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Relevant academic research and scientific papers

Lead(ii) tetrafluoroborate and hexafluorophosphate complexes with crown ethers, mixed O/S- and O/Se-donor macrocycles and unusual [BF4] - and [PF6]- coordination

The reaction of Pb[BF4]2 in H2O/MeCN solution with the macrocycle 18-crown-6 gave the dinuclear complex [{Pb(18-crown-6)(H2O)(μ2-BF4)} 2][BF4]2, containing two nine-coordinate lead centres, each bound to all six oxygens of a crown ligand, one water molecule and bridged by two μ2-BF4 groups. In contrast, the oxa-thia crown [18]aneO4S2 gave the mononuclear [Pb([18]aneO4S2)(H2O)2(BF 4)][BF4] in which the lead is coordinated O 4S2 within the puckered ring of the macrocycle, and with two water molecules on one side of the plane and a chelating (κ2) BF4- on the other. The [Pb([18]aneO4Se2)(BF4)2] has the two BF4- groups arranged mutually cis and with the macrocycle folded; within each BF4- group the Pb-F distances differ by ～0.5 A, producing a very unsymmetrical chelate. The 15-membered ring macrocycles 15-crown-5 and [15]aneO3S2 produce sandwich complexes [Pb(macrocycle)2][BF4]2 which contain 10-coordinate lead centres. Pb[PF6]2 in H2O/MeCN solution formed [Pb(18-crown-6)(H2O) 2(PF6)][PF6] and [Pb([18]aneO4S 2)(H2O)2(PF6)][PF6] which contain weak κ2-coordination of the PF6- group on the opposite side of the macrocyclic ring to two coordinated water molecules, giving 10-coordinate lead. In contrast, [Pb([18]aneO 4Se2)(PF6)2] has two κ2-coordinated PF6- groups disposed cis, with a very folded macrocycle conformation. In [Pb(18-crown-6)(NO 3)(PF6)] a chelating nitrate group occupies the coordination sites at Pb(ii) instead of the two water molecules, and the weakly coordinating PF6- group is tridentate. The crystal structures of the lead nitrate complexes, [Pb(15-crown-5)(NO3) 2] and [Pb([18]aneO4Se2)(NO3) 2], containing nine- and 10-coordinate lead respectively, are also reported. In solution the complexes are labile, and both conductivity and 19F NMR spectroscopic studies show the BF4- and PF6- groups are dissociated, whereas in the nitrate complexes the anion coordination is retained in solution. The identification of the coordination modes of the NO3- and BF4 - groups in the solid complexes by IR spectroscopy is discussed. The Royal Society of Chemistry 2013.

Synthesis of Oxygen and Sulphur Containing Crown Compounds under Solid-Liquid Phase Transfer Catalysis

Sulphur containing crown compounds and podands have been synthesized by intermolecular nucleophilic displacements of tosylates with thiolate ions generated in situ under solid-liquid phase transfer catalysis.

Synthesis and Properties of Some Lanthanoid(III) Perchlorates with Macrocyclic Polythioethers of the -Crown-6 Type. Crystal Structure of Aquadiperchlorato(1,4,10,13-tetraoxa-7,16-dithiacyclo-octadecane)lanthanum(III) Perchlorate

Some complexes of lanthanoid(III) perchlorates have been prepared with three polythia macrocycles of the -crown-6 type.By using the ligand 1,4,10,13-tetraoxa-7,16-dithiacyclo-octadecane, L1, in methyl cyanide,three series of complexes have been obtained with formulae (i) Ln3*L1*H2O (Ln=La, Ce, or Pr) (ii) Ln3*L1*H2O*xMeCN (Ln=Ce, Pr, Nd, Sm, Eu, Ho, or Yb; x=1.5 or 2), and (iii) Nd3*L1.The crystal and molecular structure of the title complex has been determined by X-ray diffractometric data.The structure has been refined by least-squares techniques to R=0.036 for 4635 observed reflections.The lanthanum(III) ion is ten-co-ordinated to the six donor atoms of L1, to two oxygen atoms of a (1-) ion, to an oxygen atom of a second (1-), and to an oxygen atom of a water molecule.The co-ordination polyhedron can be described as a decatetrahedron.The macrocycles 1,10-dioxa-4,7,13,16-tetrathiacyclo-octadecane, L2, and 1,4,7,10,13,16-hexathiacyclo-octadecane, L3, do not co-ordinate to lanthanoid(III) perchlorates in methyl cyanide but in dichloromethane the complexes Eu3*L2*H2O and Ln3*L3*H2O (Ln=Sm, Eu, or Yb) can be isolated.The i.r. and electronic spectra of all the complexes are discussed.The electron-transfer transitions are consistent with an optical electronegativity value of 2.8 for ligand L1 and 2.7 for L2 and L3.