- The catalytic synthesis of thiacrowns from thiiranes by Group VI and VII transition metal carbonyl complexes
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The synthesis of thiacrowns by the catalytic ring opening cyclooligomerization of thiirane has been investigated by using some Group VI and Group VII metal carbonyl complexes. The Group VI catalyst precursors were transition metal complexes of the form M(
- Adams, Richard D.,Brosius, Kellie M.,Kwon, O.-Sung
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- SYNTHESIS OF 15- AND 18-MEMBERED POLYTHIAMACROCYCLIC LIGANDS
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Reaction of 1,8-dimercapto-3,6-dithioactane with oxa-, aza-. and thiadihaloderivatives under high dilution conditions in the presence of cesium carbonate, which acts as a template for the condensation reaction, produces 15- and 18-membered polythiamacrocyclic ligands in yields greater than 50percent.
- Pavlishchuk, V. V.,Strizhak, P. E.
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p. 553 - 555
(2007/10/02)
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- Crown Thioether Chemistry: Structural and Conformational Studies of Tetrathia-12-crown-4, Pentathia-15-crown-5, and Hexathia-18-crown-6. Implications for Ligand Design
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Tetrathia-12-crown-4 (12S4) in the solid state adopts a square conformation with the sulfur atoms at the corners, to yield a structure derived from fusion at the terminal S atoms of two "bracket" units. This macrocycle crystallizes in the monoclinic system, space group Cc, with a = 13.028(7) Angstroem, b = 12.884(5) Angstroem, c = 14.493(7), (β = 108.18(4) deg, and Z = 8.Pentathia-15-crown-5 (15S5) assumes an irregular conformation generated from two bracket units by fusion at one S atom and connection of the remaining two terminal S atoms by a -CH2CH2- linkage.This crown thioether also crystallizes in the monoclinic system, space group P21/n, with a = 16.444(3) Angstroem, b = 5.432(1) Angstroem, c = 18.255(3) Angstroem, β = 115.58(1) deg, and Z = 4.Hexathia-18-crown-6 (18S6) adopts a conformation produced by connection of two bracket units by two -CH2CH2- linkages.It crystallizes in the orthorhombic system, space group Fdd/2, with a = 20.466(1) Angstroem, b = 32.222(3) Angstroem, c = 5.213(4) Angstroem, and Z = 8.Analysis of these structures reveals a pronounced preference for gauche placement at C-S bonds.This preference causes the ubiquity of bracket units and contrasts with the antipathy to gauche placement of the C-O bonds in oxa-crown ethers.This marked difference derives from the difference in C-E bond lenghts, which changes nonbonded 1,4-interactions in both C-C-E-C and E-C-C-E fragments.
- Wolf, Robert E.,Hartman, JudithAnn R.,Storey, John M. E.,Foxman, Bruce M.,Cooper, Stephen R.
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p. 4328 - 4335
(2007/10/02)
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- 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
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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.
- Ciampolini, Mario,Mealli, Carlo,Nardi, Nicoletta
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p. 376 - 382
(2007/10/02)
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