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571.
Cadierno V Díez J García-Alvarez J Gimeno J Nebra N Rubio-García J 《Dalton transactions (Cambridge, England : 2003)》2006,(47):5593-5604
Reactions of [PdCl2(COD)] with 1 equiv. of the iminophosphorane-phosphine ligands Ph2PCH2P{=NP(=O)(OR)2}Ph2 (R=Et, Ph) lead to the novel Pd(II) derivatives cis-[PdCl2(kappa2-(P,N)-Ph2PCH2P{=NP(=O)(OR)2}Ph2)] (R=Et, Ph). Pd-N bond cleavage readily takes place upon treatment of these species with a variety of two-electron donor ligands. By this way, complexes cis-[PdCl2(kappa1-(P)-Ph2PCH2P{=NP(=O)(OR)2}Ph2)(L)] (R=Et, L=CNtBu, CN-2,6-C6H3Me2, py, P(OMe)3, P(OEt)3; R=Ph, L=CNtBu, CN-2,6-C6H3Me2, py, P(OMe)3, P(OEt)3) have been synthesized in high yields. The addition of two equivalents of ligands to dichloromethane solutions of [PdCl2(COD)] results in the formation of complexes trans-[PdCl2(kappa1-(P)-Ph2PCH2P{=NP(=O)(OR)2}Ph2)2] (R=Et, Ph), which can be converted into the dicationic species [Pd(Ph2PCH2P{=NP(=O)(OR)2}Ph2)2][SbF6]2 (R=Et, Ph) by treatment with AgSbF6. Complex also reacts with CNtBu to afford trans-[Pd(kappa1(P)-Ph2PCH2P{=NP(=O)(OPh)2}Ph2)2(CNtBu)2][SbF6]2. The structures of and have been determined by single-crystal X-ray diffraction methods. In addition, the ability of these Pd(II) complexes to promote the catalytic cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been studied. 相似文献
572.
Andrew M. Romine Dr. Noel Nebra Andrey I. Konovalov Dr. Eddy Martin Dr. Jordi Benet‐Buchholz Prof. Vladimir V. Grushin 《Angewandte Chemie (International ed. in English)》2015,54(9):2745-2749
CuCl or pre‐generated CuCF3 reacts with CF3SiMe3/KF in DMF in air to give [Cu(CF3)4]? quantitatively. [PPN]+, [Me4N]+, [Bu4N]+, [PhCH2NEt3]+, and [Ph4P]+ salts of [Cu(CF3)4]? were prepared and isolated spectroscopically and analytically pure in 82–99 % yield. X‐ray structures of the [PPN]+, [Me4N]+, [Bu4N]+, and [Ph4P]+ salts were determined. A new synthetic strategy with [Cu(CF3)4]? was demonstrated, involving the removal of one CF3? from the Cu atom in the presence of an incoming ligand. A novel CuIII complex [(bpy)Cu(CF3)3] was thus prepared and fully characterized, including by single‐crystal X‐ray diffraction. The bpy complex is highly fluxional in solution, the barrier to degenerate isomerization being only 2.3 kcal mol?1. An NPA study reveals a huge difference in the charge on the Cu atom in [Cu(CR3)4]? for R=F (+0.19) and R=H (+0.46), suggesting a higher electron density on Cu in the fluorinated complex. 相似文献
573.
Hanim Kim Yun Ho Kim Sunhee Lee David M. Walba Noel A. Clark Sang Bok Lee 《Liquid crystals》2013,40(3):328-341
Bent-core smectic liquid crystal (LC) phases (B phases) have been widely studied since their unusual polar and chiral properties were discovered in the 1990s. Relatively few studies have examined the mechanisms by which the orientation of the B phase may be controlled to produce the type of macroscopic domain that is essential for organic semiconductor, optical device and patterning applications. This review is intended to cover recent progress towards controlling the B phases upon layering, including anisotropic treatment methods and topographical confinement methods. Finally, this review closes with a discussion of B smectic phases that have been fabricated for use in certain applications. 相似文献
574.
Richard C. Brewster Jae-Baek Lee Benjamin Moore Jonathan A. Noel Mark Siggers 《Journal of Graph Theory》2020,94(3):398-420
We say that a graph strongly arrows a pair of graphs and write if any coloring of its edges with red and blue leads to either a red or a blue appearing as induced subgraphs of . The induced Ramsey number, , is defined as . We consider the connection between the induced Ramsey number for a pair of two connected graphs and the induced Ramsey number for multiple copies of these graphs , where denotes the pairwise vertex-disjoint union of copies of . It is easy to see that if , then . This implies that For several specific graphs, such as a path on three vertices vs a complete multipartite graph, a matching vs a complete graph, or a matching vs another matching, it is known that the above inequality is tight. On the other hand, the inequality is also strict for some graphs. However, even in the simplest case when is an edge and , it is not known for what and for what the above inequality is tight. We show that it is tight if is connected and is at least as large as the order of . In addition, we make further progress in determining induced Ramsey numbers for multiple copies of graphs, such as paths and triangles. 相似文献
575.
We construct a CAT(0) group containing a finitely presented subgroup with infinitely many conjugacy classes of finite-order
elements. Unlike previous examples (which were based on right-angled Artin groups) our ambient CAT(0) group does not contain
any rank 3 free abelian subgroups. We also construct examples of groups of type F
n
inside mapping class groups, Aut(), and Out() which have infinitely many conjugacy classes of finite-order elements.
相似文献