Showing papers by "Bernt Krebs published in 1997"
226 citations
TL;DR: A series of dinuclear copper(II) complexes as models for the type 3 copper protein catechol oxidase were synthesized as mentioned in this paper, which were characterised by spectroscopic, electrochemical, and in some cases, by single-crystal X-ray diffraction studies.
Abstract: A series of dinuclear copper(II) complexes as models for the type 3 copper protein catechol oxidase were synthesised. They were characterised by spectroscopic, electrochemical, and in some cases, by single-crystal X-ray diffraction studies: [Cu2(L1)(OH)(EtOH)(H2O)][ClO4]2·H2O 1, [Cu2(L2)(OH)][NO3]22, [Cu2(L3)(OMe)(MeOH)(ClO4)]ClO43, [Cu2(L4)(OH)(MeOH)2][BF4]24, [Cu2(L5)(OMe)][ClO4]2·2MeOH 5, [Cu2(L6)(OMe)(MeOH)(ClO4)]ClO46 and [Cu2(L7)(OMe)(MeOH)(ClO4)]ClO47 (HL1 = 4-bromo-2,6-bis(4-methylpiperazin-1-ylmethyl)phenol, HL2 = 4-bromo-2,6-bis[(2-pyridylmethyl)aminomethyl]phenol, HL3 = 4-bromo-2,6-bis{[2-(2-pyridyl)ethyl]aminomethyl}phenol, HL4 = 4-bromo-2,6-bis{[2-(1-methyl-2-imidazolyl)ethyl]aminomethyl}phenol, HL5 = 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[(2-pyridylmethyl)aminomethyl]phenol, HL6 = 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-{[2-(2-pyridyl)ethyl]aminomethyl}phenol and HL7 = 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-{[2-(1-methyl-2-imidazolyl)ethyl]aminomethyl}phenol). The copper centres are µ-phenoxo bridged by the pentadentate dinucleating ligand and exogenously µ-hydroxo or µ-methanolato bridged. Complex 1 crystallises in P21/c with a = 16.913(3), b = 11.046(2), c = 16.617(3) A, β = 94.06(3)°, U = 3097 A3 and Z = 4. Complex 3 crystallises in P21/n with a = 10.592(2), b = 12.123(2), c = 24.482(5) A, β = 92.97(3)°, U = 3139 A3 and Z = 4. Complex 4 crystallises in Pbcn with a = 16.043(3), b = 12.689(3), c = 15.810(3) A, U = 3218 A3 and Z = 4. Complex 6 crystallises in P21/c with a = 17.889(4), b = 10.401(2), c = 16.269(4) A, β = 92.94(2)°, U = 3023 A3 and Z = 4. Complex 7 crystallises in P21/c with a = 17.349(3), b = 8.828(2), c = 19.797(4) A, β = 94.04(3)°, U = 3025 A3 and Z = 4. A catecholase activity study revealed that only complexes 1, 5, 6 and 7 have significant catalytic activity with respect to the aerial oxidation of 3,5-di-tert-butylcatechol. A kinetic treatment on the basis of the Michaelis–Menten model was applied.
210 citations
TL;DR: In this paper, the system consisting of an iron(III) salt and β(2pyridyl)-methylamine (bpia) was shown to react with various catechols with insertion of dioxygen.
52 citations
TL;DR: The new polymeric compounds (Me4N)2Na2[Na2Co2H2W12O42(H2O)12]·16H 2O (1) and Na3[NaCo3H 2W 12O42-(H2 O)16]·22H 2 O (2) have been synthesized by reaction of sodium tungstate, and cobalt(II) nitrate as mentioned in this paper.
50 citations
TL;DR: In this paper, the preparation and characterization of mononuclear silver(I) nitrate complexes with various heterocyclic thiones (pytH = pyridine-2-thione, pymtH=pyridine 2-thiones, quin2TH = quinoline-2thione and izdtH = thiazolidine-2 -thione), mbzimtH2 = N=methyl-benzimidazoline- 2thione as ligands are described.
44 citations
21 citations
TL;DR: In this article, anionen bestehen aus zwei kantenverknupften verzerrten SeBr6-Oktaedern and sind uber Cl Wechselwirkungen zu einem zweidimensionalen Netzwerk verknupft.
Abstract: Aus einer gesattigten Losung von SeCl4 in 98% igem Ethanol konnten durch Zugabe von Morpholin blasgelbe Kristalle der Verbindung [C4H10NO]2[SeOCl4] (1) gewonnen werden (Raumgruppe Pnma, a = 7.731(5) A, b = 21.053(16) A, c = 9.725(8) A bei 150 K). In 1 liegt ein Teilhydrolyseprodukt der Chloroselenate(IV), das quadratisch pyramidale [SeOCl4]2−-Anion, als Morpholiniumsulzvor. Die Anionen sind uber schwache Se… Cl-Wechselwirkungen zu Ketten verknupft. Die Morpholinium-Kationen bilden Wasserstoffbruckenbindungen zu Cl-Atomen der Anionen aus.
[C4H10NO]2[Se2Br10] (2) kann aus einer gesattigten Losung von SeBr4 in 47% iger wasriger Bromwasserstoffsaure durch Zugabe von Morpholin in Form roter Kristalle erhalten werden (Raumgruppe P21/c, a = 8.357(2) A, b = 17.656(6) A, c = 8.495(2) A, β = 95.49(2)° bei 150 K). Die [Se2Br10]2 -Anionen bestehen aus zwei kantenverknupften verzerrten SeBr6-Oktaedern. Intermolekulare Anion-Anion-Wechselwirkungen verknupfen die Anionen zu einem zweidimensionalen Netzwerk.
[(CH3)2CHC(NH2)(OH)][Te3Cl13] · (CH3)2CHCN (3) wurde aus einer Losung von TeCl4 in iso-Butyronitril/konz. HCl dargestellt (Raumgruppe P1, a = 8.718(2) A, b = 11.030(2) A, c = 15.756(4) A, α = 84.49(2)°, β = 79.24(2)°, γ = 86.10(2)° bei 170 K). Die [Te3Cl13]−-Anionen bestehen aus drei cis-kanten-verknupften verzerrten Oktaedern und sind uber Cl … Cl Wechselwirkungen zu einem zweidimensionalen Netzwerk verknupft. Als Kationen treten protonierte Isobuttersaure-amid-Molekule auf. 1, 2 und 3 wurden durch vollstandige Rontgenstrukturanalysen charakterisiert. Uber Raman-spektroskopische Untersuchungen an 1 und 2 wird berichtet.
Stabilization of Oxohalogeno and Halogenochalcogenates(IV) by Proton Acceptors - Synthesis, Structures and Properties of [C4H10NO]2[SeOCl4], [C4H10NO]2[Se2Br10] and [(CH3)2CHC(NH2)(OH)][Te3Cl13] · (CH3)2CHCN
Pale yellow crystals of the compound [C4H10NO]2[SeOCl4] (1) were isolated by adding morpholine to a saturated solution of SeCl4 in 98% ethanol (space group Pnma, a = 7.731(5) A, b = 21.053(16) A, c = 9.725(8) A at 150 K). The square pyramidal [SeOCl4]2 anion in this morpholinium salt is a partial hydrolysis product of chloroselenates(IV). The anions are connected to chains by weak Se … Cl interactions. The morpholinium cations form hydrogen bonds to Cl atoms of the anions.
The red compound [C4H10NO]2[Se2Br10] (2) was synthesised by adding morpholine to a saturated solution of SeBr4 in 47% hydrobromic acid (space group P21/c, a = 8.357(2) A, b = 17.656(6) A, c = 8.495(2) A, β = 95.49(2)° at 150 K). The [Se2Br10]2− anions consist of two edge sharing distorted octahedra. Intermolecular interactions connect the anions to a two-dimensional network.
[(CH3)2CHC(NH2)(OH)][Te3Cl13]·(CH3)2CHCN (3) was isolated from a solution of TeCl4 in iso-butyronitrile/conc. HCl (space group P1, a = 8.718(2) A, b = 11.030(2) A, c = 15.756(4) A, α = 84.49(2)°, β = 79.24(2)°, γ = 86.10(2)° at 170 K). The [Te3Cl13]− anions consist of three distorted cis-edge sharing octahedra. A two-dimensional anionic network is formed by Cl…Cl interactions. The cation is a protonated iso-butyric amide. 1, 2 and 3 were characterized by single-crystal X-ray structure analyses. Raman spectra of 1 and 2 are reported.
16 citations
15 citations
TL;DR: In this article, the FeCl3-catalyzed hydrolytic polycondensation of suited trichlorosilanes in a biphasic system was studied, which yields e.g. the new octa(silasesquioxane) (BrCH2CH2 CH2CH 2CH2)8Si8O12.
Abstract: Ein Verfahren zur FeCl3-katalysierten Hydrolyse von Trichlorsilanen im Zweiphasensystem wird untersucht und das dargestellte, neue Silasesquioxan (BrCH2CH2CH2)8Si8O12 isoliert und charakterisiert.
Synthesis and Structures of γ-Halopropyl-octa(silasesquioxanes)
As a more rapid and versatile synthetic approach, we have studied the FeCl3-catalyzed hydrolytic polycondensation of suited trichlorosilanes in a biphasic system which yields e.g. the new octa(silasesquioxane) (BrCH2CH2CH2)8Si8O12.
15 citations
TL;DR: In this paper, the selenoamide is prepared by cycloaddition and stereospecific electrocyclic ring-opening, yielding, with respect to the resulting CC double bond, the E isomer as the only product.
Abstract: Bis(trifluoromethylketiminoalkyl)diselanes [SeC(=NR)CF3]2 (6) [R = Me (a), iPr (b), tBu (c)] have been prepared in high yields (55-70%) by reaction of the diselane (SeC2F5)2 (2) with RNH2. However, the analogous reaction of 2 with secondary amines, R2NH, results in the cleavage of the Se-Se bond and leads to the N,N-dialkyl-2,2,2-trifluoroselenoacetamides Se=C(NR2)CF3 (7) [R = Me (a), iPr (b)]. Cleavage of 6a-6c with Me3SnH affords the selenoamides Se=C(NHR)CF3 (9) and the corresponding stannylselanes Me3SnSeC(=NR)CF3 (10) [R = Me(a), iPr (b), tBu (c)]. Selenoamides 7 and 9 can also be prepared from pentafluoroethylselenol HSeC2F5 (3), Se=C(F)CF3, (1) or its polymer [SeC(F)CF3]n (4) and primary or secondary amines. N,N-dialkyl-2-methyl-3-fluoro-4,4,4-trifluoroselenoacrylamides Se=C(NR2)C(Me)=C(F)CF3[R = Et (13a), iPr (13b)] are prepared in moderate yields under mild conditions by treating either trifluoromethylselenocarbonyl fluoride (1) or its polymer [SeC(F)CF3]n with 1-dialkylamino-1-propynes. The reaction proceeds by [2 + 2] cycloaddition and stereospecific electrocyclic ring-opening, yielding, with respect to the resulting CC double bond, the E isomer as the only product. The molecular structures of 7b, 9a and 13b show the typical features of selenoamides with C(Se)-N bond shortening and C-Se bond elongation due to π interaction of the N lone pair with the CSe double bond. The observed perpendicular orientation of the selenoamide and the alkene units of 13b prevents π delocalization.
12 citations
TL;DR: The crystal structure of β-Ab2Te3 has been determined by means of single crystal x-ray diffractometry as discussed by the authors, and the examined crystal can be described as a pseudomerohedric twin with a plane of reflection in (001) as twin element.
Abstract: Die Kristallstruktur von β-Al2Te3 konnte auf der Grundlage von Einkristalldaten ermittelt werden. Der vermessene Kristall lag als pseudomeroedrischer Reflektionszwilling nach (001) vor. Die Verfeinerung in P21/c (Nr. 14) mit a - 7,181(1) A, b = 12,848(3) A, c = 14,167(3) A, β = 90,04(2)°, V = 1307,1 A3 und Z = 8 konvergierte gegen einen konventionellen R-Wert von 0,0245. β-Al2Te3 kristallisiert in einer Schichtstruktur und stellt einen neuartigen Strukturtyp dar.
Crystal Structure of β-Al2Te3
The crystal structure of β-Ab2Te3 has been determined by means of single crystal x-ray diffractometry. The examined crystal can be described as a pseudomerohedric twin with a plane of reflection in (001) as twin element. The refinement in P21/c (No. 14) with the crystal parameters a = 7.181(1) A, b = 12.848(3) A. c = 14.167(3) A, β = 90.04(2)°, V = 1307.1 A3 and Z = 8 resulted in a final R-value (based on F) of 0.0245. β-Al2Te3 crystallizes in a layered arrangement and represents a new structure type.
TL;DR: The UO3S4 core deformation from ideal geometry varies widely in the solid state and is shown to become stereochemically rigid at moderately low temperature in solution as mentioned in this paper.
TL;DR: In this paper, the reaction of [M(po)(H 2 O) 2 ] 2+ (MPt or Pd; po = 2-(py3idin-2-yl)-2-oxazoline) with the model nucleobases 1-methylthymine (1-MeT) and 1 -methyluracil (1 -MeU) were studied.
TL;DR: A comprehensive overview on the structural diversity of thio- and selenoborates is given with special focus to the molecular features of boron-selenium chemical in binary and ternary compounds in this paper.
Abstract: A comprehensive overview on the structural diversity of thio- and selenoborates is given with special focus to the molecular features of boron-selenium chemical in binary and ternary compounds.
TL;DR: In this article, a general assignment of their vibrational (IR and Raman) spectra, compatible with the structural characteristics, is proposed, and the thermal behavior of both complexes is investigated by means of TG and DTA methods.
Abstract: Die Kristallstrukturen von [Co(Urocan)2(H2O)4] und [Zn(Urocan)2(H2O)4] (Urocan = Anion der Imidazol-4-acrylsaure = Urocaninsaure) wurden rontgenographisch an Einkristallen bestimmt. Sie sind isostrukturell und kristallisieren in der monoklinen Raumgruppe P21/c mit Z = 2. Eine Zuordnung ihrer Schwingungsspektren (IR und Raman), die mit den strukturellen Eigenschaften im Einklang steht, wird vorgeschlagen. Das thermische Verhalten beider Komplexe wurde an Hand von TG- und DTA-Messungen untersucht.
Crystal Structure, Vibrational Spectra, and Thermal Behavior of the Cobalt(II) and Zinc(II) Complexes of Urocanic Acid
The crystal structures of [Co(Urocan)2(H2O)4] and [Zn(Urocan)2(H2O)4] (urocan = anion of 4-imidazoleacrylic acid = urocanic acid) have been solved by single-crystal X-ray diffractometry. They are isostructural and crystallize in the monoclinic space group P21/c with Z = 2. A general assignment of their vibrational (IR and Raman) spectra, compatible with the structural characteristics, is proposed. The thermal behavior of both complexes was investigated by means of TG and DTA methods.
TL;DR: In this paper, the crystal and molecular structures of the title compounds have been determined by x-ray structure analysis, and the compounds (I and II) crystallize in space groups P212121 and 12/a respectively.
Abstract: The crystal and molecular structures of the title compounds have been determined by x-ray structure analysis. The compounds (I) and (II) crystallize in space groups P212121 and 12/a respectively. The structures were solved by direct methods and refined to R = 0.058 and R = 0.046. The saturated pyrimidine-2-one ring in both structures deviates from the planarity. There are two intermolecular hydrogen bonds in (I) and (II).
The configuration at C4 in (I) is S.