P. Cassoux

Synthesis, characterization and properties of highly conducting organometallic polymers derived from the ethylene tetrathiolate anion

Abstract The preparation and electrical conductivity studies of a series of organometallic polymers, (MC2S4x−)n (M = Ni, Pd, Pt, Au), derived from the ethylene tetrathiolate anion are described. The synthesis of the precursor molecules or molecular complexes (PhCH2)4(C2S4), (AsPh4)2[M(C3OS4)2], (C3)OS4Pd(dppe) and (AsPh4)2[(C3OS4)Cu(C2S4)Cu(C3OS4)] is also described. From these results the different possible formation mechanisms of the polymers are discussed. The polymers show high compaction powder conductivity at room temperature (from 10−5 to 5Ω−1 cm−1). [Na0.31(NiC2S4)]ν, one of the most conductive polymers, exhibits a metal-like temperature dependence of conductivity, as evidenced by voltage shorted compaction (VSC) experiments. These conductivity properties are to be related with the degree of partial oxidation (DPO) observed in the polymers studied.

Automatic ir drop correction for studies of electrochemical systems

Abstract The interest of automatic ir drop correction by the interrupt method is evaluated by carrying out electrochemical studies on ferrocene in various non-aqueous solvents, using a home-made microcomputer-controlled potentiostat. Special attention is devoted to voltammetry and cyclic voltammetry.

Electrochemical, EPR, and crystal structure studies on mixed-ligand 4,5-dimercapto-l,3-dithia-2-thione phosphine complexes of nickel, palladium and platinum, M(dmit)(dppe) and Pt(dmit)(PPh3)2

Complexes of the type M(dmit)(Phos)2 (M = Ni, Pd, Pt; Hsdmit = 4,5-dimercapto-1,3-dithia-2-thione; (Phos)s = dppe = 1,2-bis-diphenylphosphinoethane. M = Pt; (Phos)s = (PPha),) have been studied by means of X-ray diffraction method, and electrochemical techniques coupled with EPR spectroscopy. The crystal structure of Pt(dmit)(dppe) has been determined: this compound crystallizes in the monoclinic space group P2r/n witha = 18.267(3), b = 16.903(3), c = 9.748(2) A, fl= 95.50(2)” and 2 = 4. The environment of the platinum atom is nearly square-planar (Pt-P = 2.254(3), I’-S = 2.3 1 l(3) A) with very slight tetrahedral distortion. The cyclic voltammetry parameters for the oxidation and the reduction of the studied complexes have been determined in CHzClz: Ni(dmit)(dppe) undergoes a quasi-reversible one-electron reduction step. Pd(dmit)(dppe) undergoes an irreversible two-electron reduction step. Both Pt(dmit)(dppe) and Pt(dmit)(PPhs)s do not undergo reduction. All three M(dmit)(dppe) (M = Ni, Pd, Pt) undergo a reversible one-electron oxidation step, the Pt(dmit)(PPh& a quasi-reversible one. EPR studies of the electrogenerated complexes show that the reduction of Ni(dmit)(dppe) is metal-based and that the [Ni(dmit)(dppe)]- is a nickel(I) species. The oxidation of the M(dmit)(dppe) complexes is ligand-based and the unpaired electron in the [M(dmit)dppe]+ species is mainly delocalized on the dmit ligand. plexes may be used as molecular model systems of metal-tetrathiolato polymers (MC2S4), [4,5]. These polymers have aroused great interest because of their high compaction powder conductivity (up to 50 s2-’ cm-’ [6,7]). They have been the subject of several research works including their transport properties and degree of partial oxidation [5,8], magnetic behavior [5,9] and formation mechanism [4-71. The formation mechanism of these polymers that we have proposed [5] was based upon the unexpected obtaining of mononuclear metal complexes, M(dmdto)(Phos)2 and M(dmit)(Phos)? ((Phos)2 = dppe = 1,2-bis-diphenylphosphinoethane; (Phos)s = (PPhs)2; H2dmdto = 4,5-dimercapto-1,3-dithia-2one). These complexes were characterized by elemental analysis, IR spectra and mass spectra [4], but none of the crystal structures had been determined. We report here the crystal structure of one member of these series, Pt(dmit)(dppe).

Synthesis and resonance Raman study of conductive iodinated materials derived from M(dmit)(bipy) complexes

Abstract The synthesis and characterization of the M(dmit)(bipy) complexes (M = Ni(II), Pd(II), Pt(II); H2dmit = 4,5-dimercapto-1,3-dithiole-2-thione; bipy = 2,2′-bipyridine) and of the iodinated [M(dmit)(bipy)]I compounds (M = Pd or Pt) are described. The conductivity of M(dmit)(bipy) increases upon iodination by a factor of 106, and is ≈ 4 × 10 −3 Ω −1 cm −1 for the [M(dmit)(bipy)]I compounds. The nature of the iodine species in these solids is determined by ultraviolet-visible and resonance Raman spectroscopy. The only polyiodide present is I3− and, thus, the charge distribution can be expressed as [M(dmit)(bipy)+0.33][I3−]0.33.

[Cp2V(μ‐η2:η4‐butadiyne)MCp2′] (M=Ti, Zr; Cp′=C5H5, C5H4SiMe3): Heterodimetallic Complexes from a Bis(alkynyl)metallocene and Vanadocene—Unexpected Structure of [Cp2V(μ‐η2:η4‐butadiyne)Zr(C5H4SiMe3)2] Containing Two Planar‐Tetracoordinate Carbon Atoms

Titanium–vanadium and zirconium–vanadiumcomplexes are obtained from the reaction between bis(phenylethynyl)titanocene, or -zirconocene, and vanadocene. The X-ray structure analysis of [Cp2V(μ-η2-η4-butadiyne)Zr(C5H4SiMe3)2] (depicted on the right) reveals that the [Cp2V] metallocene moiety is bonded to a butadiene (or butadiyne) framework through the two internal carbon atoms and that the [(C5H4SiMe3)2Zr] moiety is bonded to this unit through the two internal carbon atoms and the two external carbon atoms. Both internal carbon atoms of the butadiene skeleton are planar-tetracoordinate.

Crystal structures and electrochemical properties of two phases of tetrabutylammonium bis(1,3-dithiole-2-thione-4,5-diselenolato)nickelate(III)

Abstract The crystal structures of two phases (α and β) of [Bu4N]2[Ni(dsit)2]2 are reported (dsit=1,3-dithiole-2-thione- 4,5-selenolate). The compound crystallises either in blocks (α-phase) or needles (β-phase). The α-phase crystallises in the triclinic space group P 1 , with a=12.381(3), b=14.009(2), c=9.571(1) A, α=94.43(1), β=99.61(2), γ=81.32(2)° and Z=1 with the asymmetric unit having the formula Ni2C44H72N2S12Se8. The β-phase crystallises in the triclinic space group P 1 , with a=11.820(1), b=14.998(1), c=9.517(1) A, α=96.980(8), β=100.251(9), γ=76.926(8)° and Z=1 with the asymmetric unit having the formula Ni2C44H72N2S12Se8. The structures were solved by direct methods, and refined by Fourier and least-squares techniques. Both crystal structures differ only marginally. They consist of anionic dimers made up of two chemically bound Ni(dsit)2 units. The Ni atom is square pyramidally coordinated by five selenium donor atoms, with the apically bridging Niue5f8Se distances (2.48 and 2.47 A for α- [Bu4N]2[Ni(dsit)2]2 and β-[Bu4N]2[Ni(dsit)2]2, respectively) being significantly longer than the equatorial distances (2.316–2.347 A). In the β-phase one of the thionyl groups and three of the four butyl chains of the cations are in disorder. Because of the bulky nature of the cations, no short interdimer contacts are present in the lattices. Cyclic voltammety studies of [Bu4N]2[Ni(dsit)2]2 in acetone show a first reversible 2[Ni(dsit)2]−⇌[Ni(dsit)2]22− couple at E1/2=−0.12 V (versus Ag/AgCl), and a second quasi-reversible couple involving a single anodic peak at 0.18 V and two reduction peaks at 0.08 and −0.01 V.

A new π donor-acceptor compound derived from tetraphenyldithiapyranylidene and bis-(1,3-dithia-2- thione-4,5-dithiolato)-nickelate: crystal structure and epr study

Abstract The electrosynthesis, X-ray crystal structure and EPR study of the 1:1 adduct between tetraphenyldithiapyranylidene and bis-(1,3-dithia-2-thione-4,5-dithiolato)-nickelate, (DIPSΦ4)[Ni(dmit)2], are reported. The triclinic unit cell contains one Ni(dmit)2 and one DIPSΦ4 entity, the molecular centre of each lying on a crystallographic centre of symmetry. The structure is characterized by a loose stacking (10 A) of Ni(dmit)2 units along [001], with no strong intermolecular interaction, consistent with the low electrical conductivity. Single-crystal EPR spectra show a single, broad line for any orientation. The angular dependences of the line width and of the g-factors have been determined, as well as the principal g-values and directions. The temperature-dependences of the susceptibility, the line width and the g-factor have been measured in the range 4–300 K. Analysis of these results indicates that dipolar spin-spin interaction takes place in this highly electron- correlated semiconducting system with complete charge transfer between the donor DIPSΦ4 and the acceptor Ni(dmit)2.

Electrochemical Studies of the Formation Mechanism of (cation) x [Ni(dmit)2 Conductive Compounds and of their Non-Integer Oxidation State

Abstract The mechanism of electrocrystallization of (cation) x [Ni(dmit)2 (cation = NHMe+ 3, NMe+ 4) conductive compounds is studied under non-stationary conditions by cyclic voltammetry using ultramicroelectrodes at high potential-scan rates. It is shown that the formation of non-integer oxidation state compounds proceeds through one-electron transfers combined with chemical reaction between [Ni(dmit)2 − and [Ni(dmit)2 0 electrogenerated species exhibiting integer charges. The non-integer oxidation state in (cation) x [Ni(dmit)2 compounds (cation = NBu+ 4, AsPh+ 4, NH2Me+ 2, NH3Me+), measured by the non-integer value of x, is determined under stationary conditions by use of the carbon paste electrode at very low potential-scan rates.

Thermoanalytic studies of the pyrolysis of CpTiCl2N(SiMe3)2 and its use as a precursor for the chemical vapor deposition of titanium carbonitride

Abstract The synthesis and characterization of a triclinic allotropic form of CpTiCl2N(SiMe3)2 is reported. Thermal analysis and simultaneous mass spectroscopy studies carried out under nitrogen and hydrogen show that this complex decomposes to titanium carbonitride at about 350–370°C. The weight loss observed under hydrogen flow is higher than that observed under nitrogen flow. Elemental analyses show that the residue from nitrogen pyrolysis is more carbon rich than the residue from hydrogen pyrolysis, indicating that carbon is more readily removed during pyrolysis in hydrogen. Chemical vapor deposition (CVD) experiments using CpTiCl2N(SiMe3)2 as an organometallic precursor have been carried out on glass, silicon and steel, using a hot wall type CVD reactor. Shiny, bronze—black, metallic thin films have been obtained and characterized as titanium carbonitride by EDS and XPS analyses.

Tentative partial oxidation of the nickel(II) potassium-dithiooxalato complex: Existence of iodine an adduct K2Ni(S2C2O2)2I in solution and crystal structure of a new polymorphic form of K2Ni(S2C2O2)2 (‘black’ form)

Tentative partial oxidation of ‘red’ nickel(II) potassium-dithiooxalate K 2 Ni(S 2 C 2 O 2 ) 2 by iodine results in a K 2 Ni(S 2 C 2 O 2 ) 2 I adduct. This adduct was identified in solution but could not be isolated in the solid state. Operating with K 2 Cr 2 O 7 surprisingly leads to a polymorphic ‘black’ form of K 2 Ni(S 2 C 2 O 2 ) 2 which is also obtained as by-product of the rapid decomposition of the iodine adduct. The X-ray structure of the new ‘black’ form has been solved (P2 1 /n; Z = 2; a = 11.0369(10) A , b = 4.1911(3) A , c = 12.7221(17) A , β = 111.784(9)°). Full-matrix least-squares refinement of 70 variables gave a final value of the conventional R index (on F) of 0.022 for 1420 reflections having F 2 o > 3σ (F 2 o ). Planar Ni(S 2 C 2 O 2 ) 2 units stack along the b direction (Niue5f8 Ni = 4.19 A ) which is not the case in the ‘red’ form. Crystallographic relationship between both ‘red’ and ‘black’ species is discussed.