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31.
Contributions to the Chemistry of Transition Metal Alkyl Compounds. 58 On 2-(Dimethylaminomethyl)ferrocenyl Compounds of Vanadium, Molybdenum, Tungsten, Thorium, and Uranium Earlier results according to which dimethylaminomethylferrocenyl groups (FcN) are able to form stable organometallic chelate compounds were confirmed by synthesis of the heterobimetallic chelate compounds (FcN)2VO · Li(acac) II , (FcN)MoO2(acac) III , (FcN)WOCl3 IV , (FcN)Th(acac)3 V , and (FcN)UO2(acac) VI from the corresponding metal acetylacetonates or oxidchlorides and (FcN)Li I . The new compounds were characterized by elemental analysis, the i.r., 1H-n.m.r., and electron spectra and by their effective magnetic moments. 相似文献
32.
Lorenz V Fischer A Jacob K Brüser W Edelmann FT 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(4):848-857
The preparation and structural characterization of scandium and f-element complexes derived from the disiloxanediolate dianion, [(Ph2SiO)2O]2-, are reported. Reactions of in situ prepared Ln[N(SiMe3)2]3 (Ln = Eu, Sm, Gd) with (Ph2SiOH)2O in different stoichiometries afforded the lanthanide disiloxanediolates [Eu[[(Ph2SiO)2O]Li(Et2O)]3] (1), [[[(Ph2SiO)2O]Li(dme)]2SmCl(dme)] (2), and [[[((Ph2SiO)2O]Li(thf)2]2GdN(SiMe3)2] (3). In situ formed (Ph2SiOLi)2O reacted with anhydrous NdBr3 (molar ratio 3:1) to give polymeric [[Nd[(Ph2SiO)2O]3[mu-Li(thf)]2[mu2LiBrLi(thf)(Et2O)]]n] (4). Treatment of 3 with Ph2Si(OH)2 in the presence of acetonitrile yielded the dilithium trisiloxanediolate derivative [[Ph2Si(OSiPh2O)2][Li(MeCN)]2]2 (5), which according to an X-ray analysis displays an Li4O4 heterocubane structure. The trinuclear scandium complex [[[(Ph2SiO)2O]Sc(acac)2]2Sc(acac)] (6) was obtained by reaction of [(C5Me5)Sc(acac)2] (C5Me5 = eta5-pentamethylcyclopentadienyl) with (Ph2SiOH)2O in a 3:2 molar ratio. Selective formation of the colorless uranium(VI) derivative [U[Ph2Si(OSiPh20)2]2[(Ph2SiO)2O]] (7) was observed when uranocene, U(eta8-C8H8)2, was allowed to react with (Ph2SiOH)2O. An X-ray diffraction study of the solvated derivative [U[Ph2Si(OSiPh2O)2]2[(Ph2SiO)2O]].Et2O.TMEDA (TMEDA= N,N,N',N'-tetramethyl-ethylenediamine) (7a) revealed the presence of both the original [(Ph2SiO)2O]2- dianion as well as the ring-enlarged [Ph2Si(OSiPh2O)2]2- ligand in the same molecule. 相似文献
33.
Tsamantakis C Masliyah J Yeung A Gentzis T 《Journal of colloid and interface science》2005,288(1):129-139
This study summarises the rheological behaviour of emulsion bitumen drops in the presence of aqueous solutions of de-ionised or process water (DIW or PW) containing montmorillonite clays (M) and/or calcium ions (Ca++). The presence of calcium ions and montmorillonite clays resulted in the plastic behaviour of bitumen drops. In a DIW+M+Ca++ system, increasing temperature and calcium ion concentration resulted in an increase in the number and degree of plastic bitumen drops. In the presence of considerable amounts of Ca++ ions and/or at higher experimental temperature, bitumen drops in a PW+M system exhibited no significant overall plasticity of their surfaces. Both calcium and sodium ions contained in process water compete with each other to occupy the montmorillonite clay surface. At the pH value of process water (pH congruent with8), increasing the temperature did not change the value of bitumen droplet zeta potential. Stability of bitumen-in-water emulsions at 22 degrees C showed that bitumen droplets coalesced upon contact in the DIW+M system. The addition of calcium ions (Ca++) led to the inhibition of coagulation and coalescence of bitumen droplets, which may indicate the formation of CaM aggregates at the bitumen-water interface. 相似文献
34.
Xu Q Souma Y Heaton BT Jacob C Kanamori K 《Angewandte Chemie (International ed. in English)》2000,39(1):208-209
Prolonged evacuation of [{Pt(CO)(3)}(2)](2+) (1), the first homoleptic, dinuclear, cationic platinum(I) carbonyl complex, results in reversible disproportionation. Complex 1 was formed by dissolution of PtO(2) in concentrated H(2)SO(4) under an atmosphere of CO [Eq. (a)], and completely characterized by NMR ((13)C, (195)Pt), IR, and Raman spectroscopy. 相似文献
35.
Koontz JL Phillips KM Wunderlich KM Exler J Holden JM Gebhardt SE Haytowitz DB 《Journal of AOAC International》2005,88(3):805-813
Analysis of total folate concentration measured by microbiological assay in a variety of foods submitted in a routine manner to experienced laboratories that regularly perform folate analysis on fee-for-service basis was evaluated. Homogenates of fresh strawberries, frozen spinach, orange juice, frozen meat and vegetable pizza, dry macaroni, and dried pinto beans were prepared and stored under conditions previously determined to maintain stability of folate content. An aliquot of each composite and of 3 certified reference materials were sent on each of 4 occasions to 4 laboratories. Results for macaroni and pizza, the only folic acid-fortified foods, had considerably lower between-laboratory variation (CV(B)) with CV(B) of 9-11% versus >45% for other foods. Mean total folate ranged from 14 to 279 microg/100 g for a mixed vegetable reference material, from 5 to 70 microg/100 g for strawberries, and from 28 to 81 microg/100 g for wholemeal flour. Only 1 laboratory reported using a tri-enzyme extraction, and all laboratories used folic acid fortified foods as internal control materials. Users of commercial total folate analysis should understand the uncertainty in values determined by microbiological assay, particularly for foods containing primarily naturally occurring folate, which may not be apparent when replicate samples are not submitted for analysis. 相似文献
36.
Thapper A Behrens A Fryxelius J Johansson MH Prestopino F Czaun M Rehder D Nordlander E 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3566-3571
Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented. 相似文献
37.
Abstract. Illumination of single-stranded φ×174 phage DNA with visible lightλ > 500 nm) in the presence of the sensitizer thiopyronine results in both chain scissions detectable by velocity sedimentation in neutral medium and in alkali-labile bonds which yield secondary strand breaks after alkaline treatment. Compared with the generation of primary strand breaks, the formation of alkali-labile sites seems to be the predominant reaction.
Photodynamic treatment of homogeneous double-stranded Ta, phage DNA leads to changes in the overall conformation of DNA as revealed by an initial increase of the sedimentation coefficient. The simultaneous occurrence of different effects (decrease of molecular weight, increase of effective DNA flexibility) is particularly evident from changes in the sedimentation coefficient distribution. The fact that both processes influence the sedimentation behaviour questions the common procedure of calculating double-strand break numbers from sedimentation coefficient distributions on the basis of s#-M relations which are valid for intact DNA only.
Photooxidized double-stranded DNA exhibits an increased sensitivity against shear forces. 相似文献
Photodynamic treatment of homogeneous double-stranded Ta, phage DNA leads to changes in the overall conformation of DNA as revealed by an initial increase of the sedimentation coefficient. The simultaneous occurrence of different effects (decrease of molecular weight, increase of effective DNA flexibility) is particularly evident from changes in the sedimentation coefficient distribution. The fact that both processes influence the sedimentation behaviour questions the common procedure of calculating double-strand break numbers from sedimentation coefficient distributions on the basis of s#-M relations which are valid for intact DNA only.
Photooxidized double-stranded DNA exhibits an increased sensitivity against shear forces. 相似文献
38.
Jacob D. Bekenstein 《General Relativity and Gravitation》1982,14(4):355-359
Black holes have piqued much curiosity. But thus far they have been important only in remote subjects like astrophysics and quantum gravity. We show that the situation can be improved. By a judicious application of black hole physics, one can obtain new results in everyday physics. For example, black holes yield a quantum universal upper bound on the entropy-to-energy ratio for ordinary thermodynamical systems which was unknown earlier. It can be checked, albeit with much labor, by ordinary statistical methods. Black holes set a limitation on the number of species of elementary particles-quarks, leptons, neutrinos-which may exist. And black holes lead to a fundamental limitation on the rate at which information can be transferred for given message energy by any communication system.This Essay received the first award from the Gravity Research Foundation for the year 1981-Ed. 相似文献
39.
Leslie C. Damude Philip A.W. Dean Michael D. Sefcik Jacob Schaefer 《Journal of organometallic chemistry》1982,226(2):105-114
The cross-polarization magic angle spinning 13C NMR spectra of Hg(SbF6)2 - 2 Arene (Arene = C6HMe5, 1,2,4,5-C6H2Me4, 1,2,3,4-C6H2Me4, or C6H6) have been measured. The spectra of the complexes of C6HMe5 and 1,2,4,5-C6H2Me4 are consistent with static η1-bonding of the mercury to the arene at an unsubstituted carbon atom, while the spectra of the 1,2,3,4-C6H2Me4 and C6H6 complexes show the arene to have time-averaged Cs or C2, and C6 symmetry respectively, at the temperature of measurement (300 K).The reduced temperature 13C NMR spectra of Hg(Arene)n2+ (n = 1 or 2; Arene = 1,3,5-C6H3R3 (R = Me, i-Pr, or t-Bu)) in SO2 solution are also reported and affirm that in these intramolecularly mobile species the mercury bonds in an η1-manner, with unsubstituted aryl carbon atoms being the strongly preferred point of mercury attachment. This site preference is further demonstrated by the solution 13C NMR spectra of Hg(Arene)n2+ (Arene = 1,2,3,4-C6H2-Me4, n = 1 or 2; Arene = 1,4-C6H4R2, R = Me or t-Bu, n = 1). The spectra of the 1,4-C6H4R2 complexes and Hg(p-C6H4-t-BuMe)2+ provide clear evidence for steric influence of the binding site.Like Hg(C6Me6)22+, but unlike most of the complexes of substituted benzenes which have been studied, Hg(1,3,5-C6H3-i-Pr3)22+ exchanges only slowly with excess free ligand. 相似文献
40.
X-ray diffraction analysis reveals the thiogermanic acid H(4)Ge(4)S(10) possesses discrete adamantane-like Ge(4)S(10)(4)(-) complex anions. Each thioanion is composed of four corner shared GeS(2.5)(-) tetrahedral units. Crystals were grown from anhydrous liquid hydrogen sulfide reactions with glassy germanium sulfide at room temperature. The crystal structure was solved and refined from single crystal diffractometer data (Mo Kalpha radiation) obtained at 173 K. H(4)Ge(4)S(10) is triclinic, centrosymmetric space group Ponemacr;, with a = 8.621(4) A, b = 9.899(4) A, c = 10.009(4) A, alpha = 85.963(7) degrees, beta = 64.714(7) degrees, gamma = 89.501(8) degrees, and Z = 2. Average bridging and terminal d(Ge-S) distances are 2.229 and 2.206 A, respectively. Vibrational mode assignments are reported from Raman scattering and IR absorption spectra of polycrystalline samples. The nu(s)(Ge-S-Ge) and nu(s)(Ge-S(-)) stretching modes are observed at 354 and 405 cm(-)(1), respectively. 相似文献