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Syn Arrangement (syn + arrangement)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Metal Ion Complementarity: Effect of Ring-Size Variation on the Conformation and Stability of Lead(II) and Cadmium(II) Complexes with Pendant-Armed Crowns

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2007
Martín Regueiro-Figueroa
Abstract The binding tendencies of the pendant-armed crown ethers L1,L3 [L1 = N,N, -bis(benzimidazol-2-ylmethyl)-1,7-diaza-12-crown-4, L2 = N,N, -bis(benzimidazol-2-ylmethyl)-1,10-diaza-15-crown-5) and L3 = N,N, -bis(benzimidazol-2-ylmethyl)-4,13-diaza-18-crown-6] towards PbII and CdII have been investigated. The X-ray crystal structure of [Cd(L3)](ClO4)2·EtOH shows that, in the solid state, the CdII ion is eight-coordinate and fits quite well into the crown hole, favouring an anti arrangement of the organic receptor. NMR measurements recorded in acetonitrile solution indicate that increasing the crown size induces a conformational change in the series of CdII complexes. The conformation goes from a syn arrangement for L1 to an anti arrangement for L3, passing through a syn [lrarr2] anti equilibrium in the complex derived from L2. On the contrary, no conformational change was observed for the corresponding PbII complexes, which have a syn conformation in all cases. These results have been confirmed by means of density functional theory (DFT) calculations performed by using the B3LYP model. The binding constants obtained from UV/Vis titration experiments in DMSO solution demonstrate that a decrease in the crown size provokes a 102 -fold enhancement of the stability for this series of CdII complexes, whereas for PbII a gradual decrease of the binding constants is observed. Receptor L1 shows a certain degree of selectivity for CdII over PbII, with a selectivity factor > 102. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

[,-4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene]bis[(trifluoroacetato)gold(I)] and its dichloromethane 0.58-solvate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Tünde Tunyogi
The dinuclear AuI complex containing the 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) ligand and trifluoroacetate anions exists in a solvent-free form, [,-4,5-bis(diphenylphosphino)-9,9-dimethylxanthene]bis[(trifluoroacetato)gold(I)], [Au2(C2F3O2)2(C39H32OP2)], (I), and as a dichloromethane solvate, [Au2(C2F3O2)2(C39H32OP2)]·0.58CH2Cl2, (II). The trifluoroacetate anions are coordinated to the AuI centres bridged by the xantphos ligand in both compounds. The AuI atoms are in distorted linear coordination environments in both compounds. The phosphine substituents are in a syn arrangement in the xantphos ligand, which facilitates the formation of short aurophilic Au...Au interactions of 2.8966,(8),Å in (I) and 2.9439,(6),Å in (II). [source]

{4,10-Bis[2-(2-oxidobenzylideneamino-,2N,O)benzyl]-1,7-dioxa-4,10-diazacyclododecane-,4O1,N4,O3,N10}ytterbium(III) perchlorate acetonitrile solvate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
Marina González-Lorenzo
In the crystal structure of the title compound, [Yb(C36H38N4O4)]ClO4·CH3CN, the ytterbium ion is eight-coordinated and deeply buried in the cavity of the dianionic Schiff base ligand. The coordination polyhedron may be described as a distorted square antiprism that shows a twist angle of 29.5,(1)° between the two square planes. The receptor adopts a syn arrangement, with both pendent arms on the same side of the crown group, and there are two helicities (one associated with this layout of the pendent arms and the other with the conformation of the crown ring), which give rise to enantiomeric pairs of diastereoisomers, viz. ,(,,,,) and ,(,,,,). [source]

4-(4-Chlorophenyl)-3-(4-phenylpent-4-enyloxy)-1,3-thiazole-2(3H)-thione

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2006
Hartmut Fuess
The title compound, C20H18ClNOS2, is a thiazole-derived thiohydroxamic acid O-ester. The value of Z, is 3 and the asymmetric unit comprises three molecules of identical helicity along the N,O bond. Two of these show an anti and the third a syn arrangement of substituents attached in positions 3 and 4 to the 1,3-thiazole nucleus. [source]