Abstract  Concise synthesis of the glycone part (a pentasaccharide) of the anti-leishmanial triterpenoid saponin isolated from Maesa balansae is reported. A late-stage TEMPO-mediated oxidation of a primary hydroxyl group to carboxylic acid has been achieved under phase-transfer conditions. Glycosylations were performed either by thioglycoside or glycosyl trichloroacetimidate activation using sulfuric acid immobilized on silica (H2SO4-silica) in conjunction with N-iodosuccinimide and alone, respectively. H2SO4-silica was proved to be a better choice as promoter than conventional Lewis acid promoters such as TfOH or TMSOTf

Abstract  The synthesis of either anomers of aryl 2-deoxy-d-glycopyranosides from 2-deoxy-1-thioglycosides is reported. The [alpha]-anomers form as the major product when thioglycosides react with differently substituted phenols and naphthols, in the presence of N-iodosuccinimide/triflic acid. On the other hand, reaction of the thioglycosides with bromine initially, followed by reaction with aryloxy anions lead to aryl 2-deoxy-[beta]-d-glycosides with high specificities.

Abstract  Complex OsH{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2 (1) reacts with 1 equiv of trifluoromethanesulfonic acid (HOTf) and trifluoromethanesulfonic acid-d1 (DOTf) to produce the dihydride and hydride-deuteride complexes, [OsHE{eta5-C5H4(CH2)2NMe2}(P(i)Pr3)2]OTf (E = H (2), D (2-d1), respectively. Treatment of 2 and 2-d1 with a second equivalent of HOTf gives [OsHE{eta5-C5H4(CH2)2NHMe2}(P(i)Pr3)2][OTf]2 (E = H (3), D (3-d1) as a result of the protonation of the nitrogen atom. While the hydride and deuteride ligands of 2, 2-d1, 3, and 3-d1 do not undergo any H/D exchange process with the solvent, in acetone-d6, the NH proton of 3 and 3-d1 changes places with a deuterium atom of the solvent to yield [OsHE{eta5-C5H4(CH2)2NDMe2}(P(i)Pr3)2][OTf]2 (E = H (3-Nd1), D (3-d2)). Complex 3-Nd1 can also be obtained from the treatment of complex 2 with DOTf in dichloromethane. No exchange process between the hydride and the ND positions in 3-Nd1 or between the deuteride and NH positions in 3-d1 has been observed. Treatment of 3-Nd1 and 3-d1 with sodium methoxide results in a selective reaction of the base with the ammonium group to regenerate 2 and 2-d1, respectively. Complex 1 also reacts with methyl and methyl-d3 trifluoromethanesulfonate (CH3OTf and CD3OTf, respectively) to give [OsH{eta5-C5H4(CH2)2NMe2CE3}(P(i)Pr3)2]OTf (E = H (4), D (4-d3)) as a result of the addition of the CE3 (E = H, D) group to the nitrogen atom. Complex 4 has been characterized by an X-ray diffraction analysis. It reacts with a second molecule of CH3OTf or CD3OTf to produce [OsH{eta5-C5H4(CH2)2NMe3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5). Similarly, complex 4-d3 reacts with a second molecule of CH3OTf or CD3OTf to yield [OsH{eta5-C5H4(CH2)2NMe2CD3}{CH2CH(CH3)P(i)P2}(P(i)Pr3)[OTf]2 (5-d3). In acetonitrile, complex 5 evolves to an equilibrium mixture of the acetonitrile adducts [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)(P(i)Pr3)2][OTf]2 (7) and [Os{eta5-C5H4(CH2)2NMe3}(NCCH3)2(P(i)Pr3)][OTf]2 (8). In methanol or methanol-d4, complex 4 is not stable and loses trimethylamine to give the vinylcyclopentadienyl derivatives [OsHE(eta5-C5H4CH=CH2)(P(i)Pr3)2]OTf (E = H (9), D (9-d1)) as a result of the protonation or deuteration of the metallic center and a subsequent Hofmann elimination. Protonation of 4 with HOTf gives the dihydride-trimethylammonium derivative [OsH2{eta5-C5H4(CH2)2NMe3}(P(i)Pr3)2][OTf]2 (10). Treatment of 9 with sodium methoxide produces OsH(eta5-C5H4CH=CH2)(P(i)Pr3)2 (11).

Abstract  A highly efficient silver triflate and N-heterocyclic carbene co-catalyzed three-component reaction of N'-(2-alkynylbenzylidene)hydrazide, methanol with alpha,beta-unsaturated aldehyde is described, which gives rise to the 2-amino-1,2-dihydroisoquinolines in good yield.

Abstract  Pd(II) complexes in which 2-pyridyldiphenylphosphine (Ph(2)Ppy) chelates the Pd(II) centre have been prepared and characterized by multinuclear NMR spectroscopy and by X-ray crystallographic analysis. trans-[Pd(kappa(1)-Ph(2)Ppy)(2)Cl(2)] is transformed into [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)Cl]Cl by the addition of a few drops of methanol to dichloromethane solutions, and into [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)Cl]X by addition of AgX or TlX, (X = BF(4)(-), CF(3)SO(3)(-) or MeSO(3)(-)). [Pd(kappa(1)-Ph(2)Ppy)(2)(p-benzoquinone)] can be transformed into [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)(MeSO(3))][MeSO(3)] by the addition of two equivalents of MeSO(3)H. Addition of further MeSO(3)H affords [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)PpyH)(MeSO(3))][MeSO(3)](2). Addition of two equivalents of CF(3)SO(3)H, MeSO(3)H or CF(3)CO(2)H and two equivalents of Ph(2)Ppy to [Pd(OAc)(2)] in CH(2)Cl(2) or CH(2)Cl(2)-MeOH affords [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)X]X, (X = CF(3)SO(3)(-), MeSO(3)(-) or CF(3)CO(2)(-)), however addition of two equivalents of HBF(4).Et(2)O affords a different complex, tentatively formulated as [Pd(kappa(2)-Ph(2)Ppy)(2)]X(2). Addition of excess acid results in the clean formation of [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)PpyH)(X)]X(2). In methanol, addition of MeSO(3)H and three equivalents of Ph(2)Ppy to [Pd(OAc)(2)] affords [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)(2)][MeSO(3)](2) as the principal Pd-phosphine complex. The fluxional processes occuring in these complexes and in [Pd (kappa(1)-Ph(2)Ppy)(3)Cl]X, (X = Cl, OTf) and the potential for hemilability of the Ph(2)Ppy ligand has been investigated by variable-temperature NMR. The activation entropy and enthalpy for the regiospecific fluxional processes occuring in [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)(2)][MeSO(3)](2) have been determined and are in the range -10 to -30 J mol(-1) K(-1) and ca. 30 kJ mol(-1) respectively, consistent with associative pathways being followed. The observed regioselectivities of the exchanges are attributed to the constraints imposed by microscopic reversibility and the small bite angle of the Ph(2)Ppy ligand. X-Ray crystal structure determinations of trans-[Pd(kappa(1)-Ph(2)Ppy)(2)Cl(2)], [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)Cl][BF(4)], [Pd(kappa(1)-Ph(2)Ppy)(2)(p-benzoquinone)], trans-[Pd(kappa(1)-Ph(2)PpyH)(2)Cl(2)][MeSO(3)](2), and [Pd(kappa(1)-Ph(2)Ppy)(3)Cl](Cl) are reported. In [Pd(kappa(2)-Ph(2)Ppy)(kappa(1)-Ph(2)Ppy)Cl][BF(4)] a donor-acceptor interaction is seen between the pyridyl-N of the monodentate Ph(2)Ppy ligand and the phosphorus of the chelating Ph(2)Ppy resulting in a trigonal bipyramidal geometry at this phosphorus.

Abstract  [trans-Fe(H(2))(CO)(dppe)(2)](2+) (3) (dppe = 1,2-bis(diphenylphosphino)ethane) was generated by protonation of [trans-FeH(CO)(dppe)(2)](+) in CD(2)Cl(2). [trans-Fe(H(2))(CO)(depe)(2)](2+) (6) (depe = 1,2-bis(diethylphosphino)ethane) was generated by the treatment of [trans-FeCl(CO)(depe)(2)](+) in CD(2)Cl(2) with AgSbF(6) under 1 atm of H(2). Complex 3 is more acidic than trifluoromethanesulfonic acid (HOTf) in CD(2)Cl(2), while 6 is suspected to be less acidic than [Et(2)OH](+). 3[OTf](2) is stable to H(2) loss under reduced pressure for several hours, an indication of strong three-center (Fe-H(2)), two-electron sigma-bonding. Both complexes 3 and 6 undergo H(2) substitution reactions. There is evidence of the formation of [trans-Fe(H(2)O)(CO)(dppe)(2)](2+) and [trans-Fe(OTf)(CO)(dppe)(2)](+), although these complexes could not be isolated. [trans-FeY(CO)(depe)(2)]Y complexes (Y(-) = [BF(4)](-), 7[BF(4)]; Y(-) = [OTf](-), 8[OTf]) were isolated from the corresponding reactions of [trans-FeH(CO)(depe)(2)]Y with [Et(2)OH][BF(4)] or HOTf. 7[BF(4)] was structurally characterized by single-crystal X-ray diffraction. Attempts to grow crystals of 8[OTf] yielded salts containing the complex [trans-Fe(H(2)O)(CO)(depe)(2)](2+) (9), which were structurally characterized by single-crystal X-ray diffraction. Coordination of [BF(4)](-) in 7[BF(4)] was demonstrated, by variable-temperature (31)P{(1)H} NMR spectroscopy, to be dynamic. Dissolving 7[BF(4)] in methanol results in nucleophilic substitution at B to yield the new complex [trans-FeF(CO)(depe)(2)](+) (10). An attempt to grow crystals of 10[BF(4)] from the reaction mixture resulted in crystals of [H(2)(depe)][BF(4)], which were structurally characterized by single-crystal X-ray diffraction.

Abstract  We recently reported on a high-power nanoporous proton-conducting membrane (NP-PCM)-based direct methanol fuel cell (DMFC) operated with triflic acid. However, accompanying the advantages of methanol as a fuel, such as low cost and ease of handling and storage, are several pronounced disadvantages: toxicity, high flammability, low boiling point (65 degrees C) and the strong tendency to pass through the polymer-exchange membrane (high crossover). The focus of this work is the development of a high-power direct ethylene glycol fuel cell (DEGFC) based on the NP-PCM. Ethylene glycol (EG) has a theoretical capacity 17% higher than that of methanol in terms of Ah ml(-1) (4.8 and 4, respectively); this is especially important for portable electronic devices. It is also a safer (bp 198 degrees C) fuel for direct-oxidation fuel cell (DOFC) applications. Maximum power densities of 320 mW cm(-2) (at 0.32 V) at 130 degrees C have been achieved in the DEGFC fed with 0.72 M ethylene glycol in 1.7 M triflic acid at 3 atm at the anode and with dry air at 3.7 atm at the cathode. The cell platinum loading was 4 Mg pt cm(-2) on each electrode. The overpotentials at the cathodes and at the anodes of the DEGFC and DMFC were measured, compared and discussed. (c) 2006 Elsevier B.V. All rights reserved.

Abstract  In the aqueous chemistry of molybdenum(IV) and tungsten(IV), trinuclear, incomplete cubane-like, oxo and sulfido clusters of the type [M3E4]4+ (M = Mo, W; E = O, S) play a central role. We here describe how formato complexes of all these cluster cores can be prepared in high yields by crystallization from methanol-water or ethanol-water mixtures. Since potassium and ammonium formate are very soluble in these alcohol-water mixtures, high formate concentrations could be accomplished in the solutions from which the corresponding salts of cluster formato complexes crystallized. The [Mo3O4]4+ compounds could be synthesized without requiring the use of noncomplexing acids in the process. Some [M3E4]4+ compounds were characterized by single-crystal structure determinations. [NH4]3.20[K]0.80[H3O][Mo3O4(HCO2)8][HCO2].H2O was triclinic, space group P1 (No. 2) with a = 11.011(2) A, b = 13.310(2) A, c = 9.993(1) A, alpha = 106.817(7) degrees, beta = 91.651(9) degrees, gamma = 88.340(9) degrees, and two formula units per cell. [K]6[W3S4(HCO2)9][HCO2].2.27H2O.0.73CH3OH was monoclinic, space group C2/m (No. 12) with a = 19.605(6) A, b = 14.458(7) A, c = 13.627(5) A, beta = 118.94(2) degrees, and four formula units per cell. Generally, the nine coordination sites of [M3E4]4+ were occupied either by a mixture of monodentate and mu 2-bridging formato ligands or by monodentate formato ligands only. By dissolution in noncomplexing strong acid, all the formato complexes immediately hydrolyzed to form [M3E4(H2O)9]4+ aqua complexes. This allows, for example, high concentrations of [Mo3S4(H2O)9]4+ in CF3SO3H to be obtained and these solutions to be used for the synthesis of bimetallic clusters containing the cubane-like motif Mo3M'S4.

Abstract  In water, the antineoplastic drug cisplatin, cis-[PtCl2(NH3)2] (1) hydrolyses slowly to the aqua complexes cis-[Pt(NH3)2Cl(H2O)]+ (2) and, to a small extent, cis-[Pt(NH3)2(H2O)2]2+ (3), which are thought to play an important role in the metabolism of cisplatin. HPLC is a useful technique for monitoring 2 and 3, but only if the components of the mobile phase used in the reverse phase HPLC technique are unreactive toward these aqua complexes under the conditions of the experiment. 15N Nuclear magnetic resonance (NMR) with samples highly enriched (>98%) in 15N has been used to check the reactivity of 2 and 3 toward substances commonly used as components of the mobile phase. The results reported herein indicate that acetonitrile, often used as an organic modifier, reacts readily with 2 and 3. Methanol, also commonly employed, is much less reactive. Carboxylic acids RCO2H (R = CH3, H, CF3), which are frequently used to adjust pH of the mobile phase, also react readily with 2 and 3. Trifluoromethanesulfonic acid ("triflic acid"), CF3SO3H, is unreactive. Neither hexanesulfonic acid nor sodium dodecyl sulfate (SDS), used as "ion-pairing agents", reacts significantly with 2 or 3 under the experimental conditions, but SDS gives better peak separation. Commercial SDS must, however, be purified from chloride contamination. From our studies, optimal conditions for HPLC separation of 1, 2, and 3, with a C18 stationary phase at 37 degrees C, require an aqueous mobile phase with 3% v/v methanol, 0.05 mM SDS, and pH 2.5 (adjusted with triflic acid). This technique was then used to measure levels of 1, 2, and 3 in ultrafiltered serum after incubation for various times with cisplatin at 37 degrees C.

Abstract  Although cations with three heteroatoms, such as monoprotonated guanidine and urea, are stabilized by Y-shaped conjugation and such Y-conjugated cations are sufficiently basic to be further protonated (or protosolvated) to dications in strongly acid media, only O-monoprotonated species have been detected in the case of carbamates even in magic acid. We found that the trifluoromethanesulfonic acid catalyzed cyclization of arylethylcarbamates proceeds to afford dihydroisoquinolones in high yield. In strong acids, methyl carbamates are fully O-monoprotonated, and these monocations do not undergo cyclization even under heating. But, as the acidity of the reaction medium is further increased, the cyclization reaction of methyl phenethylcarbamates starts to proceed as a first-order reaction, with a linear relationship between rate and acidity. The sign and magnitude of the entropy of activation Delta S-double dagger were found to be similar to those of other A(Ac)1 reactions. These results strongly support the idea that further protonation of the O-protonated carbamates is involved in the cyclization, but the Concentration of the dications is very low and suggests that the rate determining step is dissociation of methanol from the diprotonated Carbamate to generate protonated isocyanate, which reacts with the aromatic ring. Therefore, O-protonated carbamates are weak bases in sharp contrast to other Y-shaped monocations.

Abstract  In extension of recent synthetic and crystallographic studies of adducts of silver(I) oxyanion salts with uni- and bi-dentate nitrogen-donor ligands, AgX : L (1 : n), a parallel series of complexes formed with silver(I) trifluoromethanesulfonate ('tfs', 'triflate') has been similarly defined, showing rather more divergence from tendencies established with the previous ClO(4), NO(3), F(3)CCO(2) core arrays than might be expected from basicity arguments. Thus, while silver triflate crystallised from neat base forms 1 : 2 mononuclear adducts with 2,4,6-trimethylpyridine and quinoline which comprise essentially linear two-coordinate [LAgL](+) cations, perturbed by approaches of the anions, 1 : 2 adducts obtained similarly from pyridine and 2-methylpyridine are [L(2)Ag(mu-tfs)(2)AgL(2)] dimers, with central four- and eight-membered rings arising from mu-OSO(2)CF(3) and extended mu-(O,O'SOCF(3)) anion bridging modes, respectively. With piperidine, a single-stranded polymer reminiscent of the arrays [(pip)(2)AgX](infinity/infinity), X = Cl, NCS, is formed, the triflate bridging through two of its oxygen atoms, rather than via a single atom bridge. With 2- and 4-cyanopyridine, the former a 1 : 1 adduct (being an acetonitrile solvate (MeCN coordinated)), and the latter 1 : 2, both are more complex structures in which the nitrile functionalities now coordinate weakly. The 1 : 2 adduct with 2-acetylpyridine parallels its perchlorate analogue, the ligands being bidentate in a mononuclear complex [L(2)AgOSO(2)CF(3)], while adducts of 2,9-dimethylphenanthroline and 2,2'-biquinolyl, both acetonitrile monosolvates, take the form [LAg(NCMe)]tfs. Agtfs : dpk (8 : 8)(infinity/infinity).EtOH ('dpk' = bis(2-pyridyl)ketone) is a complex polymer. The nature of the interactions is explored by way of spectroscopy (IR, NMR and ESI MS) and a density functional theory approach.

Abstract  The Transition State (TS) for any chemical glycosylation reaction is not known with certainty. Both experimental and computational approaches have been limited due to the complexity of the problem. This work describes a preliminary computational ionization approach using density functional theory calculations to arrive at hypothetical TSs. The new TSs contain the glycosyl donor as anomeric triflates, the acceptor as methanol, some CH(2)Cl(2) molecules, and a Li(+) ion promoter. In this computational approach all glycosylations are disassociative in that the C-1-O(Tf) bond length is greater then 2 Å before any nucleophilic attack. All nucleophilic attack requires some preassociation of the nucleophile with examples of the pre-attack complexation to donor oxygens. These hypothetical models are intended to guide both experimental and computational approaches to finding TSs for glycosylation reactions that can be used to optimize stereoselectivity of glycosylation.

Abstract  The palladium-catalyzed copolymerization of styrene and CO in an ionic liquid solvent, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, gave improved yields and increased molecular weights compared to polymerizations run in methanol.

Abstract  Glycosyl triflates, which serve as important intermediates in glycosylation reactions, were generated and accumulated by the low-temperature electrochemical oxidation of thioglycosides such as thioglucosides, thiogalactosides, and thiomannosides in the presence of tetrabutylammonium triflate (Bu(4)NOTf) as a supporting electrolyte. Thus-obtained solutions of glycosyl triflates (glycosyl triflate pools) were characterized by low-temperature NMR measurements. The thermal stability of glycosyl triflates and their reactions with glycosyl acceptors were also examined.

Abstract  For decades, triflic add, methyl triflate, and trialkylsilyl triflate reagents have served synthetic chemistry well as clean, strong electrophilic sources of H+, CH3+, and R3Si+, respectively. However, a number of weakly basic substrates are unreactive toward these reagents. In addition, triflate anion can express undesired nucleophilicity toward electrophilically activated substrates. s Account, we describe methods that replace triflate-based electrophilic reagents with carborane reagents. Using carborane anions of type CHB11R5X6- (R = H, Me, X; X = Br, Cl), members of a class of notably inert, weakly nucleophilic anions, significantly increases the electrophilicity of these reagents and shuts down subsequent nucleophilic chemistry of the anion. Thus, H(carborane) acids cleanly protonate benzene, phosphabenzene, C-60, etc., while triflic acid does not. Similarly, CH3(carborane) reagents can methylate substrates that are inert to boiling neat methyl triflate, including benzene, phosphabenzenes, phosphazenes, and the pentamethylhydrazinium ion, which forms the dipositive ethane analogue, Me6N22+. Methyl carboranes are also surprisingly effective in abstracting hydride from simple alkanes to give isolable carbocation salts, e.g., t-butyl cation. ylsilyl carborane reagents, R3Si(carborane), abstract halides from substrates to produce cations of unprecedented reactivity. For example, fluoride is extracted from freons to form carbocations; chloride is extracted from IrCl(CO)(PPh3)(2) to form a coordinatively unsaturated iridium cation that undergoes oxidative addition with chlorobenzene at room temperature; and silylation of cyclo-N3P3Cl6 produces a catalyst for the polymerization of phosphazenes that functions at room temperature. Although currently too expensive for widespread use, carborane reagents are nevertheless of considerable interest as specialty reagents for making reactive cations and catalysts.

Abstract  Suzuki-Miyaura cross-coupling reactions of aryl halides and triflates with potassium acetoxymethyltrifluoroborate afforded the corresponding aryl and heteroaryl methanol products in moderate to excellent yields.

Abstract  Solid octaaqua(kappa(2)O-perchlorato)thorium(IV) perchlorate hydrate, [Th(H(2)O)(8)(ClO(4))](ClO(4))(3)center dot H(2)O, 1, and aqua-oxonium hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) trisaquahexakis(kappa O-trifluoromethanesulfonato)-thorinate(IV), H(5)O(2)[Th(H(2)O)(6)(OSO(2)CF(3))(3)][Th(H(2)O)(3)(OSO(2)CF(3))(6)], 2, were crystallized from concentrated perchloric and trifluoromethanesulfonic acid solutions, respectively. 1 adopts a severely distorted tricapped trigonal prismatic configuration with an additional oxygen from the perchlorate ion at a longer distance. 2 consists of individual hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) and trisaquahexakis(kappa O-trifluoromethanesulfonato)thorinate(IV) ions and an aquaoxonium ion bridging these two ions through hydrogen bonding. The hydrated thorium(IV) ion is nine-coordinated in aqueous solution as determined by extended X-ray absorption fine structure (EXAFS) and large angle X-ray scattering (LAXS). The LAXS studies also showed a second hydration sphere of about 18 water molecules, and traces of a 3rd hydration sphere. Structural studies in aqueous solution of the hydrolysis products of thorium(IV) have identified three different types of hydrolysis species: a mu(2)O-hydroxo dimer, [Th(2)(OH)(2)(H(2)O)(12)](6+), a mu(2)O-hydroxo tetramer, [Th(4)(OH)(8)(H(2)O)(16)](8+), and a mu(3)O-oxo hexamer, [Th(6)O(8)(H(2)O)(n)](8+). Detailed structures of these three hydrolysis species are given A compilation of reported solid state structures of actinoid(IV) compounds with oxygen donor ligands show a strong correlation between the An-O bond distance and the coordination number. The earlier reported U-O bond distance in the hydrated uranium(IV) ion in aqueous solution, confirmed in this study, is related to nine-coordination. The hydrated tri- and tetravalent actinoid ions in aqueous solution all seem to be nine-coordinated The trivalent ions show a significant difference in bond distance to prismatic and capping water molecules in assumed tricapped trigonal prismatic configuration, while the tetravalent ions seem to form more regular structures, probably because of higher polarization.

Abstract  Aryldiazene complexes [Mn(CO)(3)(ArN=NH)P(2)]BF(4) (1, 2) and [{Mn(CO)(3)P(2)}(2)(&mgr;-HN=NArArN=NH)](BF(4))(2) (3, 4) [P = PPh(OEt)(2), PPh(2)OEt; Ar = C(6)H(5), 2-CH(3)C(6)H(4), 4-CH(3)C(6)H(4), 4-CH(3)OC(6)H(4); ArAr = 4,4'-C(6)H(4)C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)C(6)H(3)(2-CH(3)), 4,4'-C(6)H(4)CH(2)C(6)H(4)] were prepared by reacting hydride species MnH(CO)(3)P(2) with the appropriate aryldiazonium cations in CH(2)Cl(2) or acetone solutions at -80 degrees C. The compounds were characterized by IR, (1)H and (31)P NMR spectra (with (15)N isotopic substitution), and a single-crystal X-ray structure determination. The complex [Mn(CO)(3)(4-CH(3)C(6)H(4)N=NH){PPh(OEt)(2)}(2)]BF(4) (1c) crystallizes in the space group C2/c with a = 31.857(5) Å, b = 11.119(2) Å, c = 22.414(3) Å, beta = 97.82(1) degrees, and Z = 8. Treatment of aryldiazene compounds 1-4 with NEt(3) gave the pentacoordinate aryldiazenido [Mn(CO)(2)(ArN(2))P(2)] (5, 6) and [{Mn(CO)(2)P(2)}(2)(&mgr;-N(2)ArArN(2))] (7, 8) [P = PPh(OEt)(2), PPh(2)OEt; Ar = C(6)H(5), 4-CH(3)C(6)H(4); ArAr = 4,4'-C(6)H(4)C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)C(6)H(3)(2-CH(3))] derivatives. Protonation reactions of these aryldiazenido complexes 5-8 with HCl afforded the aryldiazene [MnCl(CO)(2)(ArN=NH)P(2)] (9) and [{MnCl(CO)(2)P(2)}(2)(&mgr;-HN=NArArN=NH)] (10) derivatives. Hydrazine complexes [Mn(CO)(3)(RNHNH(2))P(2)]BPh(4) (11, 12) [P = PPh(OEt)(2), PPh(2)OEt; R = H, CH(3), C(6)H(5), 4-NO(2)C(6)H(4)] were prepared by allowing hydride species MnH(CO)(3)P(2) to react first with triflic acid and then with the appropriate hydrazine. Their characterization by IR, (1)H and (31)P NMR spectra, and an X-ray crystal structure determination is reported. The compound [Mn(CO)(3)(NH(2)NH(2)){PPh(OEt)(2)}(2)]BPh(4) (11a) crystallizes in the space group P&onemacr; with a = 13.772(3) Å, b = 14.951(4) Å, c = 13.319(3) Å, alpha = 104.47(1) degrees, beta = 100.32(1) degrees, gamma = 111.08(1) degrees, and Z = 2. Oxidation reactions of hydrazine compounds 11 and 12 with Pb(OAc)(4) at -40 degrees C gave stable aryldiazene [Mn(CO)(3)(RN=NH)P(2)]BPh(4) and thermally unstable (upon reaching -40 degrees C) diazene [Mn(CO)(3)(HN=NH)P(2)]BPh(4) derivatives.

Abstract  The article discusses the methods for the preparation of antigens containing N-acetylglucosamine residues glycosylated at O-4. It discusses the synthesis of alkyl imidate protected glucosamine acceptors at position 4 and various protecting groups at O-3. It infers that alkyl imidate products were readily converted to their corresponding N-acetyl derivatives under mild conditions in all cases. Glycosylation reaction via alkyl imidate protected acceptor intermediates is also presented.

Abstract  The effect of salt concentration on the ubiquitous ionic interactions observed in the case of the silver ion conducting polymer electrolyte system poly(propylene glycol) (PPG)-silver triflate has been investigated using Fourier transform infrared (FT-IR) spectroscopy as a probe for the characterization of the local environment of the triflate ion in PPG-based polymer electrolytes. The maximum free anion concentrations of symmetric and asymmetric SO(3) stretching modes in the case of poly(propylene glycol) complexed with silver triflate (AgCF(3)SO(3)) corresponding to the ether oxygen metal cation ratios from 2:1 to 6:1 have been investigated in detail. The present Fourier transform infrared spectral studies of the C-O-C stretching mode have shown reduction in the intensity, due to the decrease of salt concentration. The splitting of vibrational modes has been analyzed in terms of free ions, ion pairs and aggregates. The bands of SO(3) symmetric stretching mode appearing at 1032 and 1038 cm(-1) in the chosen polymer electrolyte material have been assigned to free ions and ion pairs respectively.

Abstract  Triflic acid is a functional group of perflourosulfonated polymer electrolyte membranes where the sulfonate group is responsible for proton conduction. However, even at extremely low hydration, triflic acid exists as a triflate ion. In this work, we have developed a force-field for triflic acid and triflate ion by deriving force-field parameters using ab initio calculations and incorporated these parameters with the Optimized Potentials for Liquid Simulations - All Atom (OPLS-AA) force-field. We have employed classical molecular dynamics (MD) simulations with the developed force field to characterize structural and dynamical properties of triflic acid (270-450 K) and triflate ion/water mixtures (300 K). The radial distribution functions (RDFs) show the hydrophobic nature of CF(3) group and presence of strong hydrogen bonding in triflic acid and temperature has an insignificant effect. Results from our MD simulations show that the diffusion of triflic acid increases with temperature. The RDFs from triflate ion/water mixtures shows that increasing hydration causes water molecules to orient around the SO(3)(-) group of triflate ions, solvate the hydronium ions, and other water molecules. The diffusion of triflate ions, hydronium ion, and water molecules shows an increase with hydration. At λ = 1, the diffusion of triflate ion is 30 times lower than the diffusion of triflic acid due to the formation of stable triflate ion-hydronium ion complex. With increasing hydration, water molecules break the stability of triflate ion-hydronium ion complex leading to enhanced diffusion. The RDFs and diffusion coefficients of triflate ions, hydronium ions and water molecules resemble qualitatively the previous findings using per-fluorosulfonated membranes.

Abstract  Contribution of cytotoxic T lymphocytes (CTL) to experimental autoimmune thyroiditis (EAT) was well defined (Speidel et al., Eur. J. Immunol. 1997, 27, 2391-2399, Ref. 7). The native porcine thyroglobulin (pTg) showed high sensitivity to endo-o-N-acetylglucosaminidase F (Endo F) and its molecular weights, corresponding to about 330 kDa as a monomer and 660 kDa as a dimer, were reduced to smaller molecular weight forms by Endo F and trifluoromethanesulfonic acid (TMSF). Deglycosylated porcine Tg (dgpTg) and native pTg were injected i.v. into CBA/J mice, without the aid of adjuvants. Both lymphocytic infiltrations of the thyroid glands and levels of Tg-specific CTL were similar to those found in conventional EAT induced by Tg and adjuvants. In contrast, proliferative responses in native pTg and dgpTg-injected mice could not be detected, and titers of antibodies to pTg and dgpTg were 20 times and 30 times lower than that of pTg and adjuvants, respectively. The EAT-inducer CTL belonged to the CD8+ cell subset and exerted their thyroiditogenic potential through release of IFN-gamma. It was concluded that dgpTg-induced EAT is mediated by type 1 cytotoxic T cells (Tcl). Also, results that EAT induction of the glycosylated pTg (gpTg) was much lower than that of dgpTg, suggested that the abberant and incomplete glycosylation of the thyroglobulin is responsible for the induction of autoimmune thyroiditis.

Abstract  The presence of persistent and mobile organic contaminants (PMOC) in aquatic environments is a matter of high concern due to their capability of crossing through natural and anthropogenic barriers, even reaching drinking water. Most analytical methods rely on reversed-phase liquid chromatography (RPLC), which is quite limited for the detection of very polar chemicals. Thus, many of these PMOCs may have not been recognized as water pollutants yet, due to the lack of analytical methods capable to detect them. Mixed-mode LC (MMLC), providing the combination of RP and ion-exchange functionalities is explored in this work with a trifunctional column, combining RPLC, anion and cation exchange, which allows the simultaneous determination of analytes with extremely different properties. A nondiscriminant sample concentration step followed by a MMLC-high resolution mass spectrometry method was developed for a group of 37 very polar model chemicals with different acid/base functionalities. The overall method performance was satisfactory with a mean limit of detection of 50 ng/L, relative standard deviation lower than 20% and overall recoveries (including matrix effects) higher than 60% for 54% of model compounds. Then, the method was applied to 15 real water samples, by a suspect screening approach. For those detected PMOC with standard available, a preliminary estimation of concentrations was also performed. Thus, 22 compounds were unequivocally identified in a range of expected concentrations from 6 ng/L to 540 μg/L. Some of them are well-known PMOC, such as acesulfame, perfluorobutanoic acid or metformin, but other novel pollutants were also identified, as for example di-o-tolylguanidine or trifluoromethanesulfonic acid, which had not or were scarcely studied in water so far.

Abstract  Triflic acid (HOTf)-bound nonheme Mn(IV)-oxo complexes, [(L)Mn(IV)(O)](2+)-(HOTf)2 (L = N4Py and Bn-TPEN; N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) and Bn-TPEN = N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine), were synthesized by adding HOTf to the solutions of the [(L)Mn(IV)(O)](2+) complexes and were characterized by various spectroscopies. The one-electron reduction potentials of the Mn(IV)(O) complexes exhibited a significant positive shift upon binding of HOTf. The driving force dependence of electron transfer (ET) from electron donors to the Mn(IV)(O) and Mn(IV)(O)-(HOTf)2 complexes were examined and evaluated in light of the Marcus theory of ET to determine the reorganization energies of ET. The smaller reorganization energies and much more positive reduction potentials of the [(L)Mn(IV)(O)](2+)-(HOTf)2 complexes resulted in much enhanced oxidation capacity towards one-electron reductants and para-X-substituted-thioanisoles. The reactivities of the Mn(IV)-oxo complexes were markedly enhanced by binding of HOTf, such as a 6.4 × 10(5)-fold increase in the oxygen atom transfer (OAT) reaction (i.e., sulfoxidation). Such a remarkable acceleration in the OAT reaction results from the enhancement of ET from para-X-substituted-thioanisoles to the Mn(IV)(O) complexes as revealed by the unified ET driving force dependence of the rate constants of OAT and ET reactions of [(L)Mn(IV)(O)](2+)-(HOTf)2. In contrast, deceleration was observed in the rate of H-atom transfer (HAT) reaction of [(L)Mn(IV)(O)](2+)-(HOTf)2 complexes with 1,4-cyclohexadiene as compared with those of the [(L)Mn(IV)(O)](2+) complexes. Thus, the binding of two HOTf molecules to the Mn(IV)(O) moiety resulted in remarkable acceleration of the ET rate when the ET is thermodynamically feasible. When the ET reaction is highly endergonic, the rate of the HAT reaction is decelerated due to the steric effect of the counter anion of HOTf.