Pr; i-propyl, i-Pr; n-butyl, n-Bu; t-butyl, t-Bu; cyclohexyl, Cy; n-hexyl, Hex; and n-octadecyl, Ode), have been prepared in high purity and good yield by the reaction of [Bu(4)N](4)[alpha-Mo(8)O(26)] with appropriate aliphatic amine hydrochlorides in anhydrous acetonitrile, using N,N'-dicyclohexylcarbodiimide (DCC) as the dehydrating agent. Eight compounds have been determined by single crystal X-ray diffraction analysis and all compounds have been studied with (1)H-NMR, IR, UV-vis, ESI mass spectrometry and cyclic voltammetry. A structural and (1)H-NMR study show beta hydrogen atoms of those alkylimido derivatives of hexamolybdate have strong Brønsted acidity compared to the hydrogen atoms in other positions.

Three novel mono-functionalized arylimido derivatives of hexamolybdate bearing the strongest electron-withdrawing nitro group, (Bu(4)N)(2)[Mo(6)O(18)([triple bond]NAr)] (1, 2 and 3), have been synthesized for the first time by an improved reaction of octamolybdate ion and 3-nitroaniline hydrochloride, 2-methyl-4-nitroaniline hydrochloride and 2-methyl-5-nitroaniline hydrochloride respectively with DCC (N,N'-dicyclohexylcarbodiimide) as a dehydrating agent. Complete assignments were achieved for the title compounds by elemental analysis, IR, (1)H NMR, UV/visible and single-crystal X-ray diffraction analyses. The preliminary antitumor activity test indicated that the title compounds have some effects on the cellular growth inhibition of K562 cells.