First diastereoselective synthesis of methyl caffeoyl- and feruloyl-muco-quinates.

We report on a diastereoselective synthesis of six derivatives of caffeoyl- and feruloyl-muco-quinic acids. All the muco-quinic acid derivatives were obtained in excellent yield in five steps starting from quinic acid, caffeic acid and ferulic acid. Allyl ether protection of trans-hydroxy cinnamic acids was here introduced to chlorogenic acids synthesis. We show that muco-quinic acid derivatives, which are formally diastereoisomers of chlorogenic acids, can be readily distinguished by their tandem mass spectra.

Trilacunary A-beta-Keggin tungstogermanates and -silicates functionalized with phenyltin(IV) electrophiles.

The first organic derivative of a beta-Keggin tungstogermanate, the monomeric Keggin anion [{(C(6)H(5))Sn(OH)}(3)(A-beta-GeW(9)O(34))](4-) (1), was the only species isolated from the reaction of (C(6)H(5))SnCl(3) with Na(10)[A-beta-GeW(9)O(34)] in water, whereas the Si-analogue [{(C(6)H(5))Sn(OH)}(3)(A-beta-SiW(9)O(34))](4-) (2) and two dimeric tungstosilicates, the unprecedented species [{(C(6)H(5))Sn(A-beta-H(3)SiW(9)Sn(2)O(37))}(2)O(2)](8-) (3) and the known sandwich-type polyanion [{(C(6)H(5))Sn(OH)}(3)(A-beta-H(3)SiW(9)O(34))(2)](8-) (4), were isolated starting from [A-beta-SiW(9)O(34)](10-). The novel polyanion 3 can be described as the product of a double Sn-C hydrolysis followed by condensation of two subunits of 2 through double Sn-O-Sn bridge formation. Solid-state characterization has been carried out by infrared spectroscopy, thermogravimetry and single-crystal X-ray diffraction, representing the first structural analysis for 4. A full solution multinuclear NMR ((1)H, (13)C, (117)Sn, and (183)W) and solid-state (117)Sn CP-MAS NMR study enabled full characterization of 1. A weak 1-dimensional polyanion association through (Sn)O-HO(t) hydrogen contacts involving one of the protonated bridging O atoms of the (C(6)H(5))(3)Sn(3)O(12) corner-shared triad is observed for 1 by X-ray diffraction, resulting in a local C(s) pseudosymmetry for the Sn centers detected by solid-state (117)Sn NMR spectroscopy.

Organo-ruthenium supported heteropolytungstates: synthesis, structure, electrochemistry, and oxidation catalysis.

The reaction of [Ru(arene)Cl(2)](2) (arene = benzene, p-cymene) with [X(2)W(22)O(74)(OH)(2)](12-) (X = Sb(III), Bi(III)) in buffer medium resulted in four organo-ruthenium supported heteropolytungstates, [Sb(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (1), [Bi(2)W(20)O(70)(RuC(6)H(6))(2)](10-) (2), [Sb(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (3), and [Bi(2)W(20)O(70)(RuC(10)H(14))(2)](10-) (4), which have been characterized in solution by multinuclear ((183)W, (13)C, (1)H) NMR, UV-vis spectroscopy, electrochemistry, and in the solid state by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Polyanions 1, 2, and 4 crystallize in the triclinic system, space group P1 with the following unit cell parameters: K(5)Na(5)[Sb(2)W(20)O(70)(RuC(6)H(6))(2)] x 22 H(2)O (KNa-1), a = 12.1625(2) A, b = 13.1677(2) A, c = 16.0141(3) A, alpha = 78.9201(7) degrees, beta = 74.4442(8) degrees, gamma = 78.9019(8) degrees, and Z = 1; Cs(2)Na(8)[Bi(2)W(20)O(70)(RuC(6)H(6))(2)] x 30 H(2)O (CsNa-2), a = 11.6353(7) A, b = 13.3638(7) A, c = 16.7067(8) A, alpha = 79.568(2) degrees, beta = 71.103(2) degrees, gamma = 80.331(2) degrees, and Z = 1; Na(10)[Bi(2)W(20)O(70)(RuC(10)H(14))(2)].35H(2)O (Na-4), a = 15.7376(12) A, b = 15.9806(13) A, c = 24.2909(19) A, alpha = 92.109(4) degrees, beta = 101.354(4) degrees, gamma = 97.365(3) degrees, and Z = 2. Polyanions 1-4 consist of two (L)Ru(2+) (L = benzene or p-cymene) units linked to a [X(2)W(20)O(70)](14-) (X = Sb(III), Bi(III)) fragment via Ru-O(W) bonds resulting in an assembly with idealized C(2h) symmetry. Polyanions 1-4 are stable in solution as indicated by the expected (183)W, (13)C, and (1)H NMR spectra. The electrochemistry of 1-4 is described by considering the reduction and the oxidation processes. The nature of the arene in Ru(arene) has practically no influence on the formal potentials of the W-centers, which are more sensitive to the Sb or Bi hetero atoms. The results suggest that the respective Sb- and Bi derivatives have very different pK(a) values, with the reduced form of 1 being the most basic, thus permitting the observation of two well-developed voltammetric waves at pH 6. In contrast, the identity of the arene influences the oxidation processes, thus permitting to distinguish them. A strong electrocatalytic water oxidation peak is observed that is more positive than the one corresponding to the Ru(arene) oxidation process. Also a stepwise oxidation of the Ru(benzene) group could be observed at pH 3. The catalytic efficiency, on the other hand, of 1-4 toward the oxidation of n-hexadecane and p-xylene illustrated the effect of ruthenium substitution on the polyanion catalytic performance.

Heteropoly-13-palladates(II) [Pd(II)(13)(As(V)Ph)(8)O(32)](6-) and [Pd(II)(13)Se(IV)(8)O(32)](6-).

Two discrete anionic palladium(II)-oxo clusters have been prepared: [Pd(13)(As(V)Ph)(8)O(32)](6-) (1) and [Pd(13)Se(IV)(8)O(32)](6-) (2) were synthesized in one-pot self-assembly reactions of Pd(OAc)(2) with PhAsO(3)H(2) and SeO(2) and characterized by single-crystal X-ray analysis, IR, thermogravimetric analysis, elemental analysis, magnetic and electron paramagnetic resonance measurements, and electrochemistry.

Copper-, cobalt-, and manganese-containing 17-tungsto-2-germanates.

The sandwich-type tungstogermanates [Cu(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))](12-) (1), [Co(H(2)O)(2){Co(3)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (2), and [Mn(H(2)O)(2){Mn(3)(H(2)O)(B-beta-GeW(9)O(33)(OH))(B-beta-GeW(8)O(30)(OH))}(2)](22-) (3) were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, and infrared spectroscopy. Polyanion 1 is composed of two nonequivalent Keggin units, (B-beta-GeW(8)O(31)) and (B-beta-GeW(9)O(34)), linked to each other via three copper(II) ions in such a way that there is a plane of symmetry passing through both Ge atoms and the unique Cu atom, resulting in a sandwich-type structure with C(s) symmetry. On the other hand, the monomeric building blocks of 2 and 3 contain the same Keggin fragments as 1, but linked through three octahedrally coordinated Co(2+) or Mn(2+) ions. The major difference between complex 1 and complexes 2 and 3 is that the latter all lack a plane of symmetry due to a different orientation of the rotated triad. Magnetic measurements indicated antiferromagnetic exchange interactions between the three Cu(2+) ions in 1 and between the three Mn(2+) ions in 3. On the other hand, polyanion 2 possesses ferromagnetic interaction of the Co(2+) ions. The best least-squares fit values for 2 are J(z) = 7.9 cm(-1), J(z) = 3.1 cm(-1), J(y) = 2.4 cm(-1), g(z) = 6.77 cm(-1), and g(xy) = 4.15 (R = 2.6 x 10(-2)).

22-Isopolytungstate fragment [H2W22O74]14- coordinated to lanthanide ions.

The novel polyanions [Ln(2)(H(2)O)(10)W(22)O(71)(OH)(2)](8-) (Ln = La (1), Ce (2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), Yb (8), Lu (9), Y (10)) have been synthesized by reaction of WO(4)(2-) and lanthanide ions in acidic aqueous medium. The low symmetry (C(i)) polyanion family [Ln(2)(H(2)O)(10)W(22)O(71)(OH)(2)](8-) consists of the isopolyanion [H(2)W(22)O(74)](14-) and two {Ln(H(2)O)(5)}(3+) supporting units. The [H(2)W(22)O(74)](14-) cluster, which consists of two undecatungstate {W(11)} fragments, acts as a tridentate ligand to two Ln(3+) ions. Polyanions 1-10 are isostructural, and the coordination number of the lanthanide ions correlates with their sizes. All compounds have been fully characterized in the solid state by Fourier transform infrared spectroscopy, single-crystal X-ray diffraction, thermogravimetric analysis, and elemental analysis. Single-crystal X-ray diffraction analyses show that 1-10 crystallize as sodium salts in the triclinic space group P1.

Large cation-anion materials based on trinuclear ruthenium(III) salts of Keggin and Wells-Dawson anions having water-filled channels.

Reaction of the trinuclear ruthenium(III) cation [Ru(3)O(OOCCH(3))(6)(CH(3)OH)(3)](+) with the Keggin-type [alpha-GeW(11)O(39)](8-), [alpha-SiW(11)O(39)](8-), and [alpha-SiMo(12)O(40)](4-) and the Wells-Dawson-type [alpha-P(2)W(18)O(62)](6-) polyanions in an aqueous, acidic medium resulted in plenary polyoxometalate-based materials K(2)Na[Ru(3)O(OOCCH(3))(6)(H(2)O)(3)][alpha-GeW(12)O(40)].10H(2)O (1), K(3)[Ru(3)O(OOCCH(3))(6)(H(2)O)(3)][alpha-SiW(12)O(40)].18H(2)O (2), K(3)[Ru(3)O(OOCCH(3))(6)(H(2)O)(3)][alpha-SiMo(12)O(40)].7H(2)O (3), and K(2)Na[Ru(3)O(OOCCH(3))(6)(H(2)O)(3)](3)[alpha-P(2)W(18)O(62)].26H(2)O (4), respectively. All four materials, 1-4, crystallize as sodium and/or potassium salts in the monoclinic space group P2(1)/n. Compounds 1-4 were characterized by IR, thermogravimetric analysis, and single-crystal/powder X-ray diffraction (XRD). The isolated solid-state frameworks, composed of cocrystallized trinuclear ruthenium cations and polyanions, exhibit nanosized voids filled with crystal waters. These water molecules can be removed reversibly upon heating under a vacuum, and powder XRD measurements demonstrated that the crystallinity of the compound was preserved. Sorption studies on ethanol and methanol were also performed.

Organoantimony-containing polyoxometalate: [{PhSbOH}3(A-alpha-PW9O34)2]9-.

The dimeric, sandwich-type tungstophosphate [{PhSbOH}(3)(A-alpha-PW(9)O(34))(2)](9-) (1) has idealized D(3h) symmetry and represents the first organoantimony-containing polyoxometalate. Polyanion 1 was synthesized in an aqueous, acidic medium via three different routes and was fully characterized in the solid state by X-ray diffraction, IR, and thermogravimetric analysis and in solution by multinuclear NMR ((1)H, (13)C, (31)P, and (183)W).

The first 3-dimensional assemblies of organotin-functionalized polyanions.

Reaction of the (CH(3))(2)Sn(2+) electrophile toward trilacunary [A-alpha-XW(9)O(34)](n-) Keggin polytungstates (X = P(V), As(V), Si(IV)) with guanidinium as templating-cation resulted in the isostructural compounds Na[C(NH(2))(3)](2)[{(CH(3))(2)Sn(H(2)O)}(3)(A-alpha-PW(9)O(34))] x 9 H(2)O (1), Na[C(NH(2))(3)](2)[{(CH(3))(2)Sn(H(2)O)}(3)(A-alpha-AsW(9)O(34))] x 8 H(2)O (2) and Na(2)[C(NH(2))(3)](2)[{(CH(3))(2)Sn(H(2)O)}(3)(A-alpha-SiW(9)O(34))] x 10 H(2)O (3). Compounds 1-3 constitute the first 3-dimensional assemblies of organotin-functionalized polyanions, as well as the first example of a dimethyltin-containing tungstosilicate in the case of 3, and they show a similar chiral architecture based on tetrahedrally-arranged {(CH(3))(2)Sn}(3)(A-alpha-XW(9)O(34)) monomeric building-blocks connected via intermolecular Sn-O=W bridges regardless of the size and/or charge of the heteroatom.

Cyclic Ti9 keggin trimers with tetrahedral (PO4) or octahedral (TiO6) capping groups.

We have synthesized the cyclic Ti 9 Keggin trimers [(alpha-Ti 3PW 9O 38) 3(PO 4)] (18-) ( 1) and [(alpha-Ti 3SiW 9O 37OH) 3(TiO 3(OH 2) 3)] (17-) ( 2), which are both composed of three (Ti 3XW 9O 37) units (X = P or Si) linked via three Ti-O-Ti bridges and a capping group, which is either tetrahedral PO 4 ( 1) or octahedral TiO 6 ( 2). Polyanions 1 and 2 were fully characterized in the solid state (IR, X-ray diffraction, thermogravimetric and elemental analyses) and in solution ( (31)P or (183)W NMR).

Phenyltin-substituted 9-tungstogermanate and comparison with its tungstosilicate analogue.

Reaction of (C 6H 5)SnCl 3 with Na 10[ A-alpha-GeW 9O 34] in water results in the monomeric, trisubstituted Keggin species [{(C 6H 5)Sn(OH)} 3( A-alpha-GeW 9O 34)] (4-) ( 1), constituting the first organotin derivative of a trilacunary Keggin tungstogermanate. Polyanion 1 could be obtained as two different cesium salts depending on the applied isolation strategy: Cs 3Na[{(C 6H 5)Sn(OH)} 3( A-alpha-GeW 9O 34)].9H 2O ( CsNa-1) and Cs 3[{(C 6H 5)Sn(OH)} 3( A-alpha-HGeW 9O 34)].8H 2O ( Cs-H1). The monomeric phenyltin-containing tungstosilicate [{(C 6H 5)Sn(OH)} 3( A-alpha-SiW 9O 34)] (4-) ( 2) and the dimeric, sandwich-type derivative [{(C 6H 5)Sn(OH)} 3( A-alpha-H 3SiW 9O 34) 2] (8-) ( 3) have also been isolated as the cesium salts Cs 3Na[{(C 6H 5)Sn(OH)} 3( A-alpha-SiW 9O 34)].9H 2O ( CsNa-2), Cs 4[{(C 6H 5)Sn(OH)} 3( A-alpha-SiW 9O 34)].13H 2O ( Cs-2), and Cs 8[{(C 6H 5)Sn(OH)} 3( A-alpha-H 3SiW 9O 34) 2].23H 2O ( Cs-3), respectively. We have investigated in detail the similarities and differences in the reactivity of (C 6H 5)Sn (3+) with [ A-alpha-GeW 9O 34] (10-) vs [ A-alpha-SiW 9O 34] (10-). All five compounds have been characterized in the solid state by means of elemental analysis, infrared spectroscopy, thermogravimetry, and single-crystal X-ray diffraction, representing the first structural analysis for polyanions 1- 3. A full solution characterization of 1 by multinuclear NMR spectroscopy ( (1)H, (13)C, (119)Sn, and (183)W) has also been performed. The monomeric polyanions 1 and 2 are closely associated in the solid state through (Sn)O-H...O t (O t: terminal oxygen atom) hydrogen bonds reinforced by weak C-H...O t contacts to form 2-dimensional ( CsNa-1 and CsNa-2) or 1-dimensional ( Cs-H1) arrangements, and also dimeric entities ( Cs-2) depending on the network of intermolecular interactions.

6-Peroxo-6-zirconium crown and its hafnium analogue embedded in a triangular polyanion: [M6(O2)6(OH)6(gamma-SiW10O36)3]18- (M = Zr, Hf).

We have synthesized and structurally characterized the unprecedented peroxo-zirconium(IV) containing [Zr6(O2)6(OH)6(gamma-SiW10O36)3]18- (1). Polyanion 1 comprises a cyclic 6-peroxo-6-zirconium core stabilized by three decatungstosilicate units. We have also prepared the isostructural hafnium(IV) analogue [Hf6(O2)6(OH)6(gamma-SiW10O36)3]18- (2). We investigated the acid/base and redox properties of 1 by UV-vis spectroscopy and electrochemistry studies. Polyanion 1 represents the first structurally characterized Zr-peroxo POM with side-on, bridging peroxo units. The simple, one-pot synthesis of 1 and 2 involving dropwise addition of aqueous hydrogen peroxide could represent a general procedure for incorporating peroxo groups into a large variety of transition metal and lanthanide containing POMs.

Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in a 16-metal-centre iron oxide nanocluster.

The 16-Fe(III)-containing 48-tungsto-8-phosphate [P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)](20-) (1) has been synthesised and characterised by IR and ESR spectroscopy, TGA, elemental analyses, electrochemistry and susceptibility measurements. Single-crystal X-ray analyses were carried out on Li(4)K(16)[P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)]66 H(2)O2 KCl (LiK-1, orthorhombic space group Pnnm, a=36.3777(9) A, b=13.9708(3) A, c=26.9140(7) A, and Z=2) and on the corresponding mixed sodium-potassium salt Na(9)K(11)[P(8)W(48)O(184)Fe(16)(OH)(28)(H(2)O)(4)].100 H(2)O (NaK-1, monoclinic space group C2/c, a=46.552(4) A, b=20.8239(18) A, c=27.826(2) A, beta=97.141(2) degrees and Z=4). Polyanion 1 contains--in the form of a cyclic arrangement--the unprecedented {Fe(16)(OH)(28)(H(2)O)(4)}(20+) nanocluster, with 16 edge- and corner-sharing FeO(6) octahedra, grafted on the inner surface of the crown-shaped [H(7)P(8)W(48)O(184)](33-) (P(8)W(48)) precursor. The synthesis of 1 was accomplished by reaction of different iron species containing Fe(II) (in presence of O(2)) or Fe(III) ions with the P(8)W(48) anion in aqueous, acidic medium (pH approximately 4), which can be regarded as an assembly process under confined geometries. One fascinating aspect is the possibility to model the uptake and release of iron in ferritin. The electrochemical study of 1, which is stable from pH 1 through 7, offers an interesting example of a highly iron-rich cluster. The reduction wave associated with the Fe(III) centres could not be split in distinct steps independent of the potential scan rate from 2 to 1000 mV s(-1); this is in full agreement with the structure showing that all 16 iron centres are equivalent. Polyanion 1 proved to be efficient for the electrocatalytic reduction of NO(x), including nitrate. Magnetic and variable frequency EPR measurements on 1 suggest that the Fe(III) ions are strongly antiferromagnetically coupled and that the ground state is tentatively spin S=2.

Carbonyl-ruthenium substituted alpha-Keggin-tungstosilicate, [alpha-SiW(11)O(39)Ru(II)(CO)](6-): synthesis, structure, redox studies and reactivity.

The carbonyl-ruthenium substituted undecatungstosilicate [alpha-SiW(11)O(39)Ru(II)(CO)](6-) () was isolated as a caesium salt and successfully characterized by using (183)W and (13)C NMR, elemental analysis, IR, UV-vis and cyclic voltammetry (CV). Polyanion represents the first example of a metal-carbonyl moiety being fully incorporated into the polyoxometalate (POM). As a result, the Ru(CO) moiety became redox active and was reversibly oxidized to the one-electron ruthenium(iii) derivative, [alpha-SiW(11)O(39)Ru(III)(CO)](5-). This Ru(III)(CO) moiety was unexpectedly stable in aqueous solution compared to the organo-ruthenium carbonyl derivatives and could be detected by using UV-vis and in situ IR coupled with electrolysis. The oxidized ruthenium(iii) derivative slowly released CO in aqueous solution, resulting in the aqua species [alpha-SiW(11)O(39)Ru(III)(H(2)O)](5-) and then the dimeric POM species by condensation. Furthermore, could be converted to the corresponding aqua polyanion by photo-irradiation.

Low-temperature phase of hexaguanidinium hepta-molybdate monohydrate.

The crystal structure of the title compound, [C(NH(2))(3)](6)[Mo(7)O(24)]·H(2)O, previously determined at room temperature in the monoclinic space group C2/c from Weissenberg techniques [Don & Weakley (1981 ▶). Acta Cryst. B37, 451-453], has been redetermined from low-temperature single-crystal data in the monoclinic space group P2(1)/c. The asymmetric unit contains one hepta-molybdate anion, six guanidinium cations and one water mol-ecule of hydration. The anions and cations are linked by an extensive network of N-H⋯O hydrogen bonds.