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52. Nondestructive identification of colloidal molecular sieves stabilized in water

Author

T. H. Metzger, Karaghiosoff K, Boriana Mihailova, Thomas Bein, and Svetlana Mintova

Subjects
Materials science, Inorganic chemistry, Microporous material, Carbon-13 NMR, Molecular sieve, Surfaces, Coatings and Films, law.invention, Crystallinity, symbols.namesake, Chemical engineering, law, Materials Chemistry, symbols, Molecule, Physical and Theoretical Chemistry, Crystallization, Zeolite, Raman spectroscopy
Abstract

The encapsulation of small quaternary ammonium ions in zeolite frameworks could be used as a base for investigation of the crystallization process of colloidal (nanosized) molecular sieves stabilized in water with Raman and (13)C NMR spectroscopic methods. The organic-framework interactions in colloidal microporous materials with LTA, FAU, BEA, and MFI topology have been considered; the results show that the crystallinity of nanosized particles with monomodal particle size distribution stabilized in water can be examined using the vibrational and magnetic resonance spectral features of the organic template molecules occluded in the specific pores and cages in the zeolite framework. The molecular packing effect and restricted mobility due to specific organic/framework interactions result in shifts and substantial broadening of the (13)C NMR signals, as well as in changes of the positions and the relative intensities of the Raman peaks. The spectroscopic methods are very efficient for analyzing the crystalline structures of nanosized molecular sieves stabilized in aqueous suspensions due to no restrictions related to the particle size.

Published
2006

60. Reactions of hydroxyl-containing compounds with tert-butyl hydroperoxide in the presence of chromium tetra- tert-butoxide.

Author

Fukin, G., Stepovik, L., Zaburdaeva, E., and Karaghiosoff, K.

Subjects
OXIDATION of chemical alcohols, HYDROPEROXIDES, ORGANOCHROMIUM compounds, PINACOLS, CATECHOL derivatives, GLYCOLS
Abstract

Primary and secondary aliphatic, alkylaromatic, cyclic, and organoelement alcohols are efficiently oxidized by tert-butyl hydroperoxide in the presence of both equimolar and catalytic quantities of chromium tetra-tert-butoxide (СН, 20°С). α-Diols containing tertiary hydroxyl groups interact with this system via oxidative splitting of the carbon scaffold. The oxidation includes the stages of formation and decomposition of chromium-containing peroxy compounds. Further transformations of the carbonyl compounds depend on the structure of radicals in the molecules. [ABSTRACT FROM AUTHOR]

Published
2015
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86. Nucleophilic Degradation of White Phosphorus with tBu<INF>3</INF>SiK:  Synthesis and X-ray Crystal Structure Analysis of the Potassium Triphosphide (tBu<INF>3</INF>Si)<INF>2</INF>P<INF>3</INF>K

Author

Lerner, H.-W., Bolte, M., Karaghiosoff, K., and Wagner, M.

Abstract

The potassium phosphides (tBu3Si)2P4K2 and (tBu3Si)4P8K4 can be synthesized from the reaction of P4 with 2 equiv of the potassium silanide tBu3SiK in tetrahydrofuran at −78 °C. The potassium silanide tBu3SiK slowly transforms the tetraphospide (tBu3Si)2P4K2 and the octaphosphide (tBu3Si)4P8K4 into (tBu3Si)2P3K and (tBu3Si)3P5K2. X-ray quality crystals of the triphosphide, tBu3SiKP−P&dbd;PSitBu3, have been obtained from a tetrahydrofuran solution at −25 °C.

Published
2004

87. Synthesis and investigation of new phosphorus-chalcogen compounds.

Author

Poller, M. J., Huber, T., Frickel, J., Burford, N., and Karaghiosoff, K.

Subjects
NONMETALS, SELENIUM, NUCLEAR magnetic resonance spectroscopy, SINGLE crystals, X-ray diffraction, SULFUR
Abstract

Ionic compounds containing phosphorus-based cations represent an important new direction in the fundamental chemistry of nonmetal elements. In this work, we explored the reactivity of phosphino-phosphonium cations with sulfur and selenium, with a view towards new synthetic methods for phosphorus-chalcogen cations. We present several new cations which have been identified by 31P NMR spectroscopy and single crystal x-ray diffraction, that are analogous to the recently reported chalcogenides of phosphanylboranes. We also present new diphosphonium-diselenide cations which have been formed through a unique redox equilibrium of triphenylantimony(V) bistriflate and trialkylphosphineselenides on one side and the diphosphonium diselenide cations and triphenylantimony(III) on the other side. [ABSTRACT FROM AUTHOR]

Published
2019
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88. Reactivity of phosphines with iodomethane analog fluoroiodomethane.

Author

Reichel, M., Martens, J., Unger, C. C., and Karaghiosoff, K.

Subjects
PHOSPHONIUM compounds, WITTIG reaction, METHYL iodide, CRYSTAL structure
Abstract

Reactions of phosphines with iodomethane are well known and well investigated. The resulting phosphonium salts are used in Wittig reactions or to form ionic liquids. Reaction rates depend on the Tollman parameter as well as on steric factors. Reactions with iodomethane occur spontaneously within a few hours. We have found that the corresponding reactions of phosphines with fluoroiodomethane are significantly slower. Reaction times range from one day up to 11 days. The resulting phosphonium salts are stable towards air and water and show also low aqueous toxicity with respect to Vibrio fisheri bacteria. Due to the strong electronegativity of the fluorine atom and its similarity to an OH group, interesting crystal structures were observed. [ABSTRACT FROM AUTHOR]

Published
2019
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89. Synthesis and Structures of Lithium and Potassium Complexes of Phosphanyl-Substituted Bis[1,3-bis(trimethylsilyl)cyclopentadienyl]yttriates

Author

Westerhausen, M., Schneiderbauer, S., Makropoulos, N., Warchhold, M., Noth, H., Piotrowski, H., and Karaghiosoff, K.

Abstract

The metathesis reaction of [(THF)4Li][Cp‘ ‘2Li] (1) (Cp‘ ‘ = 1,3-(Me3Si)2C5H3) with yttrium trichloride yields bis(tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl]dichloroyttriate (2). The metathesis reaction of 2 with potassium (triisopropylsilyl)phosphanide in toluene gives a stepwise exchange of the chloride ligands with the phosphanide substituents. In contrast to bis(tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][(triisopropylsilyl)phosphanyl]chloroyttriate (3), which appears as an intermediate observable by NMR spectroscopy, (tetrahydrofuran)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][bis(triisopropylsilyl)phosphanyl]yttriate (4) is isolated as a colorless crystalline material with a YP2Li cycle and Y−P bond lengths of 2.840 Å. In solution a dissociation is observed into lithium (triisopropylsilyl)phosphanide and the THF complex of bis[1,3-bis(trimethylsilyl)cyclopentadienyl][(triisopropylsilyl)phosphanyl]yttrium (5). The reaction of either 2 or 4 with potassium (triisopropylsilyl)phosphanide in benzene yields (η6-benzene)potassium bis[1,3-bis(trimethylsilyl)cyclopentadienyl][bis(triisopropylsilyl)phosphanyl]yttriate (6) with a YP2K cycle and Y−P distances of 2.846 Å. The metathesis reaction of 2 with (DME)LiPH2 gives (1,2-dimethoxyethane)lithium bis[1,3-bis(trimethylsilyl)cyclopentadienyl]bis(phosphanyl)yttriate, which reacts with TMEDA to give colorless bis[(TMEDA)lithium] bis[1,3-bis(trimethylsilyl)cyclopentadienyl]bis(phosphanyl)yttriate chloride (7). The central YP2Li2Cl cycle is nearly planar with Y−P bond lengths of 2.849 Å.

Published
2002

90. Metalated 1,3-Azaphospholes:  Structure and Reactivity of 2-Lithio-1-methyl-1,3-benzazaphosphole, an Isolable −P&dbd;C(Li)−NR Heterocycle

Author

Heinicke, J., Steinhauser, K., Peulecke, N., Spannenberg, A., Mayer, P., and Karaghiosoff, K.

Abstract

The preparation, NMR data, a crystal structure, and the reactivity of isolable 2-lithio-1,3-benzazaphospholes are described. The compounds are or belong to the most stable P&dbd;CLi species, although they lack steric congestion. Reactions with organoelement or organometal halides W(CO)6 as well as with CO2 or benzophenone allow access to various novel functionally substituted 1,3-benzazaphospholes (2-R = SnMe3, Fe(CO)2Cp, C[&dbd;W(CO)5]OLi(THF)3, CPh2OH, PPh2, P(O)Ph2). The crystal structure of the tungsten-carbene derivative is described. Attempts to lithiate and functionalize a 1,3-benzazaphosphole P−W(CO)5 complex failed, but reactions of 1-methyl-2-stannyl- and 1-methyl-2-phosphino-1,3-benzazaphosphole with W(CO)5(THF) furnished examples for a 2-metalated benzazaphosphole P−W(CO)5 complex and the preferred complexation of the phosphino substituent, respectively. The considerable upfield shifts of the 31P NMR signals after complexation of the low-coordinated phosphorus atom by W(CO)5 attest that the ligands are stronger acceptors than donors.

Published
2002
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91. C−N Activation versus Metalation:  Reaction of Bis(methylzinc) 1,2-Bis((tert-butyldimethylsilyl)amido)-1,2-dipyridylethane with Acetamide and Aniline

Author

Westerhausen, M., Bollwein, T., Karaghiosoff, K., Schneiderbauer, S., Vogt, M., and Noth, H.

Abstract

The protonation of racemic (1S,2S)-bis(methylzinc) and (1R,2R)-bis(methylzinc) 1,2-bis((trialkylsilyl)amido)-1,2-dipyridylethane (2) with acetamide quantitatively yields racemic 1,2-bis((trialkylsilyl)amino)-1,2-dipyridylethane (3); the meso form 4 is not observed. Irradiation of 3 leads to an equilibrium mixture of all possible isomers, which have been detected by NMR spectroscopy. The crystal structures of 3 and 4 show elongated C−C bonds of the ethane backbone. Recrystallization of 3 from a water/acetone mixture resulted in precipitation of a water adduct of 3, which crystallizes in a chain structure with weak hydrogen bridges. The reaction of 2 with aniline gave bis(methylzinc) 1,2-bis(phenylamido)-1,2-dipyridylethane (5). Experiments with 15N-labeled aniline show that, however, the C−N, not the Si−N, bonds are cleaved.

Published
2002
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