Neutral and ionic aluminum,gallium, and indium compounds carrying two or three terminal ethynyl groups

The syntheses of the ionic compounds [Li(+).2 dioxane (2,6-iPr(2)C(6)H(3)N(SiMe(3))Al(C triplebond CSiMe(3))(3))(-)].0.75 dioxane (1), [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))Ga(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (2), and [(Li(+))(2).(dioxane)(7)](0.5) [2,6-iPr(2)C(6)H(3)N(SiMe(3))In(C triplebond CSiMe(3))(3)(-)].1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiC triplebond CSiMe(3) are reported. The neutral ethynyl compounds Br-Al(C triplebond CtBu)(2).2 THF (4), Cl-Ga(C triplebond CtBu)(2).THF (5), Cl-In(C triplebond CtBu)(2).2 THF (6), Al(C triplebond CtBu)(3).C[N(Me)CMe](2) (7), Ga(C triplebond CtBu)(3).dioxane (8), and In(C triplebond CtBu)(3).NEt(3) (9) have been obtained in good yields from the reaction of AlBr(3), GaCl(3), and InCl(3) with LiC triplebond CtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(C triplebond CPh)(3).NMe(3) (10) and Ga(C triplebond CPh)(3).NMe(3) (11) have been prepared by the reaction of AlH(3).NMe(3) or GaH(3).NMe(3) with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units.     

Precise atomic masses of147Eu,147Gd,and151Tb derived from their decay properties

Theβ-decay energies of¹⁴⁷Eu,¹⁴⁷Gd, and¹⁵¹Tb were determined by usingγ-spectroscopical methods. The comparison of experimental with calculatedK-capture probabilities yielded theQ _EC values 1.690( _?16 ⁺²¹ )MeV and 2.203( _?13 ⁺¹⁹ )MeV for¹⁴⁷Eu and¹⁴⁷Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in¹⁴⁷Eu decay, the decay energiesQ _EC=1.702(13) MeV andQ _EC=1.709(18)MeV were derived. Also fromEC/β ⁺ ratios the valuesQ _EC=2.225(75) MeV for¹⁴⁷Gd, andQ _EC=2.566(12)MeV for¹⁵¹Tb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studiesγ-decay properties of¹⁴⁷Eu and¹⁴⁷Gd were reinvestigated.     

Lateral growth rates in laser CVD of microstructures

Lateral growth rates of Ni spots deposited on absorbing substrates by decomposition of Ni(CO)₄ with visible Kr⁺ laser light have been measured. The experimental data are consistent with the calculated temperature distributions. The mechanism of decomposition is thermal with an apparent chemical activation energy of 22±3 kcal/mole for the temperature range 350 KT500 K.     

Thermal and autoxidation reactions of poly-3-methylenecyclobutene and poly-1-methyl-3-methylenecyclobutene

The thermal ring-opening reactions, autoxidation and hydrogenation of polymethy-lenecyclobutene (PMCB) and poly-1-methyl-3-methylenecyclobutene (PMMCB), were investigated. Both polymers were prepared by cationic polymerization and consisted almost entirely of 1,5-repeating units containing cyclobutene rings in the polymer backbone. Both polymers showed well behaved exothermic processes at elevated temperatures which apparently resulted in crosslinking. These processes were investigated by differential scanning calorimetry and interpreted to involve thermal ring-opening reactions. Autoxidation occurred very rapidly in PMCB but much more slowly in PMMCB as predicted by Bolland's rules. Attempts to hydrogenate the cyclobutene rings in both polymers resulted in the occurrence of hydrogenolysis in PMCB and little or no reaction with PMMCB for a Pd-catalyzed reaction and partial hydrogenation of the latter for a diimide reaction.     

Gas-phase on-line generation and infrared spectroscopic investigations of polyphosphazenes, (NPX2)3 where X=F, Cl and Br

Gas-phase infrared spectra of polyphosphazenes (phosphonitrilic halides trimer), (NPX2)3 where X=F, Cl and Br have been recorded. The molecules were generated for the first time by an on-line process using solid (NPCl2)3 as a precursor passed over heated sodium fluoride and potassium bromide at about 550 and 700 degrees C for (NPF2)3 and (NPBr2)3 production, respectively. The products were characterized by the infrared spectra of their vapors. The low-resolution gas-phase Fourier transform infrared spectra reported for the first time show strong bands centered at 1295, 1215 and 1200 cm-1, assigned to nu7(E'), in plane PN stretching mode of (NPX2)3, where X=F, Cl and Br, respectively.     

Determination of the enantiomeric composition of guest molecules by chemometric analysis of the UV-visible spectra of cyclodextrin guest-host complexes

Multivariate statistical techniques were applied to the UV spectra of a series of solutions at pH 12 containing a fixed concentration (30 mM) of beta-cyclodextrin (beta-CD) and a fixed concentration (15 mM) of 2-phenylglycine (phi-Gly) with various known enantiomeric compositions. Multivariate correlation of the spectral data for the solutions containing the phi-Gly/beta-CD guest-host complexes with the known enantiomeric composition of the phi-Gly samples was accomplished by partial-least-squares regression. When the multivariate model was used to predict the enantiomeric purity of a test set of samples over the mol fraction range of 0.5-0.9 R-phi-Gly, the average magnitude of the relative errors in the mol fraction determination of enantiomeric composition was 3%. A plot of the enantiomeric composition predicted by the model versus the known enantiomeric composition of the calibration set gave a straight line with a correlation coefficient of 0.955, a slope of 1.05, and an offset of 5.61 x 10-4.     

Snapshots of dioxygen activation by copper: the structure of a 1:1 Cu/O(2) adduct and its use in syntheses of asymmetric Bis(mu-oxo) complexes

The X-ray structure of a 1:1 Cu/O(2) adduct revealed side-on (eta(2)) O(2) coordination. Density functional calculations corroborated the structure, indicated a significant contribution of a Cu(III)-(O(2)(2-)) resonance form, and provided insights into the key bonding interactions. Reaction of a 1:1 adduct supported by a slightly different beta-diketiminate ligand with Cu(I) reagents resulted in the formation of novel asymmetric bis(mu-oxo) complexes that were identified by EPR, UV-vis, and Raman spectroscopy, as well as by an X-ray structure in one instance.     

Immuno-affinity columns versus conventional clean-up: a method-comparison study for the determination of zearalenone in corn

The efficiency of a modern analytical method employing immuno-affinity columns (IACs) is compared to a well established traditional technique with respect to the determination of zearalenone (ZON) in corn in the μg/kg range. Despite of a constant error of about 4 μg/kg in the examined working range of 10–200 μg/kg, analytical data obtained from the analysis of spiked and naturally contaminated samples showed good correspondence for the compared methods. The performance characteristics of immuno-affinity-chromatography as a new clean-up technique for the determination of ZON in corn is reported for the first time and compared to a conventional clean-up procedure     

Use of γ-γ Coincidence Spectrometry in the Geochemical Study of Diamictites from South Africa

We used - coincidence spectrometry to investigate the possible presence of a meteoritical component in 27 samples of South African diamictites. Recently, several studies have suggested that some tillites/diamictites may represent impact breccias, but a petrographical study by our group found no evidence for the presence of impact-characteristic shocked minerals. The siderophile elements, such as Cr, Co, Ni, and, especially, the platinum group elements, have high abundances in meteorites, but low abundances in terrestrial crustal rocks. The Ir content of the diamictites was measured with the new iridium coincidence spectrometer (ICS) at the University of Vienna, with detection limits of around 0.02 ppb. No enrichments in the contents of Ir and other siderophile elements compared to average crustal concentrations were found; thus, no unequivocal evidence for an impact origin of these diamictites of the South African Dwyka Group can be documented.     

Coordination complexes of acetylenic phosphines and diphosphines

The reactions of π-cyclopentadienylnickel carbonyl dimer with 3,3,3-trimethylpropynyldiphenylphosphine and phenylethynyldiphenylphosphine are described. The products have been characterized by elemental and mass spectral analysis, infrared and NMR spectroscopy. An acetylene bridged complex (π-C₅H₅Ni)₂Ph₂PC₂-t-Bu, containing an uncoordinated phosphorus atom, has been prepared. The complex can be oxidized to the phosphine oxide derivative (π-C₅H₅Ni)₂Ph₂P(O)C₂-t-Bu and converted to the phosphonium salts with methyl iodide or ethyl bromide. These are the first reported π-complexes of phosphonium salts. The complex (π-C₅H₅Ni)₂Ph₂PC₂-t-Bu forms the novel mixed metal derivative [PdCl₂][(π-C₅H₅Ni)₂Ph₂PC₂-t-Bu]₂ from bis(benzonitrile)-palladium dichloride. The dicarbonyl complexes Ni(CO)₂(Ph₂PC₂R)₂ (R  t-Bu, Ph), the phosphine oxide complex (π-C₅H₅Ni)₂(Ph₂P(O)C₂Ph) and the trinuclear nickel carbonyl derivative Ni(CO)₃[(π-C₅H₅Ni)₂Ph₂PC₂Ph] are described.