Triorganoantimon- und Triorganobismutderivate von Carbonsäuren fünfgliedriger Heterocyclen Kristall- und Molekülstruktur von (C6H5)3Sb(O2C-2-C4H3S)2

Inhaltsübersicht. Triorganoantimon- und Triorganobismutdicarboxylate R₃M[O₂C(CH₂)ⁿ-2-C₄H₃X]₂ (M = Sb, R = CH₃, C₆H₁₁, C₆H₅, 4-CH₃OC₆H₄; M = Bi, R = C₆H₅, 4-CH₃C₆H₄; n = 0, X = O, S, NH, NCH₃. M = Sb, R = CH₃, C₆H₅; M = Bi, R = C₆H₅; n = 1, X = O, S. M = Sb, R = C₆H₁₁, n = 1, X = S; R = 4-FC₆H₄, n = 0, X = O, S, NCH₃; R = 2,4,6-(CH₃)₃C₆H₂, n = 0, X = O, S, NH) wurden durch Reaktionen von R₃Sb(OH)₂ (R = CH₃, C₆H₁₁, 2,4,6-(CH₃)₃C₆H₂), R₃SbO (R = C₆H₅, 4-CH₃OC₆H₄, 4-FC₆H₄) bzw. R₃BiCO₃ mit den entsprechenden fünfgliedrigen heterocyclischen Carbonsäuren 2-C₄H₃X(CH₂)_nCOOH dargestellt. Auf der Basis schwingungsspektroskopischer Daten wird für alle Verbindungen eine trigonal bipyramidale Umgebung vom M (zwei O-Atome von einzähnigen Carboxylatliganden in den apikalen, drei C-Atome von R in den äquatorialen Positionen) vorgeschlagen, ferner eine schwache Wechselwirkung zwischen O(=C) jeder Carboxylatgruppe und M. Die Kristallstrukturbestimmung von (C₆H₅)₃Sb(O₂C–2-C₄H₃S)₃ stützt diesen Vorschlag. Die Verbindung kristallisiert triklin [Raumgruppe P$1; a = 891,8(14), b = 1058,2(12), c = 1435,6(9) pm, α = 68,53(8), β = 85,47(9), γ = 85,99(11)°; Z = 2; d(ber.) = 1,607 Mg m^–3; V(Zelle) = 1255,6 ų; Strukturbestimmung anhand von 3947 unabhängigen Reflexen (F_o > 3σ(F²_o)), R(ungewichtet) = 0,037]. Sb bindet drei C₆H₅-Gruppen in der äquatorialen Ebene [mittlerer Abstand Sb–C: 211,1(5)pm] und zwei einzähnige Carboxylatliganden in den apikalen Positionen einer verzerrten trigonalen Bipyramide [mittlerer Abstand Sb–O: 212,0(4) pm]. Aus den relativ kurzen Sb – O(=C)-Abständen [274,4(4) und 294,9(4) pm] und aus der Aufweitung des dem O(=C)-Atom nächsten äquatorialen C–Sb–C-Winkels auf 145,9(2)° [andere C-Sb-C-Winkel: 104,4(2), 109,5(2)°] wird auf schwache Sb–O(=C)-Koordination geschlossen. Schließlich wird eine Korrelation zwischen dem (+, –)I-Effekt des Organoliganden R an M (M = Sb, Bi) und der Stärke der M–O(=C)-Koordination in den Dicarboxylaten R₃M[O₂C(CH₂)_n–2-C₄H₃X]₂ vorgeschlagen. Triorganoanümony and Triorganobismuth Derivatives of Carbonic Acids of Five-membered Heterocycles. Crystal and Molecular Structure of (C₆H₅)₃Sb(O₂C–2-C₄H₃S)₂ Triorganoantimony- and triorganobismuth dicarboxylates R₃M[O₂C(CH₂)_n–2-C₄H₃X]₂ (M = Sb, R = CH₃, C₆H₁₁, C₆H₅, 4-CH₃OC₆H₄; M = Bi, R = C₆H₅, 4-CH₃C₆H₄; n = 0, X = O, S, NH, NCH₃. M = Sb, R = CH₃, C₆H₅; M = Bi, R = C₆H₅; n = 1, X = O, S. M = Sb, R = C₆H₁₁, n = 1, X = S; R = 4-FC₆H₄, n = 0, X = O, S, NCH₃; R = 2,4,6-(CH₃)₃C₆H₂, n = 0, X = O, S, NH) have been prepared by reaction of R₃Sb(OH)₂ (R = CH₃, C₆H₁₁; 2,4,6-(CH₃)₃C₆H₂), R₃SbO (R = C₆H₅, 4-CH₃OC₆H₄, 4-FC₆H₄) or R₃BiCO₃ with the appropriate five-membered heterocyclic carboxylic acid. From vibrational data for all compounds a trigonal bipyramidal environment around M (two O atoms of unidendate carboxylate ligands in apical, three C atoms (of R) in equatorial positions) is proposed and also an additional weak interaction of O(=C) of each carboxylate group and M. The crystal structure determination of Ph₃Sb(O₂C–2-C₄H₃S)₂ gives additional prove to this proposal. It crystallizes triclinic [space group P$1; a = 891.8(14), b = 1058.2(12), c = 1435.6(9) pm, α = 68.53(8), β = 85.47(9), γ = 85.99(11)°; Z = 2; d(calc.) = 1.607 Mg m^–3; V_cell = 1255.6 ų; structure determination from 3 947 independent reflexions (F_o > 3σ(F²_o)), R(unweighted) = 0.037]. Sb is bonding to three C₆H₅ groups in the equatorial plane [mean distance Sb–C: 211.1(5) pm] and two unidentate carboxylate ligands in the apical positions of a distorted trigonal bipyramid [mean distance Sb–O: 212.0(4) pm]. From the relatively short Sb–O(=C) distances [274.4(4) and 294.9(4) pm] and from the enlarged value of the equatorial C–Sb–C angle next to the O(=C) atom [145.9(2)°; other C–Sb–C angles: 104.4(2), 109.5(2)°] additional weak Sb–O(=C) coordination is inferred. Finally a correlation between the (+, –) I-effect of the organic ligands It at M and the strength of the M–O = C interaction is suggested.     

Long-range fluorine-proton coupling in 1,2,4-triazole derivatives

Several 1,2,4-triazole derivatives containing a 2-fluorophenyl substituent at either the 3- or 5-position and a methyl group at the 4-position were synthesized. These derivatives exhibit long-range ¹⁹F-¹H and ¹⁹F-¹³C through-space coupling in their ¹H and ¹³C nmr spectra between the fluorine and the 4-methyl group. The close spatial proximity of these nuclei was confirmed by X-ray analysis and by fluorine irradiated proton observe ({¹⁹F}-¹H) NOE difference spectroscopy.     

Anab initio investigation of Cu2Se and Cu4Se2

Summary Experimentally known copper selenium clusters show extraordinary geometrical features, especially short Cu-Cu distances. We report the first theoretical investigation of Cu₂Se and Cu₄Se₂. Various quantum chemical methods (SCF, MP2, CPF, CCSD, CCSD(T), LDF) are applied to determine the importance of dynamic electron correlation. We find that inclusion of correlation does not essentially change the electronic structure of the clusters but has a strong influence on geometries. To reduce the computational effort we apply effective core potentials (ECPs) in combination with small, but carefully optimized basis sets. The applicability of simple modellings of correlation energies for approximate inclusion of correlation effects in SCF geometry optimizations is tested.     

Operational variables in high-performance liquid chromatography-electrospray ionization mass spectrometry of peptides and proteins using poly(styrene-divinylbenzene) monoliths

Capillary reversed-phase high-performance liquid chromatography (RP-HPLC) utilizing monolithic poly(styrene-divinylbenzene) columns was optimized for the coupling to electrospray ionization mass spectrometry (ESI-MS) by the application of various temperatures and mobile phase additives during peptide and protein analysis. Peak widths at half height improved significantly upon increasing the temperature and ranged from 2.0 to 5.4 s for peptide and protein separations at 70 degrees. Selectivity of peptide elution was significantly modulated by temperature, whereas the effect on proteins was only minor. A comparison of 0.10% formic acid (FA), 0.050% trifluoroacetic acid (TFA), and 0.050% heptafluorobutyric acid (HFBA) as mobile phase additives revealed that highest chromatographic efficiency but poorest mass spectrometric detectabilities were achieved with HFBA. Clusters of HFBA, water, and acetonitrile were observed in the mass spectra at m/z values >500. Although the signal-to-noise ratios for the individual peptides diverged considerably both in the selected ion chromatograms and extracted mass spectra, the average mass spectrometric detectabilities varied only by a factor of less than 1.7 measured with the different additives. Limits of detection for peptides with 500 nl sample volumes injected onto a 60 mm x 0.20 mm monolithic column were in the 0.2-13 fmol range. In the analysis of hydrophobic membrane proteins, HFBA enabled highest separation selectivity at the cost of lower mass spectral quality. The use of 0.050% TFA as mobile phase additive turned out to be the best compromise between chromatographic and mass spectrometric performance in the analysis of peptides and proteins by RP-HPLC-ESI-MS using monolithic separation columns.     

Stereoselective Syntheses of Tetrahydroesterastin-β -Lactam Analogues

A total synthesis of the optically active tetrahydroesterastin β -lactam analogue 2 using Miller's hydroxamate approach is described (Scheme 2). Significant modification of published procedures has resulted in a short and facile stereospecific preparation of the N-[(benzyloxycarbonyl)methyl]-β -lactam 17 starting from the readily available D -serine. This material served as intermediate for the preparation of a variety of N-[(benzyloxycarbonyl)methyl]tetrahydroesterastin β-lactam analogues (Scheme 5).     

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On semianalytic subsets of rigid analytic varieties

We show some topological properties of semianalytic subsets of rigid analytic varieties: curve selection lemma, the closure of a semianalytic subsetS is semianalytic, for every quasi-compact morphismf. As an application we show that a morphismf: X Y of rigid analytic varieties is open at a pointx X if and only if SpecO _X,x SpecO _Y,f(x) is surjective.