Ruth-Maria Olk

The coordination chemistry of 1,3-dithiole-2-thione-4,5-dithiolate (dmit) and isologs

Abstract The 1,3-dithiole-2-thione-4,5-dithiolate (dmit) ligand and chalcogen atom substituted isologs have been extensively used in organic and coordination chemistry since their first reported synthesis in 1975. Over approximately the past 8 years a number of diverse and interesting dmit coordination complexes have been described. Also, dmit and isologs have been used in a variety of material applications, including in superconducting charge-transfer and radical anion salts. The synthesis, structures and properties of a selection of these compounds will be presented and discussed covering the literature from 1991 to approximately mid-1998.

In(III), Tl(III) and V(IV) tris-chelates of the heterocyclic dithiolene and diselenolene ligands 1,3-dithiole-2-thione-4,5-dithiolate (dmit), 1,2-dithiole-3-thione-4,5-dithiolate (dmt) and 1,3-diselenole-2-selone-4,5-diselenolate (dsis). Crystal and molecular structure of (Bu4N)2 [V(dmt)3]

Abstract Synthesis and characterization of the first trischelates of the dichalcogenolene ligands 1,3-dithiole-2-thione-4,5-dithiolate (dmit), 1,2-dithiole-3-thione-4,5-dithiolate (dmt)and 1,3-diselenole-2-selone-4,5-diselenolate (dsis) with the central ions In(III), Tl(III) and V(IV) are reported. On (Bu4N)2[V(dmt)3] the first X-ray structure of a dithiolene tris-chelate containing unsymmetric ligand was carried out: the compound crystallizes monoclinic, space group P21/c, with four molecules in the unit cell; a = 16.264(3), b = 17.319(4), c = 21.554(4) A, β = 103.03(2)°. The ligand dmt causes a very low symmetry of the VS6 moiety in [V(dmt)3]2− having pseudo-meridional arrangement of the three ligands. The EPR parameters of the compounds (Bu4N)2[V(dmit)3] and (Bu4N)2[V(dmt)3] measured in liquid and frozen acetonic solution are compared with those of the tris(maleonitriledithiolato)vanadate(IV) anion supporting a geometry of the anion being between octahedral and trigonal prismatic.

Synthesis of Stable Sources for 1,2-Diselenolate Dianion Chemistry : Bis (2-Selenoxo-1,3-Diselenole-4,5-diselenolato) zincate (II) and 4,5-Benzoylseleno-1,3-diselenole-2-selenone

Abstract The synthesis of 4,5-benzoylseleno-1,3-diselenole-2-selenone via bis (2-selenoxo-1,3-diselenole-4,5-di-selenolato) zincate (II) as a precursor for selenium ligands and selenium heterocycles is described.

A single-crystal electron paramagnetic resonance, 13C and 1H electron nuclear double resonance study of tetra-n-butylammonium-bis(1,2-dicyanoethylene-1,2-dithiolato)aurate(II), [(n-C4H9)4N]2[AuII(mnt)2]

A single-crystal electron paramagnetic resonance-electron nuclear double resonance study of 13C enriched tetra-n-butylammonium-bist(1,2-dicyanoethylene-1,2-dithiolato)aurate(II), [(n-C4H9)4N]2[AuII(S2C2(13CN)2)2]. diluted diamagnatically in the diamagnetic NiII complex, is reported. The spin density on the enriched C atoms was found to be nearly 1%. Extended Huckel theory molecular orbital calculations on the title complex confirm the magnitude of the 13C coupling and allow us to draw conclusions about the overall spin-density distribution.

Syntheses and Crystal Structures of Coinage Metal Thioether-Thiolato Complexes

Copper(I), silver(I), and two gold(I) complexes of the type (Ph3P)nM(L) [n = 1, 2, 3; L = 4-(methylthio)-2-thioxo-1,3-dithiole-5-thiolate (La), 1,2-dicyano-1-(methylthio)ethene-2-thiolate (Lb)] have been synthesized. The molecular structure of these complexes was determined by X-ray crystallography and shows differences in the coordinated sulfur atoms as well as in the coordination geometry of these (Ph3P)nM(L) complexes. In (Ph3P)2Cu(L) (2), the thioether thiolate ligands act as bidentate ligands, whereas in the silver and gold complexes (Ph3P)3Ag(L) (3) and (Ph3P)2Au(L) (4), only the thiolate sulfur is coordinated. Dissociation of one of the phosphane ligands of (Ph3P)2Au(La) (4a) occurs in boiling acetone and a linear two-coordinate gold(I) center is obtained, (Ph3P)Au(La) (5a).

Voltammetric characterisation of an insoluble tetrathiafulvalene derivative by means of modified carbon paste electrode

Abstract An insoluble tetrathiafulvalene (TTF) derivative is voltammetrically characterised by means of a carbon paste electrode in acetonitrile as solvent. The electrode is modified with the TTF derivative by adding a certain amount to the carbon paste. For the modification of the electrode an amount of about 4 × 10−7 moles of the TTF derivative (only 0.5% with respect to the mass of the carbon paste) is necessary. After the initial oxidation of the modified electrode the characteristic voltammograms of TTF with two oxidation peaks and two corresponding reduction peaks are observed. The influence of anodic treatment is studied and the voltammetric behaviour during the initial oxidation is discussed. The TTF derivative is able to mediate oxidations as shown by the reaction of bromide at the modified electrode.

Ligand exchange reactions between metal(II) chelates of different sulfur and selenium containing ligands IX. Exchange behavior of chelates of 1,3-Dithiole-2-thione-4,5-dithiolate (dmit) and 1,1-Dichalcogenolates. X-ray Structure of Bu4N[Zn(dmit)(Et2dtc)]

Abstract Nickel, copper and zinc bis-chelates of 1,3- dithiole-2-thione-4,5-dithiolate react with diethyldithio-, -thioseleno-, and diseleno-carbamates of these metals in acetone forming the mixed ligand complexes [M(dmit)(XYCNEt2)]− (X=Y=S or Se; X=S, Y=Se) exclusively which can be isolated purely as salts of suitable cations. This synthesis can be extended to mixed ligand systems containing other geminal ligands demonstrated by (Bu4N)2 [Ni(dmit)- (i-mnt)] (i-mnt=1,1-dicyanoethene-2,2-dithiolate). EPR measurements on the copper compounds and 1H, 13C and 77Se NMR measurements on the nickel and zinc systems as well show that the four- membered chelate ring gains electron density in disfavor of the five-membered chelate ring during the mixed ligand complex formation. The ligand exchange reaction between the nickel complexes can be followed by means of UV-Vis spectroscopy. All reactions obey formally a second order rate law. The crystal and molecular structure of Bu4N[Zn- (dmit)(Et2dtc)] is reported. The compound crystallizes orthorhombic, space group Pna21 with four molecules in the unit cell; a=22.573(4), b= 9.892(1), c=14.964(3) A. Distorted tetrahedral coordination geometry is found for the ZnS4 moiety with a dihedral angle of 89.6(2)° between the chelate planes. The ZnS distances in the dithiolene (dmit) part of the molecule are clearly shortened in comparison to (Bu4N)2 [Zn(dmit)2].

Molecular conductors based on selenium isologs of DMIT

The study of [(CH3)4N]x[ML2]-chelates (x = 0.5 − 2) with M = Ni, Pd, Pt and L = dmit (1,3-dithiole-2-thione-4,5-dithiolate), dmise (1,3-dithiole-2-selone-4,5-dithiolate), dsit (1,3-dithiole-2-thione-4,5-diselenolate), dsise (1,3-dithiole-2-selone-4,5-diselenolate) and dsis (1,3-diselenole-2-selone-4,5-diselenolate) shows distinct effects of the variation of the number of selenium and sulfur atoms on the redox and conducting properties. With increasing number of selenium atoms in the investigated compounds and subsequent decreasing number of sulfur atoms the oxidation potentials for the preparation of higher oxidized compounds (x < 1) decrease. The conductivity of these partially oxidized chelates decreases in the same order. In the crystal structure of [(CH3)4N]0.5[Ni(dsise)2] (space group Pccn, a = 7.423(3), b = 39.134(7), c = 11.829(4) A) the formation of [Ni((dsise)2] dimeric units is detectable, in which the nickel atom is square pyramidal coordinated by five selenium atoms. The room temperature conductivity of this chelate is high (12 S cm−1), but the temperature dependance of the conductivity is characteristic for semiconductors (0.06 eV). Therefore the difference when compared to the corresponding superconducting “all sulfur-compound” [(CH3)4N]0.5[Ni(dmit)2] is significant.

DARSTELLUNG VON PHOSPHONSäUREDIETHYLESTERN DURCH PHOSPHIT-KOPPLUNG VON 1,3-DITHIOL-2-THION-ANELLIERTEN KRONENVERBINDUNGEN

Abstract The reaction of the crowned 1,3-dithiole-2-thiones 1 and 2 with triethyl phosphite leads to the tetrathiafulvalenes 3 and 4, as well as 1,3-dithiole-2-yl phosphonate esters 5 and 6. The structure of the phosphonate 6 was confirmed by a single-crystal X-ray structure analysis. Using deuterated triethylphosphites (P(OCH2CD3)3 7, P(OCD2CH3)3, 8) the intramolecular proton transfer yielding the phosphonates was studied. Synthese der Phosphonsaureester wird gezeigt, das das zu deren Bildung notwendige Proton von einer CH2-Gruppe des P(OCH2CH3)3 geliefert wird.

Synthesis of novel tetrathiafulvalene derivatives with thiacrowns

Condensation of dicaesium 2-thioxo-1,3-dithiole-4,5-diselenolate(DSIT) with bis-alkylating polythioethers in high dilution leads to the thiacrown compounds 4–7. On treatment with triethyl phosphite, compounds 5–7 are converted into tetrathiafulvalene derivatives 8–10. The crystal structure of 6, and cyclic voltammograms of the tetrathiafulvalenes 9 and 10, are discussed.