[Ph2P(O)CH2Im][F3B(μ‐OH)BF3]. Erste strukturanalytische Charakterisierung des Hexafluoro(μ‐hydroxo)diborat‐Ions [1]

Kühn, Norbert; Göhner, Martin; Steimann, Manfred

doi:10.1002/zaac.200390100

Cited by 9 publications

(8 citation statements)

References 11 publications

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“…The complex can be seen as a protonation product upon addition of the hypothetical acid H[HOB 2 F 6 ] at the Lewis base 5 , and the crystal structure of the dimer unit is shown in Figure 3. The unusual and as yet unique anion [HOB 2 F 6 ] – was described earlier with a carbenoid counter cation 20. The bonding situation around the P–C–P group changed dramatically upon conversion of the central sp 2 carbon atom into a sp 3 carbon atom on protonation to give a type C salt.…”

Section: Crystal Structuresmentioning

confidence: 92%

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Nam

Park

2001

J of Applied Polymer Sci

142

116

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Regenerated silk fibroin (RSF) was prepared by dissolving in a CaCl 2 / ethanol/H 2 O solvent system, freezing, and lyophilization. The effect of freezing temperature, alcohol addition, and molecular weight on the morphological and conformational changes were investigated through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, circular dichroism spectroscopy, and differential scanning calorimetry analysis. However, the addition of a small amount of methanol induced the morphological change of RSF to a fine-particle aggregate, which resulted from the formation of a ␤-sheet crystalline structure. The lower the freezing temperature was, the more the formation of aggregates was favored, and the finer powder aggregates were formed. As the amount of added hydrophilic alcohol such as methanol and ethanol increased in the silk fibroin solution, a spherical powder form was changed to fine aggregates with the enhancement of thermal stability and crystallinity. On the other hand, RSFs prepared with a hydrophobic alcohol such as 1-butanol or 1-octanol showed a lump-like or sheet-like shape of morphology without any changes in conformational transition. It is concluded that the molecular weight of the silk fibroin and the type and amount of alcohol were determining factors in the morphological features of RSF, especially the size and shape of fibroin particles. A uniform ultrafine powder of RSF with a spherical form (ϳ 1 m) can be obtained when the molecular weight and the alcohol addition to the silk fibroin solution are controlled.

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Section: Crystal Structuresmentioning

confidence: 92%

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Nam

Park

2001

J of Applied Polymer Sci

142

116

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“…The metal hydride distance was allowed to refine, but the H atom U ’s were assigned as 1.5x U eq of the carrier atom (The carrier atom was assumed to be Fe1 because the Fe-H distance was shorter than the Ni-H distance). The hydroxyl atom on the counterion 42 was located in the difference map. The O-H bond distance was allowed to refine, but the H atom U ’s were assigned as 1.5x U eq of the carrier O atom.…”

Section: Methodsmentioning

confidence: 99%

Active-Site Models for the Nickel–Iron Hydrogenases: Effects of Ligands on Reactivity and Catalytic Properties

et al. 2011

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Described are new derivatives of the type [HNiFe(SR)2(diphosphine)(CO)3]+, which feature a Ni(diphosphine) group linked to a Fe(CO)3 group via two bridging thiolate ligands. Previous work had described [HNiFe(pdt)(dppe)(CO)3]+ ([1H]+) and its activity as a catalyst for the reduction of protons. Work described in this paper focused on the effects of the diphosphine attached to nickel as well as the dithiolate bridge, 1,3-propanedithiolate (pdt) vs 1,2-ethanedithiolate (edt). A new synthetic route to these Ni-Fe dithiolates is described, involving reaction of Ni(SR)2(diphosphine) with FeI2(CO)4 followed by in situ reduction with cobaltocene. Evidence is presented that this route proceeds via metastable μ-iodo derivatives. Attempted isolation of such species led to the crystallization of NiFe(Me2pdt)(dppe)I2, which features tetrahedral Fe(II) and square planar Ni(II) centers (Me2pdt = 2,2-dimethylpropanedithiol). The new tricarbonyls prepared in this work are NiFe(pdt)(dcpe)(CO)3 (2, dcpe = 1,2-bis(dicyclohexylphosphino)ethane), NiFe(edt)(dppe)(CO)3 (3), and NiFe(edt)(dcpe)(CO)3 (4). Attempted preparation of a phenylthiolate-bridged complex via the FeI2(CO)4 + Ni(SPh)2(dppe) route gave the tetrametallic species [(CO)2Fe(SPh)2Ni(CO)]2(μ-dppe)2. Crystallographic analysis of the edt-dcpe compund [2H]BF4 and the edt-dppe compound [3H]BF4 verified their close resemblance. Each features pseudo-octahedral Fe and square pyramidal Ni centers. Starting from [4H]BF4 we prepared the PPh3 derivative [HNiFe(edt)(dppe)(PPh3)(CO)2]BF4 ([5H]BF4), which was obtained as a ~2:1 mixture of unsymmetrical and symmetrical isomers. Acid-base measurements indicate that changing from Ni(dppe) to Ni(dcpe) decreases the acidity of the cationic hydride complexes by 2.5 pKaMeCN units, from ~11 to ~13.5 (previous work showed that substitution at Fe leads to more dramatic effects). The redox potentials are more strongly affected by the change from dppe to dcpe, for example the [2]0/+ couple occurs at E1/2 = −820 for [2]0/+ vs −574 mV (vs Fc+/0) for [1]0/+. Changes in the dithiolate do not affect the acidity or the reduction potentials of the hydrides. The acid-independent rate of reduction of CH2ClCO2H by [2H]+ is ca. 50 s−1 (25 °C), twice that of [1H]+. The edt-dppe complex [2H]+ proved to be the most active catalyst, with an acid-independent rate of 300 s−1.

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“…Selected bond lengths/pm and angles/° in 5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 15 and as yet unique anion [HOB 2 F 6 ] − was described earlier with a carbenoid counter cation [20]. The bonding situation around the P-C-P group changed dramatically upon conversion of the central sp 2 carbon atom into a sp 3 carbon atom on protonation to give a type C salt.…”

Section: Crystal Structuresmentioning

confidence: 96%

Formation and Crystal Structures of Lewis Acid Adducts of Ph₃PCHP(O)Ph₂; New Neutral and Cationic Species

Petz

Öxler

Aicher

et al. 2010

Zeitschrift anorg allge chemie

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Abstract. The carbodiphosphorane C(PPh 3 ) 2 (1) is easily hydrolyzed from wet air to give the ylide Ph 3 PCHP(O)Ph 2 (2), which forms addition compounds with various Lewis acids to give neutral or cationic compounds. According to pairs of electrons at the central carbon atom and the oxygen atom, respectively, addition compounds with coordination modes A (via oxygen), B (via carbon), and C (via carbon and oxygen) were isolated either as by-products from reactions of Lewis acids with 1 (contaminated with some 2) or directly with 2. The crystal structures and the spectroscopic properties of 2 and of the addition

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[Ph₂P(O)CH₂Im][F₃B(μ‐OH)BF₃]. Erste strukturanalytische Charakterisierung des Hexafluoro(μ‐hydroxo)diborat‐Ions [1]

Cited by 9 publications

References 11 publications

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Active-Site Models for the Nickel–Iron Hydrogenases: Effects of Ligands on Reactivity and Catalytic Properties

Formation and Crystal Structures of Lewis Acid Adducts of Ph₃PCHP(O)Ph₂; New Neutral and Cationic Species

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[Ph2P(O)CH2Im][F3B(μ‐OH)BF3]. Erste strukturanalytische Charakterisierung des Hexafluoro(μ‐hydroxo)diborat‐Ions [1]

Cited by 9 publications

References 11 publications

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight

Active-Site Models for the Nickel–Iron Hydrogenases: Effects of Ligands on Reactivity and Catalytic Properties

Formation and Crystal Structures of Lewis Acid Adducts of Ph3PCHP(O)Ph2; New Neutral and Cationic Species

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Product

Resources

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[Ph₂P(O)CH₂Im][F₃B(μ‐OH)BF₃]. Erste strukturanalytische Charakterisierung des Hexafluoro(μ‐hydroxo)diborat‐Ions [1]

Formation and Crystal Structures of Lewis Acid Adducts of Ph₃PCHP(O)Ph₂; New Neutral and Cationic Species