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53. Determination of the absolute configuration of (-)-(2R)-succinic-2-d acid by neutron diffraction study: unambiguous proof of the absolute stereochemistry of the NAD+/NADH interconversion.

Author

Yuan, H S, Stevens, R C, Fujita, S, Watkins, M I, Koetzle, T F, and Bau, R

Abstract

The absolute configuration of the CHD group (D = deuterium) in (-)-(2R)-succinic-2-d acid, as prepared from (-)-(2S,3R)-malic-3-d acid, has been shown unambiguously to be R by the technique of single-crystal neutron diffraction. The optically active cation (+)-phenylethylammonium was used as the chiral reference. The structure of [C6H5CH3CHNH3]+[HOOCCH2CHDCOO]- has been studied with x-ray diffraction at room temperature and neutron diffraction at 100 K. Crystal data from the neutron diffraction analysis of the phenylethylammonium salt of the title compound at 100 K: space group P21; a = 8.407(2) A, b = 8.300(4) A, c = 8.614(2) A, beta = 91.20(3) degrees; unit cell volume = 600.9(3) A3, zeta = 2 (numbers in parentheses are the estimated standard deviations). Final agreement factors are R(F2) = 0.0355 and R(wF2) = 0.0457 for 1690 independent neutron reflections and 297 parameters varied. The result confirms the stereochemistry of the malate/succinate transformation, as well as the NAD+/NADH interconversion, and demonstrates the usefulness of the single-crystal neutron diffraction method for determining the absolute configuration of molecules having a chiral monodeuteriomethylene group.

Published
1988
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55. Preparations of (1,4,7-Trimethyl-1,4,7-triazacyclononane)RhMe<INF>3</INF>, Some of Its Rh−C Acid-Cleavage Derivatives, and (1,4,7-Trineohexyl-1,4,7-triazacyclononane)RhMe<INF>3</INF>

Author

Wang, L., Wang, C., Bau, R., and Flood, T. C.

Abstract

The series of Cn-coordinated organorhodium complexes CnRhMe3-nXn and NhCnRhMe3 have been synthesized and characterized (n = 1−3; Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane; NhCn = 1,4,7-trineohexyl-1,4,7-triazacyclononane; X = Cl-, Br-, OTf-, BF4-). X-ray diffraction data on CnRhMe3 (1) and NhCnRhMe3 show the expected facial coordination of Cn. The Rh−N lengths show a large trans influence from the strong-field methyl groups. The 1H NMR chemical shifts of the rhodium methyls show a good correlation with the degree of substitution (n) of electron-withdrawing substituents on Rh. CnRhMe3-nXn (n = 1, 2) have well-defined solvent coordination properties when X = OTf- and BF4-. The coordinating ability of the anions for this CnRh system follows the trend BF4- &lt; OTf- ≪ Br- &lt; Cl-. The relative coordinating ability of solvents for these complexes is CH2Cl2 ≪ MeOH &lt; DMSO &lt; H2O. CnRhMe2(OTf) and CnRhMe(OTf)2 react with CO to form [CnRhMe2(CO)]OTf and (in THF) [CnRhMe(CO)(THF)](OTf)2, respectively, which do not undergo CO insertion into the Rh−CH3 bond under 1 atm of CO even at 80 °C. The ligands BzCn, NhCn, and NpCn were prepared to explore the enhancement of solubility of RCnRh complexes in less polar, weakly coordinating solvents, with the result that NhRhMe3 demonstrates better solubility and BzCnRhMe3 poorer solubility than CnRhMe3 in solvents such as toluene. NpCnRhCl3 was not successfully prepared.

Published
1996

56. Preparation, Characterization, and X-ray Structure of the 1:1 Complex of o-Acetylstyrene and Carbonylbis(triphenylphosphine)ruthenium. A New Catalyst for the Copolymerization of Acetophenone and 1,3-Divinyltetramethyldisiloxane

Author

Lu, P., Paulasaari, J., Jin, K., Bau, R., and Weber, W. P.

Abstract

Treatment of dihydridocarbonyltris(triphenylphosphine)ruthenium with a stoichiometric amount of styrene, followed by addition of o-acetylstyrene leads to a 1:1 complex of o-acetylstyrene and carbonylbis(triphenylphosphine)ruthenium. This species has been fully characterized and its structure determined by X-ray crystallography. This 1:1 complex is able to catalyze the copolymerization of acetophenone and 1,3-divinyltetramethyldisiloxane.

Published
1998

60. Spectroscopic studies and x-ray crystal structure determination of the complex cis-(S-ethylcysteine)platinum(II)dichloride

Author

Theodorou, V. Photaki, I. Hadjiliadis, N. Gellert, R.W. Bau, R.

Abstract

IR, 1H NMR and 13C NMR spectra of cis-Pt(S-EtCys)Cl2 have been analyzed and interpreted in favor of a structure which the ethyl-cysteine ligand coordinates through its S and N atoms. Additionally, the 1H and 13C NMR spectra show the existence of two diastereomers, differing in their absolute configuration at sulfur. These conclusions were confirmed by a single-crystal X-ray structure determination, which showed the presence of both diastereomers in the unit cell. Crystallographic details: cis-Pt(S-EtCys)Cl2 crystallizes in the monoclinic space group P21, with a = 8.336(6) Å, b = 10.997(8) Å, c = 15.097(9) Å, β = 120.76(3)°, Z = 4. FinalR factor = 0.054 for 1842 reflections. © 1982.

Published
1982

62. The crystal structure of tetrahydrothiamine and its Co(II) complex

Author

Bau, R. Hyun, Y.-S. Lim, J. Choi, H.-K. Yannopoulos, A. Hadjiliadis, N.

Abstract

The structures of tetrahydrothiamine and its Co(II) complex have been by X-ray crystallography. The parent ligand crystallizes in the monoclinic space group P21 c with two independent molecules in the unit cell. The most notable feature of the structure of the title compound is the fact that the tetra hydrothiazolidine ring is, as expected, distinctly non-planar in contrast to its unsaturated analog thiazolidine, which has a planar (NCSCC) ring. The two substituents of the tetrahydrothiazolidine ring, -CH3 and -CH2CH2OH, adopt a syn conformation in both independent molecules of the unit cell. The final R factor obtained was 6.3% for 2124 reflections. The Co(II) complex was prepared by reacting equivalent amounts of the ligand and CoCl2 in CHCl3. The complex crystallizes from hot methanol as its tetrahydrothiaminium salt. [Tetrahydrothiaminium]+- [CoCl3tetrahydrothiamine]- forms triclinic crystals (space group P1), and its structure was refined to a final R factor of 4.8% for 2568 reflections. The cobalt atom is tetrahedrally coordinated by three chloride ions and the parent ligand. The most significant feature of the structure of this complex is the fact that cobalt binds to the N1′ site of the pyrimidine ring, which is consistent with earlier suggestions that this atom acts as the metal-binding site in enzymatic reactions invloving thiamine as a cofactor. © 1988.

Published
1988

63. Complexes of mercury(II) with thiamine

Author

Hadjiliadis, N. Yannopoulos, A. Bau, R.

Abstract

The reaction of mercuric chloride with thiamine has been explored. Two distinct salts, [ThH]2+[HgCl3]-2 and [ThH]2+ [HgCl42- (Th = thiaminium = protonated thiamine), were isolated at pH 3.5. The structure of the latter compound was solved with X-ray methods and shows the presence of discrete thiaminium and tetrachloromercurate ions. At a higher pH (5.5), a third compound, not yet fully characterized, was isolated having the empirical formula (Hg2Cl5(Th). Crystals details on [ThH]2+ [HgCl4]2-·H2O: space group P21/c (monoclinic); a = 17.189(17) Å, b = 8.817(5) Å, c = 13.971(6) Å, β = 106.21(6)°, V = 2033(2) Å3, Z = 4. Final R factor = 7.3% for 2013 reflections. © 1983.

Published
1983

64. Complexes of Tetrahydrothiamine and its Phosphate Esters With Chromium(III), Iron(III), Cobalt(II), Nickel(II) and Copper(II)

Author

Hadjiliadis, N. Yannopoulos, A. De Grave, E. Bau, R.

Abstract

The reactions of tetrahydrothiamine (thth) and its mono‐(ththmp) and pyro‐(ththpp) phosphate esters, with metal halides of NiII, CuII, CoII, CrIII and FeIII were studied in organic solvents. Complexes of the formulae NiL(H2O)4Cl2, CuL(H2O)Cl2, CoL(H2O)3Cl2, CrL(H2O)2Cl3 and FeL(H2O)3Cl3, with L thth, ththmp and ththpp, were isolated as solid adducts. An attempt was made for their characterization, with elemental analysis, conductivity and magnetic susceptibility measurements, ir, uv‐vis and Mössbauer spectra in the case of the FeIII complexes. The N atom of the pyrimidine moiety of the ligands is proposed as a possible coordination site, in the case of NiII, CuII and CoII complexes. Copyright © 1989 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim

Published
1989

65. Effektiv utredning och rapportering

Author

Bau, R., Nilsson, Anders G., Westelius, A., Bau, R., Nilsson, Anders G., and Westelius, A.

Abstract

Föreliggande rapport innehåller råd, verktyg och dokumentationsstöd vid författande av akademiska rapporter och uppsatser inom främst ämnesområdena företagsekonomi och information management(informatik). Rapporten har använts under ett antal år inom grundutbildningen för blivande civilekonomer vid Handelshögskolan i Stockholm (HHS)

Published
1989

66. Neutron and X-ray Diffraction Studies and DFT Calculations of Asymmetric Bis(silyl) Niobocene Hydrides

Author

Dorogov, K. Y., Dumont, E., Ho, N.-N., Churakov, A. V., Kuzmina, L. G., Poblet, J.-M., Schultz, A. J., Howard, J. A. K., Bau, R., Lledos, A., and Nikonov, G. I.

Abstract

The first asymmetric bis(silyl) niobocene hydrides Cp2Nb(SiHMe2)H(SiXMe2) (2:  X = F (a), Cl (b), Br (c), I (d)), having interligand interactions Nb−H···Si−X, were prepared by selective halogenation of the Si−H bond in Cp2Nb(SiHMe2)2H. X-ray studies of 2b,c and a combined X-ray/neutron diffraction study of 2b establish a slightly stronger interaction of the niobium-bound hydride with the halosilyl ligand.

Published
2004

72. ChemInform Abstract: Aluminum Dichloride and Dibromide. Preparation, Spectroscopic (Including Matrix Isolation) Study, Reactions, and Role (Together with Alkyl(aryl)aluminum Monohalides) in the Preparation of Organoaluminum Compounds.

Author

OLAH, G. A., primary, FAROOQ, O., additional, FARNIA, S. M. F., additional, BRUCE, M. R., additional, CLOUET, F. L., additional, MORTON, P. R., additional, PRAKASH, G. K. S., additional, STEVENS, R. C., additional, BAU, R., additional, LAMMERTSMA, K., additional, SUZER, S., additional, and ANDREWS, L., additional

Published
1988
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76. ChemInform Abstract: NEUTRON AND X-RAY DIFFRACTION STUDIES OF TRIS(METHYLDIPHENYLPHOSPHINE)(TETRAHYDROBORATO(1-))COPPER, CU(P(C6H5)2CH3)3(BH4). THE FIRST ACCURATE CHARACTERIZATION OF AN UNSUPPORTED METAL-HYDROGEN-BORON BRIDGE BOND

Author

TAKUSAGAWA, F., primary, FUMAGALLI, A., additional, KOETZLE, T. F., additional, SHORE, S. G., additional, SCHMITKONS, T., additional, FRATINI, A. V., additional, MORSE, K. W., additional, WEI, C.-Y., additional, and BAU, R., additional

Published
1981
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