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Dr. H. Demel Dipl.-Ing H. J. Grießer Prof. Dr. K. Hummel 《Colloid and polymer science》1977,255(11):1131-1132
Ohne ZusammenfassungMit 1 Abbildung und 1 Tabelle 相似文献
4.
Structures of New SeII and TeII Complexes Containing 2,2-Dicyanethylene-1,1-dithiolate, 2,2-Dicyanethylene-1,1-thioselenolate, and 2,2-Dicyanethylene-1,1-diselenolate (NBu4)2{Se[S2C?C(CN)2]2} ( I ), (AsPh4)2 · {Te[SSeC?C(CN)2]2} ( II ), and (NBu4)2{Te[Se2C?C(CN)2]2} ( III ) containing the bidentate chelate ligands 2,2-dicyanethylene-1,1-dithiolate i-mnt , 2,2-dicyanethylene-1,1-thioselenolate i-mnts , and 2,2-dicyanethylene-1,1-diselenolate i-mns have been prepared and characterized by X-ray structure analysis. The central units consist of [M(X? X)2E2]2? (M = Se, Te; X? X = ligand; E = lone-pair) with fourfold coordinated SeII and TeII, respectively. The complex anions [Se(i-mnt)2E2]2? as well as [Te(i-mnts)2E2]2? show a trapezoide distortion with d(Se? S) = 2.276(5); 2.287(5); 2.803(5); 2.789(5) Å and d(Te? Se) = 2.611(2); 2.617(3); d(Te? S) = 2.889(5); 2.935(4) Å. In III there are centrosymmetric complex anions [Te(i-mns)2E2]2? with nearly identical Te? Se-bond-lengths: 2.674(3) and 2.692(2) Å. These Te? Se bonds are elongated compared to usual Te? Se bonds. 相似文献
5.
H.-J. Düssel A. Recca J. Kolb D.O. Hummel J.K. Stille 《Journal of Analytical and Applied Pyrolysis》1982,3(4):307-325
Pyrolysis—field ionization mass spectrometry was used for the investigation of the mechanism of the thermal degradation of polymeric heterocycles. Heat-resistant polymers containing aromatic and heterocyclic units such as polyquinolines and polyquinoxalines have a strong tendency to form large condensed systems during pyrolysis, and finally will carbonize. In the course of this process, side-groups (phenyl) and small fragments (NH3, HCN, acetonitrile, acrylonitrile, etc.) are split off. In addition, large heteroatom-containing fragments such as nitriles can be identified. These, together with some fragments that contain the complete heterocyclic ring, are characteristic of the chain building units (“key fragments”). Furthermore, compounds generated by recombination reactions and intramolecular cyclization are constituents of the pyrolysate. 相似文献
6.
Gröger H Hummel W Buchholz S Drauz K Nguyen TV Rollmann C Hüsken H Abokitse K 《Organic letters》2003,5(2):173-176
[reaction: see text] An enzyme-compatible biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration has been developed. In this biphasic reaction media, which is advantageous for reactions at higher substrate concentrations, both enzymes (alcohol dehydrogenase and FDH from Candida boidinii) remain stable. The reductions with poorly water-soluble ketones were carried out at substrate concentrations of 10-200 mM, and the optically active (S)-alcohols were formed with moderate to good conversions and with up to >99% ee. 相似文献
7.
Summary. This review reveals that, in contrast to the general opinion, the aqueous speciation of nickel is poorly known. Besides the
fairly well established first hydrolysis constant, data are scarce and only poor estimates can be derived for higher Ni hydrolysis
constants from a few solubility studies. The situation is even worse in the case of aqueous carbonate complexes. No reliable
experimental study has been published so far and almost all numbers reported in thermodynamic databases are unacceptable estimates.
In this review we scrutinise all these published estimates and propose expectation ranges of nickel carbonate complex stability
through correlation with other known thermodynamic constants. Solubility constants for a few simple nickel solids are known
or have been estimated from thermochemical data. However, none of these simple solids is of geochemical relevance at ambient
conditions. Based on field evidence, classes of solids are identified which potentially govern nickel concentrations in ground
and surface waters. Recent spectroscopic data indicate that magnesium clay minerals and layered double hydroxides are the
most prominent candidates for nickel-bearing solids at ambient conditions.
Corresponding author. E-mail: wolfgang.hummel@psi.ch
Dedicated to the memory of Prof. Rolf Grauer
Received January 14, 2003; accepted January 24, 2003
Published online May 15, 2003 相似文献
8.
An ion-exchange method was used to determine complexation constants for the Ni-oxalate and Ni-carbonate systems in a NaClO4 background electrolyte. The Ni-oxalate data were interpreted in terms of a single Niox(aq) complex having log K
1 values for Ni2+ + ox2– Niox(aq) of 3.9 ± 0.1 (I.S. = 0.5 mol-L–1 p[H] = 7.1) and 4.4 ± 0.1 (I.S. = 0.1 mol-L–1 p[H] = 8.6) at 22 ± 1C. Specific ion-interaction theory (SIT) was used to obtain log K
1
= 5.17 ± 0.05 (95% confidence level and = –0.23 ± 0.15) at I.S. = 0. The Ni-carbonate studies were carried out at p[H] values of 7.5, 8.5, and 9.6 in 0.5 mol-L–1 NaClO4/NaHCO3 solutions. The NiCO3(aq) species was the dominant complex in the [CO3
2–] concentration ranges studied at all three p[H] values. A log K
1 value for Ni2+ + CO3
2– NiCO3(aq) of 2.9 ± 0.3 was deduced at I.S. = 0.5 mol-L–1. Extrapolating this value to zero ionic strength using the SIT approach yielded log K
1
= 4.2 ± 0.3 (95% confidence level and = –0.26 ± 0.04). The data allowed upper bound values for the complexation constants for NiHCO3
+ and Ni(CO3)2
2– to be estimated, i.e., log K
< 1.4 for Ni2+ + HCO3
– NiHCO3
+, and log K
2
< 2 for NiCO3(aq) + CO3
2– Ni(CO3)2
2–, respectively. 相似文献
9.
Epoxy polymers with donor–acceptor type side groups were synthesized for application in nonlinear optics. The stability of the Pockels coefficient was measured in thin films after poling. The relaxation times and their temperature dependence seem to be correlated with dielectric measurements. Guest–host systems (polystyrene and polymethylmethacrylate with dimethylaminonitrostilbene) were investigated for comparison. 相似文献
10.
On the Dicyanothiocyanatomercurates(II) of the Alkaline-earth Metals The reactions between Hg(CN)2 and M(NCS)2 · nH2O (M = Mg, Ca, Sr, Ba; n = 3, 4) in aqueous solutions lead to the compounds M[Hg(CN)2SCN]2 · 4 H2O. The compounds yielded by crystallization are characterized with x-ray, spectroscopic, and thermal methods. The crystal structures of Mg[Hg(CN)2SCN]2 · 4 H2O and Sr[Hg(CN)2SCN]2 · 4 H2O have been determined by x-ray structure analysis. These structures can be compared with the compounds M′Hg(CN)2SCN (M′ = K, Rb, Cs). 相似文献