摘要:

AbstractThe geometries of molecules H3AXAH3(X=O, S, Se and A=C, Si) have been optimized using STO‐3Gab initiocalculations and gradient method and the results are in good agreement with reported experimental values. From the STO‐3G optimized geometries, we have also calculated the electronic structures of these molecules using 4–31G and 6–31G basis sets to obtain the MO energies, atomic net charges and dipole moments. The ionization potentials calculated by 6–31G basis set are in good agreement with experiment

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100101

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractCO hydrogenation on tungsten carbides has been investigated. The methanation activities of tungsten carbides are comparable to that of supported Group VIII metal catalysts. Temperature‐programmed thermal desorption spectra of CO on tungsten carbide show that CO is adsorbed non‐dissociatively, and the surface‐CO bond appears to be rather

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100102

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractElectrochemical oxidation of diphenylamine (DPA) in acetonitrile solution produced an adhesive conducting polydiphenylamine (PDPA) film on the electrode, which exhibited multiple colour variation in a wide range of potential. The polymer was characterized by cyclic voltammetry, FTIR and ESR. The results indicate that the electropolymerization of diphenylamine performs via the 4,4′ CC phenyl‐phenyl coupling mechanism. FTIR, ESR and conductivity measurements for the different states of PDPA show that polydiphenylamine can be reversibly doped and dedoped either chemically or electrochemically. It is evidenced also that there are paramagnetic species—polarons in PDPA supposed to be the current

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100103

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractK6CrNb15O42crystallizes in the hexagonal system witha=9.126 (3) Å,c=12.068(3) Å,V=870.4(5) Å2, and space groupP62/mcm, Z=1. The structure was solved using direct method and Fourier Techniques. Of the 829 unique reflections measured by counter techniques, 448 with1≥ 3σ(I) were used in the least‐squares refinement of the model toR=0.034 (Rw=0.044). The structure of K6CrNb15O42may be described as consisting of corner‐shared and edge‐shared octahedra, the ring units composed of six octahedra of Nb(1) are corner‐shared one another along thec‐axis to form hexagonal column octahedra chains which are connected by K+and oct

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100104

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractEight new complexes with the formula [PhC2C(OH)R1R2]Co2(CO)4were prepared from phenyl substituted propargylic alcohols and dicobalt octacarbonyl. The reactions of these propargylic alcohol complexes with active methylene compounds, 2,4‐pentanedione or ethyl acetoacetate, in the presence of an acid, HBF4(40%) + P2O5(in excess) or BF2·Et2O, at room temperature in dichloromethane were investigated. From the 1‐alkyl substituted tertiary propargylic alcohol complexes, three new conjugated ene‐yne complexes produced by intramolecular dehydration reaction were isolated in high yields (82–95%). On the other hand, four new alkylated complexes were obtained with satisfactory yields (44–66%) from the secondary propargylic alcohol complexes. The influence of other acids, phosphorus pentoxide and polyphosphoric acid, on both dehydration reaction and alkylated reaction was al

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100105

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractThe rate constants and equilibrium constants of ligand exchange reactions between bis (alkylxanthato)palladium(II), Pd (S2COR)2(R =Am,n‐Hex, Bz), and bis(N, N‐dialkyldithiocarbamato) palladium(II), Pd(S2CNR2)2(R =Et,n‐Pr,n‐Bu), in chloroform solution have been determined in a temperature range of 20–50°C by means of high‐performance liquid chromatography. It was found that both the forward and reverse reactions are of second order. All of the equilibrium constantsKdetermined are 10.3±1.0, much greater than the value (K=4) calculated statistically which indicates that the ternary complexes are more stable than the binary complexes. The experimental results revealed that the reaction rate decreases with the increase in the size of R and R1groups and the latter are more remarkable, consistent with the deduction of steric effect. The activation parameters of the reactions have been calculated. In reaction series (11) and (12) (in the text) the isokinetic temperatures β =390±8 K and β =346 ± 15 K have been observed respectively. A plausible mechanism involving an eight‐membered ring intermediate has been proposed on the basis of e

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100106

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractTitle compound,Mr=1273.16, was synthesized by a substitution reaction and its crystal is triclinic belonging to space groupP1with cell parameters:a=13.944(2),b=14.143(7),c=14.233(3) Å, α =77.35(3)°, β =69.94(2)°, γ =63.50(3)°,V=2351(1) Å3,Z=2,Dc=1.799g cm−2. Room temperature, graphite‐filtered Mo Kαradiation (λ =0.71073Å) was used for data collection. μ =14.988 cm−1,F(000) =1280,R=0.051 for 7025 observed reflections. The crystal consists of decrete cluster molecules containing a cluster core [Mo2(μ3‐S)]10+with three μ‐S, oneμ‐dtp(dtp =[S2P(OC2H5)]2‐), three χ‐dtp and one allylthioureo to form a local six‐coordinated sphere around each Mo atom. The bonds of cluster skeleton [Mo3(μ3‐S)(μ‐S)3]4+, MoMo 2.744∼2.766, Mo—(μ2‐S) 2.340∼2.342 and Mo—(μ‐S)2.272∼2.296 Å

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100107

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractEquilibrium constants for the binding of azide to ferri‐cytochromecat temperature range‐of 305–325 K were determined at pH =7 by using1H double resonance method. Thermodynamic values (ΔH°=‐34.5 kJ/mol,ΔS°=‐100 J/mol) were obtained from van't Hoff's relation and were compared with those for azide binding to other ferric hemeproteins. The reason of lower affinity of cytochromecfor azide

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100108

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractA new imidazolate bridged Cu2+, Zn2+binuclear complex [(dtma) CuImZn (dtma)]ClO4· 2.5H2O taken as active site model for Cu, Zn‐SOD has been synthesized and its crystal structure determined. All the bond lengths, bond angles and the distance between Cu and Zn atoms in Cu‐Im‐Zn core of the model complex are close to those in Cu, Zn‐SOD. ESR parameters of the model complex as a function of pH show that the imidazolate bridge is stable in pH range 10–12, and is broken on Zn side at pH ∼9. With decreasing pH, the imidazole is released at pH ∼4 and the dtma ligand dissociates from the Cu containing fragm

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100109

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY

摘要:

AbstractThe title compound was prepared by the reaction of Mo3S4(dtp)4(H2O) [dtp =S2P(OEt)2] with NaOAc·3H2O and C4H2NCS2NH4. Crystallographic data: [Mo3(μ‐S)(μ‐S)2(μ‐OAc)‐(S2CNC4H2)3(O)2] · 0.5CH2Cl2· 2H2O,Mr=980.18, triclinic, space groupP1,a=12.360(3),b=16.653(6),c=9.206(2) Å, α =101.97(2), β =108.32 (2), γ =86.14(3)°.V=1759.6(9)Å2,Z=2,Dc=1.85 g/cm2, F(000) =962, μ(Mo Kα) =16.53 cm−1. FinalR=0.044 for 4301 reflections withI>3σ (I). This compound may be regarded as a mixed‐valent trinuclear molybdenum cluster {Mo3(V) Mo(V) (μ2‐S) (μ‐S)2‐(μ‐OAc) (S2CNC4H8)3(O)2}. The Mo—Mo distances are 2.783(1), 2.833(1) and 3.374(2)Å in the Mo3non‐equilateral triangle and there exist only two Mo—Mo bonds. The cluster was obtained by oxidation and ligand substitution of {Mo2(

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100110

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1992

数据来源: WILEY