Christine Kunze

Technische Universität Braunschweig, Brunswyck, Lower Saxony, Germany

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Publications (7)16.95 Total impact

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    ABSTRACT: The synthesis of calix[4]arene-based phosphorus diamides and phosphites is described. These oligocyclic ligands have been tested in the Rh(I)- catalyzed hydroformylation of 1-octene. Depending on the reaction conditions, yields up to 99% and n/iso-selectivities between 0.7 and 2.6 have been observed. tert-Butyl groups on the upper rim of the calix[4]arene template had a beneficial effect on the catalytic reaction. In general biuret-derived P-ligands were superior. For comparison, the corresponding “monomeric” ligands have also been synthesized and were employed in the catalytic reaction. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:577–585, 2001
    No preview · Article · Mar 2010 · Heteroatom Chemistry
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    ABSTRACT: The mol­ecule of the title compound, C11H6ClO3P, is essentially planar, except for the P, Cl and carbonyl O atoms. Bond lengths at phospho­rus are P—O = 1.6110 (18) and 1.6290 (18) Å, and P—Cl = 2.0890 (9) Å. The mol­ecules are linked to form ribbons parallel to the b axis by two C—H⋯O and one P⋯O interaction.
    No preview · Article · Dec 2002 · Acta Crystallographica Section E Structure Reports Online
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    ABSTRACT: The mol­ecule of the title compound, C11H6ClO3P, is essentially planar, except for the P and Cl atoms. Bond lengths at phospho­rus are P—O = 1.6141 (8) and 1.6143 (9), and P—Cl = 2.0958 (4) Å. The mol­ecules are linked to form double ribbons parallel to the b axis by one C—H⋯O and one C—H⋯Cl interaction.
    No preview · Article · Dec 2002 · Acta Crystallographica Section E Structure Reports Online
  • S.A. Katsyuba · R. Schmutzler · U. Hohm · C. Kunze
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    ABSTRACT: The conformations and vibrational spectra of the 2,6-dimethylanisole and n-propyl-2,6-dimethylphenyl ether molecules have been analysed within the framework of density functional theory. The calculated force field (B3LYP/6-31G∗) has been transformed to internal coordinates, and the set of 10 different scaling factors has been applied. The scaled quantum mechanical method reproduces the experimental range of the IR and Raman spectra with high accuracy. According to the computations, the conformational behaviour of the alkyl aryl ethers studied is similar to the related dialkyl ether molecules, i.e. the CO–CC bond prefers the anti conformation, while the OC–CC bond prefers the gauche conformation. The major part of the vibrational spectra of the title compounds can be approximated by the sum of the vibrational modes of their constituent groups, these modes being transferable among the related molecules.
    No preview · Article · Jun 2002 · Journal of Molecular Structure
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    ABSTRACT: New calix[4]arene-based bis-phosphonites, bis-phosphites and bis-O-acylphosphites were synthesized and characterized. Treatment of these P-ligands with selected rhodium and platinum precursors led to mononuclear complexes that were satisfactorily characterized. The solid state structure of the dirhodium(I) complex 14 has been determined by X-ray diffraction. The two rhodium centres are bridged by two chloro ligands; one rhodium atom is further coordinated by calix[4]arene phosphorus atoms and the other by cyclooctadiene. The new calix[4]arene P-ligands were tested in the Rh(I) catalyzed hydroformylation of 1-octene. All Rh(I) complexes catalyzed the reaction leading to high chemoselectivity with regard to the formation of aldehydes. Yields and n/isoselectivities depended on the reaction conditions. Average yields of 80% and n/iso-ratios of about 1.3 to 1.5 were observed. High yields of aldehydes can be achieved using the methoxy substituted P-ligands at low Rh:ligand ratios.
    No preview · Article · May 2002 · Zeitschrift für anorganische Chemie
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    ABSTRACT: The reaction behaviour of 1, 3, 5-triaza-2σ3λ3-phosphorin-4, 6-dionyloxy-substituted calix[4]arenes towards mono- and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)-substituted calix[4]arene (4) and its tert-butyl-derivative (1) with [(cod)RhCl]2 yielded the mono- and disubstituted binuclear rhodium complexes 2, 3, and 5. In all cases, a C2-symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3-alternating conformation. The X-ray crystal structure determination of 5 confirmed [(calixarene)RhCl]2-coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh2Cl2 core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)-bis(methoxy)-substituted tert-butyl-calix-[4]arene (7) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF4 led to the expected cationic monorhodium complexes 5 and 8, involving 1, 3-alternating P-Rh-P-coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the 1J(PRh) coupling constants in the 31P-NMR-spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF4, to the corresponding mononuclear cationic complexes 9 and 10. Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta-1, 5-diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy.Reaction of 4 with (cod)PtCl2 led to the PtCl2-complex (11). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ31P and characteristic values of 1J(PPt)). NMR-spectroscopic evidence was found for the existence of the cone conformation in the cis-configuration of 11.Ein- und zweikernige Komplexe des Rhodiums und Platins von 1, 3, 5-Trimethyl-1, 3, 5-triaza-2σ3λ3-phosphorin-4, 6-dionyloxy-substituierten Calix[4]arenenDas Reaktionsverhalten von 1, 3, 5-Trimethyl-1, 3, 5-triaza-2σ3λ3-phosphorin-4, 6-dionyloxy-substituierten Calix-[4]arenen gegenüber ein- und zweikernigen Rhodium- und Platin-Komplexen wurde untersucht. Besonderes Augenmerk wurde auf die Untersuchung der Struktur und des dynamischen Verhaltens der Produkte im festen Zustand und in Lösung gelegt. Abhängig vom molaren Verhältnis der Reaktanden lieferte die Umsetzung des tetrakis(triazaphosphorindionyloxy)-substituierten Calix[4]-arens (4) und seines tert-Butyl-Analogons (1) mit [(cod)RhCl]2 die mono- und disubstituierten, zweikernigen Rhodiumkomplexe 2, 3 und 5. In allen Fällen wurde eine C2-symmetrische Struktur in Lösung nachgewiesen, die anscheinend aus einem schnellen intramo-lekularen Austauschprozeß zwischen der Konus- und der 1, 3-alternierenden Konformation resultiert. Die Röntgenstrukturanalyse von 5 bestätigte die [(Calixaren)RhCl]2-Koordination über zwei gegenüberliegende Phosphoratome mit einem P ⃜P-Abstand von 345 pm. Der Komplex zeigt kristallographische Inversionssymmetrie, damit ist die Rh2Cl2-Verbrückungseinheit exakt planar. Die Reaktion von 1 und dem bis(triazaphosphorindionyloxy)-bis(methoxy)-substituierten tert-Butyl-Calix[4]aren (7) mit (cod)-Rh(acac) in äquimolarem Verhältnis und anschließender Umsetzung mit HBF4 führte zu den erwarteten Monorhodiumkomplexen 6 und 8 mit 1, 3-alternierender P-Rh-P-Koordination. Die Konus-Konformation wurde in Lösung durch NMR-Spektroskopie und charakteristische 1J(PRh)-Kopplungskonstanten in den 31P-NMR-Spektren nachgewiesen. Die Umsetzung äquimolarer Mengen von 4 mit (cod)Rh(acac) und (nbd)Rh(acac) führte durch Substitution des schwachkoordinierten Acetylacetonato-Restes und nach Zugabe von HBF4 zu den entsprechenden einkernigen Komplexen 9 und 10. Nur zwei der vier Phosphoratome von 9 und 10 sind ans Zentralmetallatom koordiniert. Abspaltung von Cycloocta-1, 5-dien oder Norbornadien wurde nicht beobachtet. Für beide Verbindungen wurde die Konus-Konformation durch NMR-Spektroskopie nachgewiesen. Die Umsetzung von 4 mit (cod)PtCl2 ergab den PtCl2-Komplex (11). Wie bei allen zuvor genannten Verbindungen, koordinieren nur zwei der Phosphoratome an Platin, während zwei Phosphoratome unkoordiniert bleiben (nachgewiesen durch die Signalmuster im 31P-NMR-Spektrum mit charakteristischen Werten für die 1J(PPt)-Kopplungskonstanten). NMR-spektroskopische Evidenz wurde auch für die Existenz der Konus-Konformation in der cis-Konfiguration von 11 gefunden.
    No preview · Article · Mar 2002 · Zeitschrift für anorganische Chemie
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    ABSTRACT: Going up! n-Selectivity and activity can be increased simultaneously in hydroformylation by the use of novel hybrid ligands such as 1 containing O-acylphosphite groups. For the first time these ligands deliver impressively n-selective rhodium-catalyzed hydroformylation of internal octenes, and this with an industrial relevant catalytic activity.
    No preview · Article · Jun 2001 · Angewandte Chemie International Edition