Schwingungsspektren und Kraftkonstanten von W(OCH3)6, Mo(OCH3)6 und [Sb(CH3)4][Sb(OCH3)6]

Vibrational Spectra and Force Constants of W(OCH₃)₆, Mo(OCH₃)₆, and [Sb(CH₃)₄][Sb(OCH₃)₆] The infrared and Raman spectra of the monomeric hexamethoxides of Tungsten and Molybdenum and of the ionic compound [Me₄Sb]⁺[Sb(OMe)₆]^? (prepared from [Sb(OMe)₅]₂ and Me₄SbOMe; Me = CH₃) are recorded and interpreted on the basis of C_3i symmetry. The force fields of W(OMe)₆ and [Sb(OMe)₆]^? are calculated using the same basis set of force constants. Both W? O- and Sb? O- stretching force constants are identical (2.56 N/cm), however the other parts of the valence force field are markedly different.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XI [1]. Bildung,Reaktionen und Strukturen von Chromcarbonylkomplexen aus Reaktionen von Li(THF)2[η2-(tBu2P)2P] mit Cr(CO)5 · THF und Cr(CO)4 · NBD

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. XI. Formation, Reactions, and Structures of Chromium Carbonyl Complexes from Reactions of Li(THF)₂[η₂-(^tBu₂P)₂P] with Cr(CO)₅ · THF and Cr(CO)₄ · NBD Reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 1 with Cr(CO)₅ · THF yield Li(THF)₂Et₂O[Cr(CO)₄{η²-(^tBu₂P)₂P}η¹-Cr(CO)₅] 2 and the compounds [Cr(CO)₄{η²-(^tBu₂P)₂PH}] 3 , [Cr(CO)₅{η¹-(^tBu₂P)₂PH}] 4 , (^tBu₂P)₂PH 5 and ^tBu₂PH · Cr(CO)₅ 6 . The formation of 3, 4, 5 and 6 is due to byproducts coming from the synthesis of 1. 2 reacts with CH₃COOH under formation of 3 . After addition of 12-crown-4 1 with NBD · Cr(CO)₄ in THF forms Li(12-crown-4)₂[Cr(CO)₄-{η²-(^tBu₂P)₂P}] 7 (yellow crystals). 7 reacts with CH₃COOH to 3 – which regenerates 7 with LiBu – with Cr(CO)₅THF to compound 2 , with NBD · Cr(CO)₄ in THF to 2 and 3 (ratio 1 : 1). With EtBr, 7 forms [Cr(CO)₄{η²-(^tBu₂P)₂PEt}] 8 , and [Cr(CO)₄{η²-(^tBu₂P)₂PBr}] 9 with BrCH₂? CH₂Br. The compounds were characterized by means of ¹H, ¹³C, ³¹P, ⁷Li NMR spectroscopy, IR spectroscopy, elementary analysis, mass spectra, and 2, 3 and 4 additionally by means of X-ray diffraction analysis. 2 crystallizes in the space group P1 with 2 formula units in the elementary cell; a = 10.137(9), b = 15.295(12), c = 15.897(14) Å; α = 101.82(7), β = 91.65(7), γ = 98.99(7)°; 3 crystallizes in the space group P2_t/n with 4 molecules in the elementary unit; a = 11.914(6), b = 15.217(10), c = 14.534(10) Å; α = 90, β = 103.56(5), γ = 90°. 4 : space group P1 with 2 molecules in the elementary unit; a = 8.844(4), b = 12.291(6), c = 14.411(7) Å, α = 66.55(2), β = 89.27(2), γ = 71.44(2)°.     

Zum Einfluß der Substituenten R = Ph,NEt2, iPr und tBu in Triphosphanen, (R2P)2P?SiMe3, und Phosphiden,Li(THF)2[(R2P)2P], auf die Bildung und Eigenschaften von Phosphinophosphiniden-Phosphoranen

Concerning the Influence of the Substituents R = Ph, NEt₂, ⁱPr, and ^tBu in Triphosphanes (R₂P)₂P? SiMe₃ and Phosphides Li(THF)₂[(R₂P)₂P] on the Formation and Properties of Phosphino-phosphinidene-phosphoranes The triphosphanes X₂P? P(SiMe₃)? PY₂ 5, 7, 9, 11, 13 and the derived phosphides Li(THF)₂[X₂P? P? PY₂] 6, 8, 10, 12, 14 were synthesized: 5 and 6 with X₂ = ⁱPr₂ and Y₂ = ^tBu₂, 7 and 8 with X₂ = Y₂ = Ph^tBu, 9 and 10 with X₂ = ^tBu₂ and Y₂ = Ph₂, 11 and 12 with X₂ = Y₂ = Ph₂, and 13 and 14 with X₂ = ^tBu₂ and Y₂ = (NEt₂)₂. The silylated triphosphanes at ?70°C in toluene with CBr₄ may yield X₂P? P?P(Br)Y₂ and X₂P? P(Br)? PY₂, and the lithiated phosphides with MeCl may yield X₂P? P?P(Me)Y₂ and X₂P? P(Me)? PY₂ depending on X and Y. The bromiated product of 5 (X₂ = ⁱPr₂, Y₂ = ^tBu₂) is the ylide ⁱPr₂P? P?P(Br)^tBu₂, and the methylated derivatives of 6 are both ⁱPr₂P? P?P(Me)^tBu₂, ^tBu₂P? P?P(Me)ⁱPr and the methylated triphosphane. Ph₂P? P?P(Br)^tBu₂ as well as the brominated triphosphane are obtained from 9 (X₂ = ^tBu₂, Y₂ = Ph₂), and similarly Ph₂P? P?P(Me)^tBu₂ and the methylated triphosphane from 10 . Compound 14 (X₂ = ^tBu₂, Y₂ = (NEt₂)₂ gives rise to the brominated ylide ^tBu₂)P? P?P(Br) · (NEt₂)₂ and to the brominated triphosphane, and on methylation to ^tBu₂P? P?P(Me)(NEt₂)₂ and to ^tBu₂P? P(Me)? P · (NEt₂)₂ (main product). The Br substituted derivatives decompose already on warming to ?30°C, while the methylated compounds are stable up to 20°C.     

Borchelate und Bormetallchelate,V1

Substitution of only one bridged hydrogen atom of bis(1,2-cycloheptanedionedioximato)nickel(II) by the diphenylboron group is easily accomplished with formation of1. Both hydroxy groups of bis(dihydroxyboron-diaminoglyoximato)nickel(II) chelate² can be esterified by phenol or methanol (chelates2 a andb). The bis(diphenylboron) chelate3 a results from the reaction of bis(dihydroxyborondiaminoglyoximato)nickel(II) with diphenylboric anhydride. In the same way the corresponding chelates3 b-f are obtainable from the boron-free nickel chelates. The i.r. and u.v. spectra as well as the diamagnetic character of the compounds described are in agreement with planar structures.

IV. Mitt.:E. Hohaus, Mh. Chem., im Druck.     

Mass spectrometry of hyper‐velocity impacts of organic micrograins

The study of hyper‐velocity impacts of micrometeoroids is important for the calibration of dust sensors in space applications. For this purpose, submicron‐sized synthetic dust grains comprising either polystyrene or poly[bis(4‐vinylthiophenyl)sulfide] were coated with an ultrathin overlayer of an electrically conductive organic polymer (either polypyrrole or polyaniline) and were accelerated to speeds between 3 and 35 km s^?1 using the Heidelberg Dust Accelerator facility. Time‐of‐flight mass spectrometry was applied to analyse the resulting ionic impact plasma using a newly developed Large Area Mass Analyser (LAMA). Depending on the projectile type and the impact speed, both aliphatic and aromatic molecular ions and cluster species were identified in the mass spectra with masses up to 400 u. Clusters resulting from the target material (silver) and mixed clusters of target and projectile species were also observed. Impact velocities of between 10 and 35 km s^?1 are suitable for a principal identification of organic materials in micrometeoroids, whereas impact speeds below ～10 km s^?1 allow for an even more detailed analysis. Molecular ions and fragments reflect components of the parent molecule, providing determination of even complex organic molecules embedded in a dust grain. In contrast to previous measurements with the Cosmic Dust Analyser instrument, the employed LAMA instrument has a seven times higher mass resolution – approximately 200 – which allowed for a detailed analysis of the complex mass spectra. These fundamental studies are expected to enhance our understanding of cometary, interplanetary and interstellar dust grains, which travel at similar hyper‐velocities and are known to contain both aliphatic and aromatic organic compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of electrochemical behavior of the Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles in aprotic media

Peculiarities of electrochemical behavior of the Fe₃O₄ magnetic nanoparticles immobilized on the surface of a platinum electrode in aprotic organic media were investigated. Possible scheme of electrochemical behavior of nanoparticles depending on pre-electrolysis potential (–1.3,–2.5 V) was suggested. The effect of pre-electrolysis time, potential scan rate and nature of supporting electrolyte on the processes investigated was determined. A linear dependence of electrochemical oxidation signal versus the concentration of nanoparticles in modifying suspension in the concentration range of 0.05—0.5 g L^–1 was observed. The results of the performed research allow using magnetite nanoparticles as a direct signal-generating label in electrochemical immunoassay.     

Recent improvements in the methodology of neutron imaging

The focus of this article is on further improvements of methods in neutron imaging: the increased spatial resolution for microtomography and options for energy-selective neutron imaging. Before going into details, some common statements are given in respect to the state-of-the-art in neutron imaging. A relation to the X-ray methods is mentioned, where complementary results are obtained. The potential for the energy selection is of particular interest for future installations at the new pulsed sources, based on spallation (SNS, J-PARC, ISIS-TS2). First results from preliminary studies look very promising for future material and industrial research. Therefore, statements about the set-up of the best possible imaging systems are included in the article.