Summary. A series of novel tridentate ligands with nitrogen and oxygen donor sites was synthesized starting from enantiomerically
pure (S)- and (R)-1-(pyridin-2-yl)ethylamine, the preparation and resolution of which was developed. The new optically active ligands were
tested as in situ catalysts together with Ru(PPh3)3Cl2 in the enantioselective transfer hydrogenation of acetophenone with isopropanol. The secondary amine ligand (S)-2,4-di-tert-butyl-6-(1-(pyridin-2-yl)ethylamino)methylphenol gave the best results with almost quantitative conversion and 47%ee.
Received August 17, 2001. Accepted August 27, 2001 相似文献
We derive results on the interpolation of complete quasinormed operator ideals, mainly for the absolutelyp-summing and thes-number idealsSps
defined by Pietsch. By estimating theK-Functional of Peetre, we get that the interpolation ideal (Sp1s
,Sp2s
),,p is contained inSps
and is even equal to it in the case of the approximation numbers. A similar fact is proved for absolutely (p, q)-summing operators, interpolating the first index. We show further that the absolutelyp-summing operators onc0 are contained in the complex interpolation space (p1(co), p2(co))[].The previous results are then applied to prove summability properties for the eigenvalues of operators in Banach spaces, which are products ofSp1s
-type and absolutelypj-summing operators. Roughly speaking, the summability order is the harmonic sum of thepi- andpj-indices, wherepj2. In the case of Hilbert spaces, this reduces to the well-known Weyl-inequality. The method uses an abstract interpolation estimate for ideal quasinorms which may be useful also for other operator ideals. 相似文献
Let Ω ? N be an open set with and some l > 0 satisfying an additional regularity condition. We give asymptotic estimates for the approximation numbers αn of Sobolev imbeddings over these quasibounded domains Ω. Here denotes the Sobolev space obtained by completing under the usual Sobolev norm. We prove , where . There are quasibounded domains of this type where γ is the exact order of decay, in the case p ? q under the additional assumption that either 1 ? p ? q ? 2 or 2 ? p ? q ? ∞. This generalizes the known results for bounded domains which correspond to l = ∞. Similar results are indicated for the Kolmogorov and Gelfand numbers of Ip,qm. As an application we give the rate of growth of the eigenvalues of certain elliptic differential operators with Dirichlet boundary conditions in , where Ω is a quasibounded domain of the above type. 相似文献
The novel complexes CpFe(CO)(COR)P(C6H5)2NR'R* with Cp = C5H5,C9H7 (indenyl); R = CH3, C2H5, CH(CH3)2, CH2C6H5;R` = H, CH3, C2H5, CH2C6H5 and R* = (S)-CH(CH3)(C6H5), have been synthesized by reaction of CpFe(CO)2R wiht P(C6H5)2NR`R* and characterized analytically as well as spectroscopically. The pairs of diastereoisomers RS/SS have been separated by preparative liquid chromatography and fractional crystallization, respectively. The optically pure complexes (+)436- und ()436-CpFe(CO)(COR)P(C6H5)2NR`R* are configurationally stable at room temperature. At higher temperatures they equilibrate with CpFe(CO)2R and epimerize with respect to the Fe configuration. 相似文献
The newly adjusted energy-consistent nine-valence-electron pseudopotentials for K to Fr are used to calculate spectroscopic properties for the neutral and positively charged alkali dimers using coupled cluster and density functional theory. For the neutral dimers the static dipole polarizability was calculated. The coupled cluster results are all in excellent agreement with experimental values. The density functionals used can give quite different spectroscopic properties especially for the dipole polarizability, with the Perdew-Wang PW91 functional performing best. 相似文献
C7H7Mo(CO)(PN★)I (I) (PN★ (S)(+)-(C6H5)2PN(CH3)CH(CH3)(C6H5)) is prepared in 90% yield by reaction of C7H7Mo(CO)2I and PN★. The two diastereo-isomers Ia and Ib differing only in the Mo-configuration exhibit chemical shift differences of their C7H7 and CH3 signals. Ia and Ib can be separated by fractional crystallization. In solution Ia epimerizes with respect to the Mo configuration. The half lives in benzene for the equilibration Ia ? Ib are 5.5, 30, and 104 min at 60, 50, and 40°C, respectively. Phosphine exchange experiments show that the epimerization proceeds via PN★ dissociation.An X-ray structure analysis was carried out on a single crystal of Ia. The absolute configuration at Mo was determined to be (R). 相似文献
Zusammenfassung Es werden molekulare Struktur, Energie des Grundzustandes, Bindungsabstände, Bindungsenergie, Ionisierungsenergie und Protonenaffinität der Siliziumwasserstoffverbindungen SiHn, SiHn+ und SiHn– (n=3, 4 oder 5) nach der Einzentrenmethode berechnet.
OCE-calculations on some silicon hydrides of the type SiH n, SiH
n+
and SiH
n–
OCE-Calculations are reported for molecular structures, ground state energies, bond distances, binding energies, ionization potentials and proton affinities of the silicon hydrides SiHn, SiHn+ and SiHn– (n=3, 4 or 5).
Résumé Calcul par la méthode monocentrique de la structure moléculaire, de l'énergie de l'état fondamental, des longueurs de liaison, des énergies de liaison, des potentiels d'ionisation et des affinités protoniques pour les hydrures de silicium SiHn, SiHn+ et SiHn– (n=3, 4 ou 5).
This paper deals with the Neumann problem of the pre-Maxwell partial differential equations for a vector field v defined in a region G ? R 3. We approximate its uniquely determined solution (integrability conditions assumed) uniformly on G by explicitly computable particular integrals and linear combinations of vector fields with a “fundamental” sequence of points . 相似文献
In the following work we present an uniform theory for proofs of theorems on local and numerably local properties of spaces and maps (over B). As applications of our two main theorems, we obtain some new results, but also theorems proven by A. Dold [3] and T. tom Dieck [2], and well-known theorems on CW-spaces. 相似文献