Vladimir P. Fedin

Hybrid Polyoxotungstate/MIL-101 Materials: Synthesis, Characterization, and Catalysis of H2O2-Based Alkene Epoxidation

Polyoxotungstates [PW(4)O(24)](3-) (PW(4)) and [PW(12)O(40)](3-) (PW(12)) have been inserted into nanocages of the metal organic framework MIL-101. The hybrid materials PW(x)/MIL-101 (x = 4 or 12) containing 5-14 wt % of polyoxotungstate have been obtained and characterized by elemental analysis, N(2) adsorption, FT-IR, Raman, and (31)P NMR MAS spectroscopic techniques. Their catalytic performance was assessed in the selective oxidation of alkenes with aqueous hydrogen peroxide under mild reaction conditions ([H(2)O(2)] = 0.1-0.2 M, 50 degrees C, MeCN). PW(x)/MIL-101 enclosing 5 wt % of polyoxotungstate demonstrated fairly good catalytic activities in the epoxidation of various alkenes (3-carene, limonene, alpha-pinene, cyclohexene, cyclooctene, 1-octene), the turnover frequencies (TOF) and alkene conversions were close to the corresponding parameters achieved with homogeneous PW(x). For the oxidation of substrates with aromatic groups (styrene, cis- and trans-stilbenes), a higher level of olefin conversion was attained using PW(12)/MIL-101. Moreover, confinement of PW(12) within MIL-101 nanocages allowed us to reach higher epoxide selectivities at higher alkene conversions. The hybrid PW(x)/MIL-101 materials were stable to leaching, behaved as true heterogeneous catalysts, were easily recovered by filtration, and reused several times with the maintenance of the catalytic performance.

Mono- and polynuclear aqua complexes and cucurbit[6]uril: Versatile building blocks for supramolecular chemistry

The review surveys new data on the directed construction of supramolecular organic–inorganic compounds from macrocyclic cavitand cucurbit[6]uril (C36H36N24O12)and mono- and polynuclear aqua complexes. Due to the presence of polarized carbonyl groups, cucurbit[6]uril forms strong complexes with alkali, alkaline earth and rare-earth metal ions, and hydrogen-bonded supramolecular adducts with cluster and polynuclear aqua complexes of transitional metals. A wide variety of supramolecular compounds and their unique structures are described.

Cyclohexane selective oxidation over metal–organic frameworks of MIL-101 family: superior catalytic activity and selectivity

Mesoporous metal-organic frameworks Cr- and Fe-MIL-101 are highly efficient, true heterogeneous and recyclable catalysts for solvent-free selective oxidation of cyclohexane with molecular oxygen and/or tert-butyl hydroperoxide under mild conditions.

Sandwich-Type Tetranuclear Lanthanide Complexes with Cucurbit[6]uril: From Molecular Compounds to Coordination Polymers

Sandwich-type lanthanide complexes with macrocyclic ligand cucurbit[6]uril (C 36H 36N 24O 12, CB[6]) were synthesized under hydrothermal conditions from aqueous solutions of lanthanide(III) bromides, CB[6], and 4-cyanopyridine. According to X-ray analysis (Ln = La, Pr, Dy, Ho, Er, and Yb), the compounds with different structural types of lanthanide cores have a common fragment where the tetranuclear hydroxo complex is sandwiched between two macrocycles {(IN@CB[6])Ln 4(mu 3-OH) 4(IN@CB[6])} (6+) (IN = isonicotinate). The photoluminescence (for Ln = Eu) and Fourier transform ion cyclotron resonance mass spectra (for Ln = Pr, Dy, and Er) were studied. The compounds are used for the first time as precursors for the synthesis of lanthanide-silver heterometallic coordination polymers. The chainlike crystal structure of polymers (Ln = La, Pr, and Dy) is constituted by the sandwich complexes linked via the coordination of IN nitrogen atoms to the silver atoms.

Syntheses, Structures, and Electrochemical Properties of Inclusion Compounds of Cucurbit(8)uril with Cobalt(III) and Nickel(II) Complexes

Inclusion compounds of a macrocyclic cavitand cucurbit[8]uril (CB[8]) with cobalt(III) and nickel(II) complexes of 1,3-diaminopropane (tn) and 1,3-diamino-2-propanol (tmOH) { trans-[Co(tn) 2Cl 2]@CB[8]}Cl.14H 2O ( 1), { trans-[Co(tmOH)(tmO)]@CB[8]}Cl 2.22H 2O ( 2), and { trans-[Ni(tmOH) 2]@CB[8]}Cl 2.22H 2O ( 3) were synthesized and characterized by X-ray single crystal analysis, IR spectroscopy, ESI-MS, and by solid-state stripping voltammetry. The encapsulation of trans-[Co(tn) 2Cl 2] (+) within the cavity of CB[8] stabilizes the complex toward ligand substitution reactions in aqueous solution. The electrochemical study demonstrates that CB[8] prefers the oxidized species in trans-[Co(tn) 2Cl 2] (+)/ trans-[Co(tn) 2Cl 2] (0) and trans-[Co(tmO)(tmOH) 2] (2+)/ trans-[Co(tmO)(tmOH) 2] (+) redox couples, but stabilizes the reduced form trans-[Ni(tmOH) 2] (2+) against the oxidized species. The reversibility of voltammogram shapes evidence that for the inclusion compounds 1- 3 electron transfer reactions proceed within the cavity of the host.

Triangular thiocomplexes of molybdenum : reactions with halogens, hydrohalogen acids and phosphines

Abstract The triangular (NH4)2Mo3S13·2H2O complex interacts with Cl2 and Br2 in CH3CN and with concentrated hydrohalogen acids HX (X = Cl, Br and I) retaining its Mo3(μ3-S)(μ-S2)34+ cluster fragment to produce the Mo3(μ3-S)(μ2-S2)3X62− complexes in high yields. IR and Raman spectra of the Mo3S7X62− complexes have been studied. Salts of Mo3S7X62− (X = Cl, Br) containing 92Mo, 100Mo and 34S isotopes and compounds with μ2-(32S-34S) ligands have been also synthesized. For Mo3S7Cl62−, an analysis of the normal vibrations has been performed. The Mo3S7X62− complexes (X = Cl, Br) interact with phosphines (PPh3 and dppe). The reactions proceed with elimination of the μ2-S2 sulfurs to form sulfides of the phosphines and the phosphine complexes Mo3S4X4·3PPh3 and Mo3S4X4·3dppe containing a Mo3S44+ cluster fragment. It has been shown, for the reaction of Mo3(μ3-34S)(μ2-32Se-34Sa)3Cl62− with PPh3, that it is the equatorial μ2-S2 sulfurs that are predominantly eliminated.

Cucurbituril as a New Macrocyclic Ligand for Complexation of Lanthanide Cations in Aqueous Solutions

(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Supramolecular compounds of cucurbituril with molybdenum and tungsten chalcogenide cluster aqua complexes

The review surveys the synthesis and structures of a new class of supramolecular compounds composed of the macrocyclic cavitand cucurbituril and molybdenum or tungsten chalcogenide clusters. The structural motifs of supramolecular compounds and factors influencing their formation are considered.

New Lines of Research in Chemistry of Chalcogenide Complexes: From Clusters to Supramolecular Compounds

The data on the use of the early transition metal chalcogenide clusters as the building units (blocks) in developing the procedures for the target synthesis of the bulky (with nanosizes) complexes, cyanide-bridged polymers of different dimensionality (1D, 2D, and 3D crystal structures), and supramolecular compounds with macrocyclic cavitand cucurbit[6]uryl are considered.

Triangular W3S74+ and W3S44+ complexes

Abstract Methods for the synthesis of triangular thiohalogenide complexes of tungsten W 3 S 7 X 4 (XCl, Br) proceeding from metallic tungsten or WS 3 have been developed. Ways have been found for converting these polymeric complexes to triangular W 3 S 7 X 6 2− complexes which preserve the architecture of the W 3 (μ 3 -S)(μ 2 -S 2 ) 3 4+ cluster fragment. Heating W 3 S 7 X 4 in a PPh 4 X melt or in concentrated acids HX in the presence of Et 4 NX afforded PPh 4+ and Et 4 N + salts of W 3 S 7 X 6 2− (XCl, Br). The structure of (Ph 4 P) 2 W 3 S 7 Br 6 ( III ) was established by X-ray diffraction analysis. The crystals of III are orthorhombic, a =18.082(2), b =25.834(3), c =27.370(2) A, Z =8, Pbca , R ( R w )=0.049 (0.055). The Et 4 N + salt of W 3 34 S 7 Br 6 2− has been obtained and a calculation of the normal vibrations has been performed for W 3 S 7 Br 6 2− . Interaction of W 3 S 7 Br 4 , with a KNCS melt or an aqueous solution of (NH 4 ) 2 S x involves transformation of the cluster fragment W 3 S 7 4+ to a W 3 S 4 4+ fragment to produce W 3 S 4 (NCS) 9 5− and W 3 S 4 (S 4 ) 3 (NH 3 ) 3 2− complexes. The structure of (NH 4 )(H)(H 2 O) 3 W 3 S 16 (NH 3 ) 3 ( VI ) was established by X-ray diffraction analysis. The crystals of VI are trigonal, a =12.508(1), c =10.112(1) A, Z =2, P 31 c , R ( R w )=0.029 (0.033).