Home About us Contact | |||
Starting Complexes (starting + complex)
Selected AbstractsDynamic Equilibria in Solvent-Mediated Anion, Cation and Ligand Exchange in Transition-Metal Coordination Polymers: Solid-State Transfer or Recrystallisation?CHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2009Xianjin Cui Abstract The solution properties of a series of transition-metal,ligand coordination polymers [ML(X)n], [M=AgI, ZnII, HgII and CdII; L=4,4,-bipyridine (4,4,-bipy), pyrazine (pyz), 3,4,-bipyridine (3,4,-bipy), 4-(10-(pyridin-4-yl)anthracen-9-yl)pyridine (anbp); X=NO3,, CH3COO,, CF3SO3,, Cl,, BF4,; n=1 or 2] in the presence of competing anions, metal cations and ligands have been investigated systematically. Providing that the solubility of the starting complex is sufficiently high, all the components of the coordination polymer, namely the anion, the cation and the ligand, can be exchanged on contact with a solution phase of a competing component. The solubility of coordination polymers is a key factor in the analysis of their reactivity and this solubility depends strongly on the physical properties of the solvent and on its ability to bind metal cations constituting the backbone of the coordination polymer. The degree of reversibility of these solvent-induced anion-exchange transformations is determined by the ratio of the solubility product constants for the starting and resultant complexes, which in turn depend upon the choice of solvent and the temperature. The extent of anion exchange is controlled effectively by the ratio of the concentrations of incoming ions to outgoing ions in the liquid phase and the solvation of various constituent components comprising the coordination polymer. These observations can be rationalised in terms of a dynamic equilibrium of ion exchange reactions coupled with Ostwald ripening of crystalline products. The single-crystal X-ray structures of [Ag(pyz)ClO4], (1), {[Ag(4,4,-bipy)(CF3SO3)],CH3CN}, (2), {[Ag(4,4,-bipy)(CH3CN)]ClO4, 0.5,CH3CN}, (3), metal-free anbp (4), [Ag(anbp)NO3(H2O)], (5), {[Cd(4,4,-bipy)2(H2O)2](NO3)2,4,H2O}, (6) and {[Zn(4,4,-bipy)SO4(H2O)3] ,2,H2O}, (7) are reported. [source] The Reductive Elimination of Methane from ansa -Hydrido(methyl)metallocenes of Molybdenum and Tungsten: Application of Hammond's Postulate to Two-State ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2005José-Luis Carreón-Macedo Abstract The energetic profile of the methane reductive elimination from a selected number of hydrido(methyl)molybdenocene and -tungstenocene derivatives has been calculated by DFT methods. The calculations were carried out for the CH2(C5H4)2M (a -M), SiH2(C5H4)2M (a -H2Si,M), and SiMe2(C5Me4)2M (a -Me2Si,M*) ansa -metallocene systems for M = Mo, W. They include the full optimization of minima [the hydrido(methyl) starting complexes, M(H)(CH3), the intermediate methane complexes, M(CH4), and the metallocene products in the singlet and triplet configurations, (3M and 1M)], transition states (for the methyl hydride reductive elimination, M,TSins, and for the hydrogen exchange, M,TSexch), and the minimum energy crossing point (M,MECP) leading from the singlet methane complexes to the corresponding triplet metallocenes. The results are compared with those previously obtained for the simpler (C5H5)2M (Cp2M) systems (J. C. Green, J. N. Harvey, and R. Poli, J. Chem. Soc., Dalton Trans.2002, 1861). The calculated energy profiles, notably the relative energies of M,TSins and M,MECP, are in agreement with available experimental observations for the a -Me2Si,M* systems. The comparison of the energies and geometries of the rate-determining M,TSins and M,MECP structures with those of the thermodynamically relevant minima for the various systems show the applicability of Hammond's postulate to two-state reactions. However, one notable exception serves to show that the principle is only quantitatively reliable when all the potential energy surfaces for the set of analogous reactions have similar shapes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis, characterization, electrochemical, catalytic and antimicrobial activity studies of hydrazone Schiff base ruthenium(II) complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2010N. Thilagavathi Abstract Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh3)2B] in benzene, where E = P or As; B = PPh3 or AsPh3 or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT-IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl,aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro-organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd. [source] Stereoselective Functionalization of 2-(1-Aminoalkyl)aziridines via Lithiation of Aziridine,Borane ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2005José M. Concellón Prof. Dr. Abstract Highly selective functionalization of the aziridine ring of (2S,1,S)-2-(1,-aminoalkyl)aziridines 1, through successive formation of aziridine,borane complexes, lithiation, treatment with a variety of electrophiles and final decomplexation is described. The influence of the structure of the starting complexes 2 and of the electrophiles in the stereoselectivity of this process has been studied. Finally, successive double lithiation,electrophile reactions were carried out affording enantiopure 1,2,3,3-tetrasubstituted aziridine,borane complexes with high selectivity. Se describe la funcionalización altamente selectiva de (2S,1,S)-2-(1,-aminoalquil)aziridinas 1 a través de un proceso de formación de complejos borano,aziridina, litiación, tratamiento con electrófilos y descomplejación. También ha sido objeto de estudio la influencia de la estructura de los complejos 2 y de los electrófilos en el proceso. Finalmente, se ha llevado a cabo una doble reacción litiación y reacción con electrófilos dando lugar a complejos borano,aziridina 1,2,3,3-tetrasustituidas de forma enantiopura y con alta selectividad. [source] |