Synthesis And Structural Characterisation Of [ir4(co)8(ch3)(μ4-η 3-ph2pccph)(μ-pph2)] And Of The Carbonylation Product [ir4(co)8{c(o)ch3}(μ4-η 3-ph2pccph)(μ-pph2)]

Deprotonation of [(μ-H)Ir4(CO)10(μ-PPh2)], 1, gives [Ir4(CO)10(μ-PPh2)]- that reacts with Ph2PCCPh and CH3I to afford [Ir4(CO)8(CH3)(μ4-η 3-Ph2PCCPh)(μ-PPh2)], 2 (34%), besides [Ir4(CO)9(μ3-η3-Ph 2PC(H)CPh)(μ-PPh2)] and [(μ-H)Ir4(CO)9(Ph2PC≡CPh)(μ-PPh2)]. Compound 2 was characterised by a single crystal X-ray diffraction analysis and exhibits a flat butterfly of metal atoms, with the Ph2PCCPh ligand interacting with all four Ir atoms and the methyl group bonded terminally to a wingtip Ir atom. Carbonylation of 2 yields initially (25°C, 20 min) a CO addition product that, according to VT 31P{1H} and 13C{1H} studies, exists in solution in the form of two isomers 4A and 4B (8:1), and then (40°C, 7 h), the CO insertion product [Ir4(CO)8{C(O)CH3}-(μ4-η 3-Ph2PCCPh)(μ-PPh2)], 5. The molecular structure of 5, established by an X-ray analysis, is similar to that of 2, except for the acyl group that remains bound to the same Ir atom. The process is reversible at both stages. Treatment of 2 with PPh3 and P(OMe)3 affords the CO substitution products [Ir4(CO)7L(CH3)(μ4-η 3-Ph2PCCPh)(μ-PPh2)] (L = PPh3, 6 and P(OMe)3, 7), instead of the expected CO inserted products. According to the 1H and 31P{1H} NMR studies, the PPh3 derivative 6 exists in the form of two isomers (1:1) that differ with respect to the position of this ligand.1013545Hoffmann, R., (1982) Angew. Chem. Int. Ed. Engl., 21, p. 711Bau, R., Chiang, M.Y., Wei, C.-Y., Garlaschelli, L., Martinengo, S., Koestzle, T.F., (1984) Inorg. Chem., 23, p. 4758Ragaini, F., Porta, F., Demartin, F., (1991) Organometallics, 10, p. 185Albano, V.G., Canziani, F., Ciani, G., Chini, P., Martinengo, S., Manassero, M., Giordano, G., (1978) J. Organomet. Chem., 150, pp. C17Chinara, T., Aoki, K., Yamazaki, H., (1990) J. Organomet. Chem., 353, p. 367Chinara, T., Aoki, K., Yamazaki, H., (1994) J. Organomet. Chem., 473, p. 273González-Moraga, (1993) Cluster Chemistry, , Chapter 3, Springer-Verlag, BerlinBenvenutti, M.H.A., Vargas, M.D., Braga, D., Grepioni, F., Parisini, E., Mann, B.E., (1993) Organometallics, 12, p. 2955Benvenutti, M.H.A., Vargas, M.D., Braga, D., Grepioni, F., Mann, B.E., Naylor, S., (1993) Organometallics, 12, p. 2947Yamamoto, A., (1986) Organotransition Metal Chemistry, , WileyMorison, E.D., Bassner, L.S.L., Geoffroy, G.L., (1986) Organometallics, 5, p. 408Pereira, R.M.S., Fujiwara, F.Y., Vargas, M.D., Braga, D., Grepioni, F., (1997) Organometallics, 16, p. 4833Delgado, E., Chi, Y., Wang, W., Horgath, G., Low, P.J., Enright, G.D., Peng, S.-M., Carty, A.J., (1998) Organometallics, 17, p. 2936Vargas, M.D., Pereira, R.M.S., Braga, D., Grepioni, F., (1993) J. Chem. Soc. Chem. Commun., p. 1008Hengefelt, A., Nast, R., (1983) Chem. Ber., 116, p. 2025Livotto, F.S., Raithby, P.R., Vargas, M.D., (1993) J. Chem. Soc. Dalton Trans., p. 1797Brauer, G., (1965) Handboock of Preparative Inorganic Chemistry, 1, p. 645Sheldrick, G.M., (1990) Acta Crystallogr., A46, p. 467Sheldrick, G.M., (1976) SHELX76, Program for Crystal Structure Determination, , University of Cambridge, Cambridge, EnglandWalker, N., Stuart, D., (1983) Acta Crystallogr., Sect. B, 39, p. 158Keller, E., (1992) SHAKAL92, Graphical Representation of Molecular Models, , University of Freiburg, FRGKubota, M., McClesky, T.M., Hayashi, R.K., Carl, G., (1987) J. Am. Chem. Soc., 109, p. 7569Wade, K., (1976) Adv. Inorg. Chem. Radiochem., 18, p. 1Benvenutti, M.H.A., Vargas, M.D., Hitchcock, P.B., Nixon, J.F., (1995) J. Chem. Soc. Chem. Commun., p. 866Carty, A.J., Mac Laughlin, S.A., Nucciaroni, D., (1987) Phosphorus 31-NMR Spectroscopy in Steereochemical Analysis of Organic Compounds and Metal Complexes, , Chapter 16Verkade, J. G.Quin, L. D. EdsVCHKeister, J.B., (1980) J. Organomet. Chem., 190, pp. C36Aime, S., Dastrù, W., Gobetto, R., Viale, A., (1998) Organometallics, 17, p. 3182Johnson, B.F.G., Lewis, J., Orpen, A.G., Raithby, P.R., Süss, G., (1979) J. Organomet. Chem., 173, p. 187Araujo, M.H., Vargas, M.D., unpublished resultsMonti, D., Frachey, G., Bassetti, M., Haynes, A., Sunley, G.J., Maitlis, P.M., Cantoni, A., Bocelli, G., (1995) Inorg. Chim. Acta, 240, p. 485Garcia Alonso, J., Llamazares, A., Riera, V., Diaz, M.R., García Grande, S., (1991) J. Chem. Soc. Chem. Commun., p. 1058Cotton, J.D., Crisp, G.T., Daly, V.A., (1981) Inorg. Chim. Acta, 47, p. 165Bondietti, G., Laurenczy, G., Ross, R., Roulet, R., (1994) Helv. Chim. Acta, 77, p. 1869Laurenczy, G., Bondietti, G., Merbach, A.E., Moulet, B., Roulet, R., (1994) Helv. Chim. Acta, 77, p. 547Braga, D., Grepioni, F., Vargas, M.D., Ziglio, C.M., manuscript in preparatio

Reaction Of [fe3(co)12] With Bidentate Phosphines: Redox Behavior Of Products

The reactions of [Fe3(CO)12] with the bidentate phosphines 1,2-bis(diphenylphosphino)ethane (dppe), 1,4-bis(diphenylphosphino)butane (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppf) and 1,4-bis(diphenylphosphino)benzene (dppbz) using trimethylamine N-oxide as decarbonylating agent produce the chelated [Fe3(CO)8(μ-CO)2(μ,η2-diphosphine)] and the new series of symmetrical [{Fe3(CO)9(μ,-CO)2}2(μ,η2-diphosphine)] and unsymmetrical [Fe3(CO)9(μ-CO)2](μ,η2-diphosphine)[Fe(CO)4] bridged complexes, in reasonable yield. The complexes were characterized by IR, 31P and 13C NMR spectroscopy, and elemental analysis. Electrochemical studies on these compounds reveal that the substitution of one or more phosphine ligands for carbon monoxide of [Fe3(CO)12] results in a more cathodic potential for the first reduction peak, but is insensitive to the σ-donor capabilities of the ligands.5251-23137Bruce, M.I., (1987) Coord. Chem. Rev., 76, p. 1Shiu, K.B., Peng, S.M., Cheng, M.C., (1993) J. Organomet. Chem., 453, p. 133Deeming, A.J., Johnson, B.F.G., Lewis, J., (1970) J. Chem. Soc. (A), p. 897Tachikawa, N., Shapley, J.R., (1977) J. Organomet. Chem., 124, pp. C19Bruce, M.I., Khoe, D.C., Matisons, J.G., Nicholson, B.K., Rieger, P.H., Williams, M.L., (1982) J. Chem. Soc., Chem. Commun., p. 442Deeming, A.J., Donovan-Mtunzi, S., Kabir, S.E., (1984) J. Organomet. Chem., 276, pp. C65Adams, C.J., Bruce, M.I., Horn, H., Shelton, B.W., Tiekeisk, E.R.T., White, A.H., (1993) J. Chem. Soc., Dalton Trans., p. 3299Amoroso, A.J., Johnson, B.F.G., Lewis, J., Massey, A.D., Raythby, P.R., Wong, W.T., (1992) J. Organomet. Chem., 440, p. 219Shen, J.K., Gao, Y.C., Shi, Q.Z., Basolo, F., (1988) Inorg. Chem., 27, p. 4236Angelici, R.J., Siefert, E.E., (1966) Inorg. Chem., 5, p. 1457Perin, D.D., Armarego, W.L.F., Perin, D.R., (1980) Purification of Laboratory Chemicals, , Pergamon Press, New York, 2nd ednKim, T.J., Kwon, K.H., Kwon, S.C., Baeg, J.O., Shim, S.C., Lee, D.H., (1990) J. Orgonomet. Chem., 389, p. 205Kim, T.J., Kwon, S.C., Kim, Y.H., Heo, N.H., Teeter, M.M., Yamano, A., (1991) J. Organomet. Chem., 426, p. 71Keiter, R.L., Rheingold, A.L., Hmerski, J.J., Castle, C.K., (1983) Organometallics, 2, p. 1635Farrar, D.H., Lunniss, J.A., (1987) J. Chem. Soc., Dalton Trans., p. 1249Adams, H., Bailey, N.A., Bentley, G.W., Mann, B.E., (1989) J. Chem. Soc., Dalton Trans., p. 1831Murr, N.E., Chaloyard, A., (1982) Inorg. Chem., 21, p. 2206Bond, A.M., Dawson, P.A., Peake, B.M., Robinson, B.H., Simpson, J., (1977) Inorg. Chem., 16, p. 2199Fantucci, P., (1992) Inorg. Chem., 13, p. 241Richmond, M.G., Kochi, J.K., (1986) Inorg. Chem., 25, p. 656Pickett, C.J., Pletcher, D., (1975) J. Organomet. Chem., 102, p. 327Connor, J.A., Jones, E.M., McEwen, G.K., Lloyd, M.L., McCleverty, J.A., (1972) J. Chem. Soc., Dalton Trans., p. 1246Triechel, P.M., Duncan, G.E., Haub, H.J., (1972) J. Organomet. Chem., 44, p. 339Dessy, R.E., Bares, L.E., (1972) Acc. Chem. Res., 5, p. 41

Mesophase Behavior And Structure Of Type I Lyotropic Liquid Crystals

Mesophases prepared from binary mixtures (detergent/water) and ternary mixtures (detergent/water/electrolyte) have been investigated as a function of water content and temperature by studying deuterium magnetic resonance of the heavy water and in some cases deuterated hydrocarbon segments. The binary mixtures cover the region of H α hexagonal mesophase formation, and at higher water contents these mixtures pass directly to isotropic phases, with which they may coexist in equilibrium. With the addition of small amounts of electrolyte, the intermediate nematic type I Δx > 0 mesophase is formed in all three cases investigated. In the region of coexistence with H α mesophases, both uniaxial liquid crystals have been shown to be type I; the hexagonal phase aligns over a period of about 1 week with the director along the direction of the magnetic field. The variation of temperature causes large variations of order in the intermediate nematic mesophase, which has been named "CM" type I for cylindrical micellar nematic mesophase. At high temperatures coexistence regions of H α and CM mesophases are found. A sequence of structures is proposed, where a concentrated isotropic micellar phase of rodlike micelles passes, as water content is decreased, into a region of type I properties for the CM mesophase in which there is long-range orientational order but no positional order of the micelles. In cases where the CM mesophase coexists with the H α phase, a nucleation of two degrees of positional degrees of order is postulated. The sequence of mesophases derived from La structures of lamellar form is somewhat analogous. In the concentrated micellar solutions the micelles can be disklike but isotropically tumbling entities which gain orientational order at lower water contents. These "DM" disk micelle nematic mesophases are type II in magnetic anisotropy and nucleate out regions of the L α mesophase which has one degree of positional order. Low-angle X-ray diffraction indicates a lack of positional long-range order in both type II and type I, DM and CM nematic mesophases, respectively. In a system which undergoes a transition from a type I CM nematic to a type II DM nematic mesophase, the covariation of the quadrupole splitting of deuterium in water and the hydrocarbon chain segments -CD 2- near the interface shows that the relative motions at these different locations are unchanged by the curvature of the interface. The degree of order profile of the perdeuterated laurate chain in L α, DM, H α, and CM mesophases has been compared. Although the condition of constant surface area of the detergent at the interface cannot be preserved, there are notable similarities and differences in the ratios of some segment CD 2 splittings which have been associated with the interface curvature and host/guest interactions. © 1980 American Chemical Society.84665366

Assignment Of 13c Nmr Data Of Methyl (+)-hardwickiate And Its Derivatives

Despite the large number of clerodanes isolated as natural products in the last decade, the correct 13C NMR chemical shift assignments of some carbons are still in doubt. In order to provide unambiguous assignments of the chemical shifts of clerodane diterpenes, a complete 13C NMR spectral analysis of methyl (+)-hardwickiate and 14 hemisynthetic derivatives is reported. © 1998 John Wiley & Sons, Ltd.367542544Imamura, P.M., Pantarotto, H., (1995) Liebigs Ann., p. 1891Sharma, S.C., Tandon, J.S., Porter, B., Raju, M.S., Wenkert, E., (1984) Phytochemistry, 23, p. 1194Lu, T., Vargas, D., Franzblau, S.G., Fischer, N.H., (1995) Phytochemistry, 38, p. 451Wehrli, F.W., Wirthlin, T., (1980) Interpretation of Carbon-13 NMR Spectra, , Heyden, LondonBreitmaier, E., Voelter, W., (1987) Carbon-13 NMR Spectroscopy, , VCH, WeinheimBuckwalter, B.L., Burfitt, I.R., Nagel, A.A., Wenkert, E., Näf, F., (1975) Helv. Chim. Acta, 58, p. 1567De Rosa, S., Minale, L., Riccio, R., Sodano, G., (1976) J. Chem. Soc. Perkin Trans, 1, p. 1408Rudi, A., Koshman, Y., (1992) J. Nat. Prod., 55, p. 1408Spanevello, R.A., Vila, A.J., (1994) Phytochemistry, 35, p. 537Hao, X.-J., Yang, X.-S., Zhang, Z., Shang, L.-J., (1995) Phytochemistry, 39, p. 44

Wood Adhesives From Eucalyptus Tar And Creosote [alcatrão Ou Creosoto De Eucalipto Na Produção De Adesivos Fenólicos Para Colagem De Madeira]

This study has shown that Eucalyptus tar and creosote can be used in phenolic adhesive formulations (resols) for wood products bonding. Some adhesives were prepared substituting 0; 17.7; 35.0 and 67.0% of the phenol by anhydrous tar and 0; 15.0 e 28.5% by creosote. In gluing Brazilian pine veneers, eucalypt tar and creosote based adhesives required longer pressing times for curing than conventional phenol-formaldehyde adhesives. By using 13C NMR, the number of carbons in side chains and hydroxyl, carbonyl, carboxyl and methoxyl groups related to 100 aromatic rings could be estimated in tar and creosote. In creosote, after reaction with excess formaldehyde in alkaline medium, only 0,28 hydroxymethyl groups was detected per phenolic ring. This low amount of hydroxymethylation explains the lack of reactivity in curing observed when creosote was introduced in a standard adhesive formulation.204365371Christiansen, A.W., Gollob, L., (1985) J. Appl. Polymer Sci., 30, p. 2279Keinert Jr., S., Wolf, F., (1984) Alternativas de Adesivos à Base de Taninos para Madeira, p. 25. , Curitiba, FUPEF, Série TécnicaLewis, N.G., Lantzy, T., (1989) Adhesives from Renewable Resources Washington, pp. 96-109. , American Chemical Society ACS symposium seriesDolenko, A.J., Clarke, M.R., (1978) Forest Products Journal, 28, p. 41Pizzi, A., (1994) Advanced Wood Adhesives Technology, , New York, Marcel DekkerChum, H., Diebold, J., Scahill, J., Thompson, D., Black, S., Sdhroeder, H., Kreibich, R.E., (1989) Adhesives from Renewable Resources, pp. 135-151. , American Chemical Society.ACS, Washington, ACS symposium seriesSantos, C.G., Laranjeira, A.D., Carazza, F., (1988) Quím. Nova, 11, p. 284Pasa, V.M.D., Otani, C., Carazza, F., (1993) Proceedings of the 3re Brazilian Symposium of Lignins and Other Wood Components, 4. , Belo HorizontePasa, V.M.D., (1994) Piche Do Alcatrão de Eucalyptus: Obtenção, Caracterização e Desenvolvimento de Aplicações, , Imprensa Universitária - UFMG, Belo Horizonte, Tese de DoutoramentoCampbell, A.G., Walsh, A.R., (1985) J. Adhesion, 18, p. 301Elder, T.J.J., (1979) The Caracterization and Potential Utilization of the Phenolic Compounds Found in a Pyrolitic Oil, 91p. , Texas, A & M University, Tese de DoutoramentoMaciel, A.S., (1989) Produção de Adesivos a Partir de Derivados Fenólicos de Alcatrão Vegetal, 89p. , Viçosa, MG, UFV, Dissertação de MestradoWenzil, H.F.J., (1970) The Chemical Technology of Wood, , John Wiley e Sons, New YorkGillespie, R.H., (1989) Adhesives from Renewable Resources, pp. 135-151. , American Chemical Society. ACS, Washington, ACS symposium seriesPimenta, A.S., Vital, B.R., Brazilian Patent. INPI - PI 9502117-5, publicada 19/05/95(1994) Annual Book of Standards, , WashingtonMaarton, J., Marton, T., Falkehag, S.I., Adler, E., (1966) Adv. Chem. Ser., 59, p. 12

Structural And Electronic Effects In (benzylideneacetone)dicarbonyl(phosphine)iron(0) And (benzylideneacetone)dicarbonyl(phosphite)iron(0) Complexes. A Carbon-13 Magnetic Resonance Study

The structures in solution and the electronic effects induced by the ligands L in the series (benzylideneacetone) Fe(CO)2L (L = CO, tertiary phosphines, and tertiary phosphites) were studied by 13C NMR spectroscopy. In contrast to the tricarbonyl derivative, which is fluxional at 32°C, the compounds containing a phosphorus ligand do not show fluxional behavior at this temperature. This could be attributed to an increase in the π back-donation from the filled metal d orbitals to the LUMO of benzylideneacetone (BDA) induced by the better σ-donor and poorer π-acceptor phosphorus ligands, compared to CO. The resonances of coordinated BDA show a very large upfield shift at the carbons directly involved in bonding with iron. The differences in the chemical shifts at the terminal carbon of the heterodiene function in coordinated and free BDA, AC4, correlate reasonably well with the basicities of the phosphorus ligands while the ratio ΔC4/ΔC3 correlates with the Tolman electronic parameter, v, of the phosphorus ligands. The results are interpreted on the basis of a bonding model in which the coordinated BDA acts as a "sink" for the negative charge placed in the iron atom by the phosphorus ligand via a P →σ Fe →α BDA mechanism. © 1985 American Chemical Society.24328629

Order Profiles Of Host Decyl Sulfate And Decylammonium Chains And Guest Carboxylic Acids And Carboxylates In Allgned Type Ii Dm Lyomesophases

Lyotropic liquid crystals type II (DM) have been synthesized from sodium decyl sulfate, decanol, water, and sodium sulfate with low concentrations of lauric, palmitic, and stearic acids and their conjugate anions. A wide variation of specifically deuterated decyl sulfate chains has been incorporated in low concentration as well as perdeuterated decyl sulfate, carboxylic acids, and their anions. Degrees of order profiles have been extracted from the study of deuterium quadrupole splittings in the corresponding NMR spectra of aligned mesophases. The ratios of segmental order along the C-D bonds for host decyl sulfate chains are independent of water content (within the region of the DM phase), a temperature variation of 3 °C, and the presence of small quantities of the guest amphiphiles. The invariance of the kink/jog motions in the decyl sulfate chain as the water content is varied has been interpreted in terms of the invariance in internal packing of host chains inside the disk micelle as these entities are diluted with more interstitial water. The decrease in absolute degrees of order of the decyl sulfate segments as water is added can be explained by increases in the amplitude of micelle motion because the water layer is increased in thickness and perhaps also because the mean disk diameter may decrease with added water. The guest amphiphile chains do not conform in length to the half bilayer thickness of the disk micelle. Several types of behavior have been noted: (a) The guest head group anchoring at the interface determines the form of the order profile of the guest chain to a very large extent within the half bilayer distance; i.e., the form of the order profiles near the anchored end depends on the head group and not on the chain length for long chains, (b) The guests are uniformly of higher order in the first segments at the impurity site than the host segments which form the solvent bilayer. (c) In the case of carboxylic acid guests, the degree of order profile in the region of high probability for single gauche rotations follows very closely that of the solvent SDS/decanol bilayer. (d) The degree of order profiles of carboxylate guests, on the other hand, are quite distinct from the host segments. A higher order of the guest chains persists well beyond the half bilayer distance, (e) A third situation arises for carboxylic acid guests in a decylammonium chloride type II DM mesophase. In this case the fall in order of the guest chains occurs well wiithin the plateau region of the host chains, (f) The excess chain lengths of palmitic, myristic, and stearic acids and anions participate in the disordered region at the center of the disk bilayer structure having low and steadily decreasing order. Nevertheless, the ratio of CD 2 to CD 3 splitting the nonpolar end of the chain falls close to a theoretical ratio of 3 for a rigid chain for the anion guests. © 1980 American Chemical Society.84666267

Tif4 Varnish - A 19f-nmr Stability Study And Enamel Reactivity Evaluation

The aim of this study was to develop a titanium tetrafluoride (TiF 4) varnish and evaluate the stability of the formulation and its reactivity with dental enamel. The varnish was prepared in a resinous matrix using ethanol 96% as solvent. Samples (n=45) were aged at 65°C and 30% of relativity humidity (RE n°01/05 - ANVISA) and after 3, 6, 9 and 12 months, nine samples were removed for evaluation and compared with fresh samples. Chemical stability of TiF4 varnish was determinate by 19F-NMR and the reactivity of the formulation was quantified by formation of fluoride loosely (CaF2) and firmly bound (fluorapatite; FA) to enamel. For reactivity comparisons, a varnish without TiF4 was used as control. The loss of soluble fluoride was about 0.9% after one year of storage. The values of the reactivity (mean±S.D.) of fresh, aged at 3, 6, 9 and 12 months and control samples were: CaF2 (μgF/mm 2): 89.3±27.5a; 54.5±14.3b; 51.2±29.8b; 69.3±21.3a; 48.0±27. 4b; 0.10±0.07c, FA (μg F/g): 2477.5±1044.0a; 2484.8±992.0a; 2580.0±1383.9a; 2517.2±929.9a; 2121.0±1059.2a; 330.0±180.0b, respectively. Means followed by distinct letters were statistically different (p<0.05). After one year of storage, the formulation was chemically stable and the levels of FA were maintained. However there was an initial decrease in the ability to form CaF2. © 2008 Pharmaceutical Society of Japan.561139141Shrestha, B.M., Mundorff, S.A., Basil, G.B., (1972) J. Dent. Res, 51, pp. 1561-1566Vieira, A., Ruben, J.R., Huysmans, M.C., (2005) Caries Res, 39, pp. 371-379Laptash, N.M., Fedotov, M.A., Maslennikova, I.G., (2004) J. Struct. Chem, 45, pp. 74-82Buslaev, Y.A., Dyer, D.S., Ragsdale, R.O., (1967) Inorg. Chem, 6, pp. 2208-2212Curzon, M.E.J., Cutress, T.W., (1983) Trace Elements and Dental Disease, , ed. by Wright J, PSG Inc, BristolRagsdale, R.O., Stewart, B.B., (1963) Inorg. Chem, 2, pp. 1002-1004Wei, S.H.Y., Soboroff, D.M., Wefel, J.S., (1976) J. Dent. Res, 55, pp. 426-431Marion, S.P., Thomas, A.W., (1946) J. Colloid. Sci, 1, pp. 221-234ANVISA - Resolution RE no 1, July 29, 2005. Available in: http://elegis.anvisa.gov.br/leisref/public/showAct.php?id=18109&word=, Access in November, 2005Calavaska, V., Moreno, E.C., Brudevold, F., (1975) Arch. Oral. Biol, 20, pp. 333-339Marinho, V.C.C., Higgins, J.P.T., Logan, S., Sheiham, A., (2006) The Cochrane Library, (4). , Oxford: Update SoftwareMarinho, V.C.C., Higgins, J.P.T., Logan, S., Sheiham, A., (2006) The Cochrane Library, (4). , Oxford: Update SoftwareMarinho, V.C.C., Higgins, J.P.T., Logan, S., Sheiham, A., (2006) The Cochrane Library, (4). , Oxford: Update SoftwareMarinho, V.C.C., Higgins, J.P.T., Logan, S., Sheiham, A., (2006) The Cochrane Library, (4). , Oxford: Update SoftwareDyer, D.S., Ragsdale, R.O., (1969) Inorg. Chem, 8, pp. 1116-1120Ragsdale, R.O., Stewart, B.B., (1964) Proc. Chem. Soc, 1964, p. 194Ögaard, B., (2001) Caries Res, 35, pp. 40-44White, D.J., Nancollas, G.H., (1990) J. Dent. Res, 69, pp. 587-594Dyer, D.S., Ragsdale, R.O., (1967) Inorg. Chem, 6, pp. 8-11Serre, C., Corbiere, T., Lorentz, C., Taulelle, F., Férey, G., (2002) Chem. Mater, 14, pp. 4938-494

Tuning The Acidic Properties Of Aluminas Via Sol-gel Synthesis: New Findings On The Active Site Of Alumina-catalyzed Epoxidation With Hydrogen Peroxide

This study answers several pending questions about alumina-catalyzed epoxidation with aqueous 70 wt% H2O2. To evaluate the effect of the water-to-aluminum tri-sec-butoxide molar ratio, this was systematically changed from 1 to 24. The xerogels were calcined at 450 °C and gave different γ-Al2O3's with distinct textural and acidic properties. A combination of 27Al MAS NMR and TPD-NH3 results of calcined aluminas allowed us to assign the type Ia Al{single bond}OH sites as the catalytic sites for epoxidation. The type Ib Al{single bond}OH sites have no function in catalytic epoxidation, because ethyl acetate poisons these sites. The strong acid sites of types IIa, IIb, and III Al{single bond}OH groups are responsible for the undesired H2O2 decomposition and decreased oxidant selectivity. © 2006 Elsevier Inc. All rights reserved.244192101Thornton, J., (2001) Pure Appl. Chem., 73, p. 1231Graedel, T.E., (2001) Pure Appl. Chem., 73, p. 1243Ward, D.K., Ko, E.I., (1995) Ind. Eng. Chem. Res., 34, p. 421Schubert, U., Hüsing, N., (2000) Synthesis of Inorganic Materials, , Wiley-VCH, Weinheim p. 205Dumeignil, F., Sato, K., Imamura, M., Matsubayashi, N., Payen, E., Shimada, H., (2005) Appl. Catal. A Gen., 287, p. 135Trueba, M., Trasatti, S.P., (2005) Eur. J. Inorg. Chem., p. 3393Grabowska, H., Syper, L., Zawadzki, M., (2004) Appl. Catal. A Gen., 277, p. 91Kim, Y., Kim, C., Yi, J., (2004) Mater. Res. Bull., 39, p. 2103Valente, J.S., Bokhimi, X., Hernandez, F., (2003) Langmuir, 19, p. 3583Wang, J.A., Bokhimi, X., Novaro, O., Lopez, T., Tzompantzi, F., Gomez, R., Navarrete, J., Salinas, E.L., (1999) J. Mol. Catal. A Chem., 137, p. 239Dumeignil, F., Sato, K., Imamura, M., Matsubayashi, N., Payen, E., Shimada, H., (2003) Appl. Catal. A Gen., 241, p. 319van Vliet, M.C.A., Mandelli, D., Arends, I.W.C.E., Schuchardt, U., Sheldon, R.A., (2001) Green Chem., 3, p. 243Silva, J.M.S., Vinhado, F.S., Mandelli, D., Schuchardt, U., Rinaldi, R., (2006) J. Mol. Catal. A Chem., 252, p. 186Mandelli, D., van Vliet, M.C.A., Sheldon, R.A., Schuchardt, U., (2001) Appl. Catal. A Gen., 219, p. 2001Arends, I.W.C.E., Sheldon, R.A., (2002) Top. Catal., 19, p. 133Cesquini, R.G., Silva, J.M.S., Woitiski, C.B., Mandelli, D., Rinaldi, R., Schuchardt, U., (2002) Adv. Synth. Catal., 344, p. 911Rinaldi, R., Schuchardt, U., (2005) J. Catal., 236, p. 335Rinaldi, R., Schuchardt, U., (2004) J. Catal., 227, p. 109Amenomiya, Y., Morikawa, Y., Pleizier, G., (1977) J. Catal., 46, p. 431Peri, J.B., (1975) J. Phys. Chem., 79, p. 1582Rinaldi, R., Sepulveda, J., Schuchardt, U., (2004) Adv. Synth. Catal., 346, p. 281Rebek, J., McCready, R., (1979) Tetrahedron Lett., 45, p. 4337Digne, M., Sautet, P., Raybaud, P., Euzen, P., Toulhoat, H., (2004) J. Catal., 226, p. 54Knözinger, H., Ratnasamy, P., (1978) Catal. Rev.-Sci. Eng., 17, p. 31Hiemstra, T., Vanriemsdijk, W.H., Bolt, G.H., (1989) J. Colloid Interface Sci., 133, p. 91Lefler, J.E., Miller, D.W., (1977) J. Am. Chem. Soc., 99, p. 480Duer, M.J., (2004) Introduction to Solid-State NMR Spectroscopy, , Blackwell Publishing, Oxford p. 235Nielsen, U.G., Skibsted, J., Jakobsen, H.J., (2001) Chem. Commun., p. 2690Walker, G.S., Pyke, D.R., Werrett, C.R., Williams, E., Bhattacharya, A.K., (1999) Appl. Surf. Sci., 147, p. 228Bhatia, S., Beltramini, J., Do, D.D., (1990) Catal. Today, 7, p. 309Tanabe, K., (1970) Solid Acids and Bases and Their Catalytic Properties, , Academic Press, New YorkTanabe, K., Misono, M., Ono, Y., Hattori, H., (1989) New Solid Acids and Bases and Their Catalytic Properties, , Elsevier, AmsterdamWang, J.A., Bokhimi, X., Morales, A., Novaro, O., López, T., Gómez, R., (1999) J. Phys. Chem. B, 103, p. 299Deubel, D.V., Frenking, G., Gisdakis, P., Herrmann, W.A., Rösch, N., Sundermeyer, J., (2004) Acc. Chem. Res., 37, p. 645Cotton, F.A., Wilkinson, G., Murillo, C., Bochmann, M., (1999) Advanced Inorganic Chemistry. sixth ed., , Wiley, New York p. 1303Vacque, V., Sombret, B., Huvenne, J.P., Legrand, P., Suc, S., (1997) Spectrochim. Acta Part A, 53, p. 55Landry, C.C., Pappe, N., Mason, M.R., Apblett, A.W., Tyler, A.N., MacInnes, A.N., Barron, A.R., (1995) J. Mater. Chem., 5, p. 331Kabalka, G.W., Pagni, R.M., (1997) Tetrahedron, 53, p. 7999Buffon, R., Schuchardt, U., (2003) J. Braz. Chem. Soc., 14, p. 34

Synthesis And Structural Characterization Of [ir4(co)8(η1-ph)(μ 4-η3-phpc(h)cph)(μ-pph2)], With A η1-phenyl Group Arising From Selective Cleavage Of A Coordinated Ph2pc(h)cph Ligand, And Of The Co-inserted Product [ir4(co)8(η1-c(o)ph)

The Ph2PC(H)CPh ligand in [Ir4(CO)9(μ3-η3-Ph 2PC(H)CPh)(μ-PPh2)] (1) undergoes selective P-C bond scission upon thermolysis in toluene at 70 °C, to give [Ir4(CO)8(η1-Ph)(μ 4-η3-PhPC-(H)CPh)(μ-PPh2)] (2; 60%), in addition to unreacted 1. 31P{1H}, 13C{1H}, and 1H NMR studies indicated the presence of two isomers in solution in a 3.2:1 ratio. The minor isomer 2b was fully characterized by single-crystal X-ray diffraction and exhibits a flat butterfly of metal atoms, with the PhPC(H)CPh ligand interacting with all four Ir atoms. The η1-Ph ligand is located on a wingtip Ir, on a radial site, trans to an Ir-Ir bond and cis to the P of the vinylidene ligand. A structure was proposed for the major isomer 2a, on the basis of multinuclear NMR spectroscopy, in which the η1-Ph ligand is located on an axial site, trans to the P of the vinylidene ligand. VT 31P{1H} NMR (25-90 °C) did not show interconversion of 2a and 2b. Carbonylation of the mixture of the two isomers yielded the CO inserted-products 3a and 3b (1:1.3), together with unreacted 2a. The molecular structure of [Ir4-(CO)8(η1-C(O)Ph)(μ 3-η3-PhPC(H)CPh)(μ-PPh2)] (isomer 3b), established by an X-ray analysis, is similar to that of 2b, except for the acyl group that remains bound to the same Ir atom but occupies the neighboring radial site. Multinuclear NMR studies showed that the η1-C(O)Ph group in isomer 3a occupies the same axial position as η1-Ph in 2a. A mechanism involving migration of the η1-Ph group in 2a and 2b, upon carbonylation, to give 3b and 3a, respectively, has been proposed.162248334838Garrou, P.E., (1995) Chem. Rev., 85, p. 171Deeming, A.J., Kimber, R.E., Underhill, M., (1973) J. Chem. Soc., Dalton Trans., p. 2589Brown, S.C., Evans, J., Smart, L.E., (1980) J. Chem. Soc., Chem. Commun., p. 1021Deeming, A.J., Kabir, S.E., Powell, N.I., Bates, P.A., Hursthouse, M.B., (1987) J. Chem. Soc., Dalton Trans., p. 1529Briard, P., Cabeza, X.A., Llamazares, A., Ouahab, L., Riera, V., (1993) Organometallics, 12, p. 1006. , and references thereinBergougnou, C., Bonnet, J.J., Fompeyrine, P., Lavigne, G., Lugan, N., Mansilla, F., (1986) Organometallics, 5, p. 60Deeming, A.J., Hardcastle, K.I., Kabir, S.E., (1988) J. Chem. Soc., Dalton Trans., p. 827Lugan, N., Bonnet, J.J., Ibers, J.A., (1988) Organometallics, 7, p. 1538Colbran, S.B., Irele, P.T., Johnson, B.F.G., Lahoz, F.J., Lewis, J., Raithby, P.R., (1989) J. Chem. Soc., Dalton Trans., p. 2023Sabo, S., Chaudret, B., Gervais, D., (1983) J. Organomet. Chem., 258, pp. C19Dubois, R.A., Garrou, P.E., (1986) Organometallics, 5, p. 466Blickensderfer, J.R., Kaesz, H.D., (1975) J. Am. Chem. Soc., 97, p. 2681Bonnet, J.J., Lavigne, G., Lugan, N., (1987) Inorg. Chem., 26, p. 585Deeming, A.J., Smith, M.B., (1993) J. Chem. Soc., Dalton Trans., p. 2041Benvenutti, M.H.A., Braga, D., Grepioni, F., Mann, B.E., Vargas, M.D., (1993) Organometallics, 12, p. 2955Vargas, M.D., Pereira, R.M.S., Braga, D., Grepioni, F., (1993) J. Chem. Soc., Chem. Commun., p. 1008Careni, M., Mori, G., Predieri, G., Rezende, N.S., Sappa, E., (1993) J. Chromatogr., 634, p. 143Farrugia, L.J., Rae, S.E., (1992) Organometallics, 11, p. 196Predieri, G., Tiripicchio, A., Vignali, C., Sappa, E., (1988) J. Organomet. Chem., 342, pp. C33Harding, M.M., Nicholls, B.S., Smith, A.K., (1983) J. Chem. Soc. Dalton Trans., p. 1479Carty, A.J., MacLaughlin, S.A., Nucciaroni, D., (1987) Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis, , Verkade, J. G., Quin, L. D., Eds.VCH: Deerfield Beach, FL, Chapter 16Regragui, R., Dixneuf, P.H., Taylor, N.J., Carty, A.J., (1986) Organometallics, 5, p. 1MacLaughlin, S.A., Carty, A.J., Taylor, N.J., (1982) Can. J. Chem., 60, p. 87Collman, J.P., Hegedus, L.S., Norton, J.R., Finke, R.G., (1987) Principles and Applications of Organotransition Metal Chemistry, , University Science Books: Mill Valley, CABassetti, M., Sunley, G.J., Fanizzi, F.P., Maitlis, P.M., (1990) J. Chem. Soc., Dalton Trans., p. 1799Monti, D., Frachey, G., Bassetti, M., Haynes, A., Sunley, G.J., Maitlis, P.M., Cantoni, A., Bocelli, G., (1995) Inorg. Chim. Acta, 240, p. 495Sheldrick, G.M., (1993) SHELX93, Program for Crystal Structure Determination, , University of Gottingen: Göttingen, GermanyWalker, N., Stuart, D., (1983) Acta Crystallogr., Sect. B, 39, p. 158Keller, E., SCHAKAL93, Graphical Representation of Molecular Models, , University of Freiburg, Freiburg, FR