Synthesis and reactivity of a bis(disulfide)-bridged RuMo3S4 double-cubane cluster: a new family of nona- or decanuclear mixed-metal sulfide clusters with two RuMo3S4 units

A bis(disulfide)-bridged RuMo3S4 double-cubane cluster [{(Cp*Mo)3(mu3-S)4Ru}(mu2-eta2:eta1-S2)]2[PF6]2 (2, Cp* = eta5-C5Me5) is readily available from cluster [(Cp*Mo)3(mu3-S)4RuH2(PPh3)][PF6] (1) and S8. The reactions of cluster 2 with [M(PPh3)4] (M = Pd, Pt) give rise to the formation of a new family of nona- or decanuclear mixed-metal sulfide clusters, [{(Cp*Mo)3(mu3-S)4Ru}2(mu3-S)2{Pd(S)(PPh3)}][PF6]2 (3), [{(Cp*Mo)3(mu3-S)4Ru}2(mu3-S)2{(Pd(PPh3))2(mu2-S)}][PF6]2 (4), and [{(Cp*Mo)3(mu3-S)4Ru}2(mu3-S)2{Pt(PPh3)2}][PF6]2 (5), with two RuMo3S4 cubane units, the structures of which have been determined by X-ray diffraction studies.     

Symmetry in the vanishing of Ext over stably symmetric algebras

A Frobenius algebra over a field k is called symmetric if the Nakayama automorphism is an inner automorphism. A stably symmetric algebra is defined to be a generalization of a symmetric k-algebra. In this paper we will study symmetry in the vanishing of Ext for such algebras R, namely, for all finitely generated R-modules M and N, for all i0 if and only if for all i0. We show that a certain class of noetherian stably symmetric Gorenstein algebras, such as the group algebra of a finite group and the exterior algebra Λ(kⁿ) when n is odd, have this symmetry using Serre duality. We also show that every exterior algebra Λ(kⁿ), whether n is even or odd, has this symmetry for graded modules using Koszul duality.     

CO_2在Fe-Zn-M/HY复合催化剂上加氢合成异丁烷的研究(英文)

对ＣＯ_２在Ｆｅ－Ｚｎ－Ｍ（Ｍ＝Ｚｒ,Ａｌ,Ｇａ和Ｃｒ）／ＨＹ复合催化剂上的加氢反应进行了研究。通过对复合催化剂的配比、反应温度以及气体空速的考察,确定了由ＣＯ_２加氢合成异丁烷的最佳反应条件。在对反应机理研究后发现,ＣＯ_２在复合催化剂上的加氢反应是一个混合了甲醇合成和甲醇制汽油（ＭＴＧ）的反应过程,而不是传统的ＦＴ反应过程。实验结果指出,反应中生成的烯烃是产生异丁烷的重要中间产物。在所有的催化剂上,异丁烷的组成在烃类中是最高的。在Ｈ２／ＣＯ２＝３,５ Ｍｐａ, ３０００ｈ~（－１）及３６０℃的反应条件下, ＣＯ_２在Ｆｅ－Ｚｎ－Ｚｒ／ＨＹ复合催化剂上进行加氢反应时,异丁烷在烃类中的选择性高达３８％,异丁烷的时空产率可达３．０ Ｃ－ｍｏｌ％,这是迄今为止我们所知由ＣＯ_２加氢合成异丁烷所得的最好结果。     

Oxidative polymerization of p-alkylphenols catalyzed by horseradish peroxidase

Enzymatic oxidative polymerization of p-alkylphenols using horseradish peroxidase as catalyst has been carried out in two polymerization solvent systems: a mixture of phosphate buffer (pH 7) and 1,4-dioxane, and a reverse micellar solution, yielding powdery polymeric materials. The polymer yield was much dependent upon the type of alkyl group in the monomer as well as the solvent type. In case of the polymerization of umbranched alkylphenols in the aqueous 1,4-dioxane, the polymer yield increased with increasing chain length of the alkyl group from 1 to 5, and the yield of the polymer from hexyl or heptylphenol was almost the same as that of the pentyl derivative. The relationship between the type of substituent and the polymer yield in the reverse micellar system was different from that in the aqueous 1,4-dioxane; the highest yield was achieved from ethylphenol. The resulting polymers had molecular weight of several thousands. The polymer was estimated to be composed from a mixture of phenylene and oxyphenylene units from IR analyses. TG measurement exhibited that the polymer had relatively high thermal stability. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1453–1459, 1997     

Novel Catalytic Hydrogenolysis of Trimethylsilyl Enol Ethers by the Use of an Acidic Ruthenium Dihydrogen Complex

The heterolytic cleavage of H ₂ is the key to the novel catalytic hydrogenolysis of trimethylsilyl enol ethers catalyzed by [RuCl(η²-H₂)(dppe)₂]OTf (dppe = 1,2-bis(diphenylphosphanyl)ethane, OTf = trifluoromethanesulfonate), which results in the formation of a ketone and Me₃SiH (see scheme). In addition, the stoichiometric, ruthenium-assisted protonation of a prochiral lithium enolate with H₂ gave a chiral ketone with high enantioselectivity (up to 75 % ee).     

Studies of cyclodextrin effect for glycosylation by galactosyltransferase

Cyclodextrins (CDs) do not disturb HPLC purification and do not form lather, which makes them superior to commonly used surfactants. In this paper, the authors describe the utility of CDs, specifically α-CD, β-CD, and γ-CD, for the synthesis of neoglycolipids from insoluble peptide-linked substrates. γ-CD was found to be well matched to the bulky benzyl group and accelerated the reaction for the substrate having Phe (F), while β-CD was well matched to the methyl group and accelerated the reaction for the substrate having Ala (A). Galactosylation to water-insoluble peptide-linked glucosaminide substrate by galactosyltransferase proceeded 63% at the most, but using either β-CD or γ-CD gave quantitative yield within 10 h.