Polyoxoanion-Supported Organometallic Complexes: Carbonyls of Rhenium(I), Iridium(I), and Rhodium(I) That Are Soluble Analogs of Solid-Oxide-Supported M(CO)(n)()(+) and That Exhibit Novel M(CO)(n)()(+) Mobility

{Ru(C6 H6 )}-Decorating Heteropolymolybdate for Highly Activity Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde

An unclassical structure of {Ru(C6 H6 )}-based polyoxometalate, Cs6 H4 [Te2 Mo12 O46 {Ru(C6 H6 )}] ⋅ 16.5H2 O (1), has been successfully constructed from {Te2 Mo12 O46 }-type heteropolymolybdate and {Ru(C6 H6 )} group, which structure type was discovered for the first time. Compound 1 not only possesses strong light-harvesting ability, but also exhibits high carrier separation efficiency and lower charge transfer resistance. Under visible light irradiation, compound 1 displayed excellent catalytic activity and circularity in the conversion of benzyl alcohol to benzaldehyde (yield=94 %; turnover number=500; turnover frequency=20.8 h-1 ). Finally, the electron paramagnetic resonance measurement and energy level matching analysis provide theoretical basis for the derivation of the reaction mechanism.

Exploring Wells-Dawson Clusters Associated With the Small Ribosomal Subunit

The polyoxometalate P₂W₁₈O626-, the Wells-Dawson cluster, stabilized the ribosome sufficiently for the crystallographers to solve the phase problem and improve the structural resolution. In the following we characterize the interaction of the Wells-Dawson cluster with the ribosome small subunit. There are 14 different P₂W₁₈O626- clusters interacting with the ribosome, and the types of interactions range from one simple residue interaction to complex association of multiple sites including backbone interactions with a Wells-Dawson cluster. Although well-documented that bridging oxygen atoms are the main basic sites on other polyoxometalate interaction with most proteins reported, the W=O groups are the main sites of the Wells-Dawson cluster interacting with the ribosome. Furthermore, the peptide chain backbone on the ribosome host constitutes the main sites that associate with the Wells-Dawson cluster. In this work we investigate the potential of one representative pair of closely-located Wells-Dawson clusters being a genuine Double Wells-Dawson cluster. We found that the Double Wells-Dawson structure on the ribosome is geometrically sound and in line with other Double Wells-Dawson clusters previously observed in the solid state and solution. This information suggests that the Double Wells-Dawson structure on the ribosome is real and contribute to characterization of this particular structure of the ribosome.

A new phosphotungstate-supported rhenium carbonyl derivative: synthesis, characterization and catalytic selective oxidation of thiophenes

We synthesized a new phosphotungstate-supported rhenium carbonyl derivative, [N(CH₃)₄]₆H₄[P₂W₁₇O₆₂{Re(CO)₃}₂]·25H₂O, existing the first {Re₂} fragment. Moreover, it also exhibits high efficiency for the selective oxidation of thiophenes.

Polyoxometalate-supported metal carbonyl derivatives: from synthetic strategies to structural diversity and applications

This review aims to give an overview of the POM-supported metal carbonyl complexes obtained so far, focusing on their structural diversity and potential photochemical and catalytic properties.

Immobilization of carbonyl rhenium tripods on the surface of a trinickel-substituted Dawson-type polyoxotungstate

A monomeric trinickel(ii)-substituted phosphotungstate [H₉P₂W₁₅O₆₂Ni₃]⁹⁻ ion is stabilized by grafting three {Re(CO)₃} organometallic groups on the surface of a trinickel cluster for the first time. The resulting polyanions [P₂W₁₅O₅₆Ni₃(H₂O)₃(μ₃-OH)₃(Re(CO)₃)₃]⁶⁻ stacked along the a-axis to form a wavy line.

An isotetramolybdate-supported rhenium carbonyl derivative: synthesis, characterization, and use as a catalyst for sulfoxidation

We successfully synthesized an isotetramolybdate-supported rhenium carbonyl derivative, [(CH₃)₄N]₄[{Re(CO)₃}₄(Mo₄O₁₆)]·H₂O, which showed excellent catalytic activity in the selective oxidation of sulfides under comparatively mild reaction conditions.

Isopentatungstate-supported metal carbonyl derivative: synthesis, characterization, and catalytic properties for alkene epoxidation

An isopentatungstate-supported metal carbonyl derivative has been synthesized and characterized, and can efficiently catalyze alkene epoxidation with high activity.

Synthesis and characterization of a series of novel polyoxometalate-supported carbonyl manganese derivatives

A series of novel heteropolytungstates-supported carbonyl manganese derivatives have been synthesized, which are the first examples of grafting [Mn(CO)₃]⁺ moieties and Mn²⁺ on the tungsto-antimonates/bismutates.

Synthesis and Molecular Structure of a Water-Soluble, Dimeric Tri-Titanium(IV)-Substituted Wells-Dawson Polyoxometalate Containing Two Bridging (C5Me5)Rh2+ Groups

A novel trititanium(IV)-substituted Wells-Dawson polyoxometalate (POM)-based organometallic complex, i.e., a dimeric POM containing two bridging Cp*Rh(2+) groups (Cp* = C5Me5) or [{α-P2W15Ti3O60(OH)2}2(Cp*Rh)2](16-) (D-1) with Ci symmetry, was synthesized in an analytically pure form by a 1:2 -molar ratio reaction of the organometallic precursor [Cp*RhCl2]2 with the separately prepared, monomeric trititanium(IV)-substituted Wells-Dawson POM, "[P2W15Ti3O59(OH)3](9-)" (M-1). The crystalline sample (NaK-D-1) of the water-soluble, mixed sodium/potassium salt of D-1 was obtained in the 14.7% yield, which has been characterized by complete elemental analysis, TG/DTA, FTIR, single-crystal X-ray structure analysis, and solution ((183)W, (31)P, (1)H and (13)C{(1)H}) NMR spectroscopy. Single-crystal X-ray structure analysis revealed that the two species of the protonated Wells-Dawson subunits, "[P2W15Ti3O60(OH)2](10-)" were bridged by the two Cp*Rh(2+) groups, resulting in the an overall Ci symmetry. The Cp*Rh(2+) groups were linked to the two terminal oxygen atoms of the titanium(IV) sites and one edge-sharing oxygen atom of the surface Ti-O-Ti bond. The (183)W NMR of D-1 dissolved in D2O showed that its solution structure was represented as a dimeric POM with a formula of [{α-P2W15Ti3O60(OH)3}2{Cp*Rh(OH)}2](16-) (D-2) with Ci (or S2) symmetry. A trititanium(IV)-substituted Wells-Dawson POM-supported organometallic complex has never been reported so far, and thus D-1 in the solid state and D-2 in solution are the first example of this type of complex.

A nona-vacant Keggin-type tricarbonyl rhenium derivative {[PMo3O16][Re(CO)3]4}5− and its catalytic performance for CO2 cycloaddition reactions

A nona-vacant Keggin-type tricarbonyl rhenium derivative {[PMo₃O₁₆][Re(CO)₃]₄}⁵⁻ was synthesized and its frontier orbitals were computed. Interestingly, it showed good catalytic activity for the CO₂ cycloaddition reaction.

Theoretical studies on tricarbonyl metal derivatives of Lindqvist-type polyoxometalate complexes: electronic structures and nonlinear optical properties

The β₀ value of tricarbonyl metal derivatives of a Lindqvist-type polyoxometalate depends on the tricarbonyl metal M. [Nb₂W₄O₁₉Ru(CO)₃]²⁻ has the largest hyperpolarizability, 12.456 × 10⁻³⁰ esu, and might become an excellent NLO material.

Complexation of metal carbonyl units with [α-PW11O39]7− and [α2-P2W17O61]10−: insights into the chiral “twisted-sandwich” dimeric structures

Capturing [M(CO)₃]⁺ (M = Re, Mn) by [α-PW₁₁O₃₉]⁷⁻ or [α₂-P₂W₁₇O₆₁]¹⁰⁻ leads to polyoxometalate-supported metal carbonyl complexes with chiral “twisted-sandwich” structures.

An inorganic chromophore based on a molecular oxide supported metal carbonyl cluster: [P2W17O61{Re(CO)3}3{ORb(H2O)}(μ3-OH)]9-

A polyoxometalate-supported trirhenium carbonyl cluster, mimicking metal oxide supported interfacial dyadic structures, has been synthesized and characterized. Multiple techniques, including computational and transient absorption spectroscopy, have been applied to characterize the charge-transfer dynamics occurring at the interfaces of this "double cluster". The stepwise kinetics of charge separation and recombination has been thoroughly investigated.

Synthesis and characterization of a metal-to-polyoxometalate charge transfer molecular chromophore

[P(4)W(35)O(124){Re(CO)(3)}(2)](16-) (1), a Wells-Dawson [α(2)-P(2)W(17)O(61)](10-) polyoxometalate (POM)-supported [Re(CO)(3)](+) complex containing covalent W(VI)-O-Re(I) bonds has been synthesized and characterized by several methods, including X-ray crystallography. This complex shows a high visible absorptivity (ε(470 nm) = 4000 M(-1) cm(-1) in water) due to the formation of a Re(I)-to-POM charge transfer (MPCT) band. The complex was investigated by computational modeling and transient absorption measurements in the visible and mid-IR regions. Optical excitation of the MPCT transition results in instantaneous (<50 fs) electron transfer from the Re(I) center to the POM ligand.

Ranking the lacunary (Bu4N)9[H[alpha2-P2W17O61]] polyoxometalate's stabilizing ability for Ir(0)(n) nanocluster formation and stabilization using the five-criteria method plus necessary control experiments

The primary goal of the present studies is to rank the monoprotonated, lacunary Wells-Dawson-type polyoxometalate [H[alpha2-P2W17O61]](9-) as a stabilizing anion for the formation and subsequent stabilization of Ir(0)(n) nanoclusters in acetone using the five-criteria method developed previously ( Ozkar , S. ; Finke , R. G. J. Am. Chem. Soc. 2002 , 124, 5796 ). A related goal is to compare this potentially tetradentate, three W-O(-) plus one W-OH ligand [H[alpha2-P2W17O61]](9-) system to the nanocluster formation and stabilization abilities of the present "gold standard" polyoxometalate, [P2W15Nb3O62]9-, with its established tridentate, three Nb-O-Nb ligating system. A comprehensive table of 54 references at present examining polyoxometalates (POMs) as additives/stabilizers of nanoclusters is also provided as Table S1 of the Supporting Information . To accomplish the above-noted two main goals, the organic-solvent-soluble tetrabutylammonium salts, (Bu4N)8.4[H1.6[alpha2-P2W17O61]] x 1.4H2O, (Bu4N)9[H[alpha2-P2W17O61]], and (Bu4N)9[P2W15Nb3O62] were prepared and their basic structures (by IR) and purity (by 31P NMR, plus elemental analysis where appropriate) were determined. The parent Wells-Dawson POM (Bu4N)6[alpha-P2W18O62] was also prepared, characterized, and then used as a control of a polyoxometalate with little surface anionic charge density, one therefore expected to be a poor stabilizer for at least metal(0)(n), overall neutral core, nanoclusters. Also prepared and characterized was (Bu4N)4[H3[PW11O39]], but its attempted deprotonation by (Bu4N)OH with direct 31P NMR monitoring did not yield a clean product by 31P NMR, so studies with this second lacunary POM were deemphasized. The resultant POMs of known composition, protonation state, and thus overall charge were then evaluated by the five criteriathe one presently available methodfor their ability to promote the kinetically controlled formation, stabilization, and subsequent catalytic activity of prototype Ir(0)(n) nanoclusters. A number of additional control experiments necessary to provide confidence in the results are also reported. One main finding is that the efficacy of the POMs studied herein, as stabilizers for Ir(0)(n) nanoclusters in acetone solvent, is [P2W15Nb3O62]9- > [H[alpha2-P2W17O61]]9- >> [alpha-P2W18O62]6- approximately [H3[PW11O39]]4-, the potentially tetradentate, lacunary [H[alpha2-P2W17O61]]9-proving somewhat less efficacious as a stabilizer than the tridentate Nb-O-Nb containing [P2W15Nb3O62]9-POM. Another finding is that the degree of protonation and the overall charge of the POM matter, the more highly charged [H[alpha2-P2W17O61]]9- POM being a better stabilizer then the more protonated, less charged [H2[alpha2-P2W17O61]]8-. Two additional important findings are better insights into the inherent errors underlying three of the five criteria, and thus the use of the five-criteria method itself, and further evidence supporting the hypothesis that future studies of direct measurements of nanocluster agglomeration rate constants k3 and k4 ( Ott , L. S. ; Finke , R. G. Chem. Mater. 2008 , 20, 2592 - 2601 ) should prove valuable.

Synthesis and reactivity of {Ru(p-cymene)}2+derivatives of [Nb6O19]8−: a rational approach towards fluxional organometallic derivatives of polyoxometalates

Three {Ru(p-cym)}(2+) (p-cym = p-cymene) derivatives of [Nb(6)O(19)](8-)-[Nb(6)O(19){Ru(p-cym)}](6-) (Nb(6)Ru(1)), trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) (t-Nb6Ru2), and [Nb(6)O(19){Ru(p-cym)}(4)] (Nb(6)Ru(4))--have been synthesized in water by reaction between [Ru(p-cym)Cl(2)](2) and the hexaniobate. In the solid state, Nb(6)Ru(1) and Nb(6)Ru(4) have been characterized by IR and EDX spectroscopies, whereas t-Nb(6)Ru(2) has been characterized by IR spectroscopy and single-crystal X-ray diffraction (crystal data for K(4)-trans-[Nb(6)O(19){Ru(p-cym)}(2)].14H(2)O (K(4)-t-Nb(6)Ru(2).14H(2)O). In solution, all compounds were characterized by (1)H NMR and ESI mass spectrometry analyses, and Nb(6)Ru(1) was also analyzed by (17)O NMR. These studies allowed a comparison of the differences in behaviour of the three complexes in water: Nb(6)Ru(1) is particularly stable, Nb(6)Ru(4) decomposes by loss of {Ru(p-cym)}(2+) fragments, and trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) isomerizes into cis-[Nb(6)O(19){Ru(p-cym)}(2)](4-). A rational mechanism for the isomerisation of t-Nb(6)Ru(2) is proposed on the basis of a kinetic study.

Synthesis and Characterization of Pt(0) Nanoparticles in Imidazolium Ionic Liquids

The controlled decomposition of Pt2(dba)3 (dba = dibenzylideneacetone) dispersed in 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and hexafluorophosphate (BMI.PF6) ionic liquids in the presence of cyclohexene by molecular hydrogen produces Pt0 nanoparticles. The formation of these nanoparticles follows the two-step [A --> B, A + B --> 2B (k1, k2)] autocatalytic mechanism. The catalytic activity in the hydrogenation of cyclohexene is influenced by the nature of the anion rather than the mean-diameter of the nanoparticles. Thus, higher catalytic activity was obtained with Pt0 dispersed in BMI.BF4 containing the less coordinating anion although these nanoparticles possess a larger mean diameter (3.4 nm) than those obtained in BMI.PF6 (2.3 nm). Similar mean diameter values were estimated from in situ XRD and SAXS. XPS analyses clearly show the interactions of the ionic liquid with the metal surface demonstrating the formation of an ionic liquid protective layer surrounding the platinum nanoparticles. SAXS analysis indicated the formation of a semi-organized ionic liquid layer surrounding the metal particles with an extended molecular length of around 2.8 nm in BMI.BF4 and 3.3 nm in BMI.PF6.

Tunable synthetic approaches for the optimization of nanostructured fuel cell catalysts: An overview

Highly active nanostructured pluri-metal catalysts for fuel cell applications can be obtained by designing synthetic protocol where the particle size, metal composition and morphology can be readily tailored. Tunable synthesis relates to combining the various synthetic methodologies available for generating nanostructured metal catalysts with desired catalytic properties. Herein, we discuss some of these synthetic methodologies which were developed to combine the advantages of each pathway in generating efficient fuel cell catalysts and to learn how the composition and morphology of the metals be fine tuned.

Synthesis and Characterization of the First Carbene Derivative of a Polyoxometalate

Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.

Preparation and characterization of new ruthenium and osmium containing polyoxometalates, [M(DMSO)3Mo7O24](4-) (M = Ru(II), Os(II)), and their use as catalysts for the aerobic oxidation of alcohols

A new heptamolybdate polyoxometalate structure containing ruthenium(II) or osmium(II) metal centers, [M(II)(DMSO)(3)Mo(7)O(24)](4-) (M = Ru, Os), was synthesized by reaction between (NH(4))(6)Mo(7)O(24) and cis-M(DMSO)(4)Cl(2). X-ray structure analysis revealed the complexes to contain a ruthenium/osmium center in a trigonal antiprismatic coordination mode bound to three DMSO moieties via the sulfur atom of DMSO and three oxygen atoms of the new heptamolybdate species. The heptamolybdate consists of seven condensed edge-sharing MoO(6) octahedra with C(2v) symmetry. Three Mo atoms are in classic type II octahedra with a cis dioxo configuration. Two Mo atoms are also type-II-like, but one of the short Mo-O bonds is associated with bridging oxygen atoms rather than terminal oxygen atoms. Two molybdenum atoms are unique in that they are in a trigonally distorted octahedral configuration with three short Mo-O bonds and two intermediate-long M-O bonds and one long Mo-O bond. The [M(II)(DMSO)(3)Mo(7)O(24)](4-) polyoxometalates were effective and in some cases highly selective catalysts for the aerobic oxidation of alcohols to ketones/aldehydes. The integrity of the polyoxometalate was apparently retained at high turnover numbers and throughout the reaction, and a variation of an oxometal type mechanism was proposed to explain the results.

Interplay of cubic building blocks in (et6-arene)ruthenium-containing tungsten and molybdenum oxides

A series of molybdenum and tungsten organometallic oxides containing [Ru(arene)]2+ units (arene =p-cymene, C6Me6) was obtained by condensation of [[Ru(arene)Cl2]2] with oxomolybdates and oxotungstates in aqueous or nonaqueous solvents. The crystal structures of [[Ru(eta6-C6Me6]]4W4O16], [[Ru(eta6-p-MeC6H4iPr]]4W2O10], [[[Ru-(eta6-p-MeC6H4iPr)]2(mu-OH)3]2][[Ru(eta6-p-MeC6H4iPr)]2W8O28(OH)2[Ru(eta6-p-MeC6H4iPr)(H2O)]2], and [[Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) have been determined. While the windmill-type clusters [[Ru(eta6-arene)]4(MO3)4(mu3-O)4] (M = Mo, W; arene =p-MeC6H4iPr, C6Me6), the face-sharing double cubane-type cluster [[Ru(eta6-p-MeC6H4iPr)]4(WO2)2(mu3-O)4(mu4-O)2], and the dimeric cluster [[Ru(eta6-p-MeC6H4iPr)(WO3)3(mu3-O)3(mu3-OH)Ru(eta6-pMeC6H4iPr)(H2O)]2(mu-WO2)2]2- are based on cubane-like units, [(Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) are more properly described as lacunary Lindqvist-type polyoxoanions supporting three ruthenium centers. Precubane clusters [[Ru(eta6-arene)](MO3)2(mu-O)3(mu3-O)]6- are possible intermediates in the formation of these clusters. The cluster structures are retained in solution, except for [[Ru(eta6-p-MeC6H4iPr)]4Mo4O16], which isomerizes to the triple-cubane form.

Robust, Alkali-Stable, Triscarbonyl Metal Derivatives of Hexametalate Anions, [M6O19{M‘(CO)3}n](8-n)- (M = Nb, Ta; M‘ = Mn, Re; n = 1, 2)

Ten 1:1 and 2:1 complexes of [Mn(CO)(3)](+) and [Re(CO)(3)](+) with [Nb(6)O(19)](8)(-) and [Ta(6)O(19)](8)(-) have been isolated as potassium salts in good yields and characterized by elemental analysis, (17)O NMR and infrared spectroscopy, and single-crystal X-ray structure determinations. Crystal data for 1 (t-Re(2)Ta(6)): empirical formula, K(4)Na(2)Re(2)C(6)Ta(6)O(35)H(20), monoclinic, space group, C2/m, a = 17.648(3) A, b = 10.056(1) A, c = 13.171(2) A, beta = 112.531(2) degrees, Z = 2. 2 (t-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(38)H(26), monoclinic, space group, C2/m, a = 17.724(1) A, b = 10.0664(6) A, c = 13.1965(7) A, beta = 112.067(1) degrees, Z = 2. 3 (t-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(37)H(24), monoclinic, space group, C2/m, a = 17.812(2) A, b = 10.098(1) A, c = 13.109(2) A, beta = 112.733(2) degrees, Z = 2. 4 (c-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(50)H(50), triclinic, space group, P1, a = 10.2617(6) A, b = 13.4198(8) A, c = 21.411(1) A, alpha = 72.738(1) degrees, beta = 112.067(1) degrees, gamma = 83.501(1) degrees, Z = 2. 5 (c-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(54)H(58), monoclinic, space group, P2(1)/c, a = 21.687(2) A, b = 10.3085(9) A, c = 26.780(2) A, beta = 108.787(1) degrees, Z = 4. The complexes contain M(CO)(3) groups attached to the surface bridging oxygen atoms of the hexametalate anions to yield structures of nominal C(3)(v)() (1:1), D(3)(d)() (trans 2:1), and C(2)(v)() (cis 2:1) symmetry. The syntheses are carried out in aqueous solution or by aqueous hydrothermal methods, and the complexes have remarkably high thermal, redox, and hydrolytic stabilities. The Re-containing compounds are stable to 400-450 degrees C, at which point CO loss occurs. The Mn compounds lose CO at temperatures above 200 degrees C. Cyclic voltammetry of all complexes in 0.1 M sodium acetate show no redox behavior, except an irreversible oxidation process at approximately 1.0 V vs. Ag/AgCl. In contrast to the parent hexametalate anions that are stable only in alkaline (pH >10) solution, the new complexes are stable, at least kinetically, between pH 4 and pEta approximately 12.