Stereochemical trends of metal derivatives of some heterocyclic-2-thiones and thiosemicarbazones

The interaction of heterocyclic thiones/thiosemicarbazones with metals has been the subject of several investigations as these ligands contain chemically active groups,-N(H)-C(=S)-↔ -N=C(-SH)-,and are useful model compounds for sulphur-containing analogues of purine and pyrimidine bases. Heterocylic-2-thiones bind to metals in several ways and lead to the formation of monomeric or polymeric complexes. For example, the simplest prototype of heterocylic-2-thiones, namely, pyridine-2-thione has several ways of binding, notably, terminal S-bonding and S-bridging (in neutral form), while in anionic form the modes are terminal S-bonding, S-bridging, N,S-chelation, N,S-bridging, N,S-chelation-cum-S-bridging and N,S-bridging-cum-S-bridging. Similarly, thiosemicarbazones bind to metals as S-bonded unidentates or N,S-chelates. In this paper, the chemistry of pyridine-2-thione, its N-oxide, 2-(benzylthio)pyridine-1-oxide thione with metals like iron(II), ruthenium(II), nickel(II), palladium(II), platinum(II), copper(I), copper(II), silver(I) and mercury(II) is briefly described. As regards thiosemicarbazones, focus is only on two compounds, namely organomercury(II) and organothallium(III). A variety of new molecules, well characterised by NMR and X-ray crystallography, is introduced.     

Sorption of inorganic nanoparticles in woven cellulose fabrics

Titanium dioxide was deposited from aqueous suspension onto cellulosic surfaces.Titania was sourced from Degussa (P25TM,70:30 anatase:rutile).Dry uptake of particles was shown to be rapid and dominant with one-third of the deposition occurring in less than 30 s and over one-half in the first minute.Isotherms were recorded to compare the rate of titanium deposition on dry and pre-wetted cotton.In the dry case uptake reached a maximum in 30 min whereas in the pre-wetted case the uptake was seen to continue beyond 180 min.A broad trend of higher deposition occurring at lower pH was seen,corresponding to the region where surface charges were opposite and thus attractive.Dry pickup was less significant at high pH.The response to varying ionic strength was complex and was attributed to the combined effect of charge screening,particle aggregation and consequent particle entrapment or occlusion.Titania deposition into the interstices of woven cotton sheets resulted in the formation of inorganic,nanoparticulate skeletons which could be isolated by controlled combustion of the cellulose and thus cotton was suggested to have potential for the templated synthesis of high surface area semiconductor materials.     

Construction of a novel copper(I) chain polymer of hexanuclear Cu6(2-SC5H4NH)6I6 cores with a new (mu 3-S) mode of bonding of pyridine-2-thione and of an unusual triangular Cu3I3(dppe)3(2-SC5H4NH) cluster

The reactions of copper(I) iodide with pyridine-2-thione (2-SC(5)H(4)NH) in the presence of a series of diphosphane ligands, Ph(2)P[bond]X[bond]Ph(2)P [X = [bond](CH(2))(m)[bond], m = 1(dppm), 2 (dppe), 3 (dppp), 4 (dppb); [bond]CH[double bond]CH[bond] (dppen)], yielded an iodo-bridged hexanuclear Cu(I) linear polymer, [Cu(6)(mu(3)-SC(5)H(4)NH)(4)(mu(2)-SC(5)H(4)NH)(2)(I(4))(mu-I)(2)-](n).2nCH(3)CN (1). A similar reaction with 1,2-bis(diphenylphosphino)ethane (dppe) and 2-SC(5)H(4)NH yielded a triangular cluster, Cu(3)I(3)(dppe)(3)(2-SC(5)H(4)NH), 2. In the chain polymer 1, three Cu(I) iodide and three 2-SC(5)H(4)NH ligands combined via bridging S donor atoms to form a boat-shaped trinuclear Cu(3)S(3)I(3) core, and two such cores combined in an inverse manner via four S-donor atoms (mu(3)-S) to form a centrosymmetric hexanuclear repeat unit, Cu(6)S(6)I(4)(mu-I)(2-), which finally formed the iodo-bridged infinite linear chain polymer 1. Linear chains are separated by the nonbonded acetonitrile molecules. Polymer 1 is the first such example of a linear chain formed by the hexanuclear Cu(6)S(6)I(6) core in copper chemistry as well as in metal-heterocyclic thioamide chemistry. In addition, it has the first mu(3)-S mode of neutral pyridine-2-thione ever reported. In the moiety Cu(3)I(3)(dppe)(3) of 2, two copper(I) centers are bridged by the iodide ligands forming a Cu(mu-I)(2)Cu core, while a third copper(I) center is terminally bonded to another iodide ligand. Polymer 2 is also rare, and the first triangular cluster of Cu(I) with an heterocyclic thioamide.     

A solid state e.s.r. study of manganese(II) halide-triphenylphosphine oxide complexes

Summary Ph₃PO adducts with manganese(II) halides, viz. MnX₂-(OPPh₃) ₂ (X = Cl or Br) were heated for 1 h and their X-band e.s.r. spectra recorded at room temperature. The chloride adduct, MnCl₂(OPPh₃)₂ completely transformed into the symmetrised product, [Mn(OPPh₃)₄] [MnCl₄] at 175 and 225° C. The bromide adduct, MnBr₂-(OPPh₃)₂, which is probably a mixture of its nonionic and ionic forms at room temperature, showed hyperfine coupling in the g = 2.029 region.     

A cyclic voltammetric study of iron(II)/ruthenium(II) complexes with bis(tertiary phosphines)

Summary Nine complexes of Fe^IIRu^II with bis(tertiary phosphines), namely, 1,2-bis(diphenylphosphino)ethane (dppe), 1,2-bis (diphenylphosphino)ethylene (dppen) and o-phenylenebis (diphenylphosphine) (o-diphos) were studied using cyclic voltammetry. The half-wave potentials for the complexes studied are: (1) [FeCl₂(dppe)], 0.050V; (2) [Fe(NCS)₂(dppe)₂], 0.265V; (3) [RuCl₂(dppe)₂], 0.548V; (4) [FeCl₂(dppen)₂], 0.225V; (5) [Fe(NCS)₂-(dppen)₂], 0.290V; (6) [RuCl₂(dppen)₂], 0.690V; (7) [FeCl₂(o-diphos)₂] 0.160V; (8) [Fe(NCS)₂(o-diphos)₂] 0.582V; and (9) [RuCl₂(o-diphos)₂], 0.265V. The redox potentials are related to the nature of the ligand, the nature of the metal, the stereochemistry of the complex and the ligand field strength.     

A mercury(II) ion-selective electrode based on neutral salicylaldehyde thiosemicarbazone

A new ion-selective PVC membrane electrode based on salicylaldehyde thiosemicarbazone as an ionophore is developed successfully as sensor for mercury(II) ions. The electrode shows excellent potentiometric response characteristics and displays a linear log[Hg²⁺] versus EMF response over a wide concentration range of 1.778×10⁻⁶-1.0×10⁻¹ M with Nernstian slope of 29 mV per decade with the detection limit of 1.0×10⁻⁶ M. The response time of the electrode is less than 30 s and the membrane electrode operates well in the pH range of 1.0-3.0. The lifetime of the sensor is about 2 months. The electrode shows better selectivity towards Hg²⁺ ions in comparison with the alkali, alkaline and some heavy metal ions; most of these metal ions do not show significant interference (K^Pot_Hg,M values of the order of 10⁻³-10⁻⁴). The present sensor showed comparable or even better performance vis-à-vis similar PVC based ion-selective electrodes reported in literature. The sensor was also applied as an indicator electrode for potentiometric titration of Hg²⁺ions with I⁻ and Cr₂O₇²⁻.     

X-ray crystal and molecular structure of dichlorobis [2(1H)-pyridinethione-S]iron(II)

Attempts to prepare the mixed ligand complex, FeCl₂(pyS)(Ph₃P)₂ from the reaction of iron(III) chloride with 2(1H)-pyridinethione-S(HpyS) and triphenylphosphine(Ph₃P) in ethanol instead formed FeCl₂(HPyS)₂ characterized by X-ray crystallography. The structure was determined by the heavy atom method, using MoK diffractometer data, and refined by full-matrix least squares toR=0.049 for 1123 observed reflections. The molecule possesses twofold symmetry with a distorted tetrahedral geometry about the iron(II) center with S-Fe-S and Cl-Fe-Cl bond angles of 98.76(5)° and 115.79(5)° and Fe-S and Fe-Cl bond distances 2.345(1) Å and 2.288(1) Å, respectively. Hydrogen bonding between NH and chlorine atoms leads to a polymeric type structure of linked molecules running approximately parallel to thea axis.     

Crystal structure of [bis 1,2-(diphenylphosphino)ethane]-bis(pyridine-2-thiolato)ruthenium(II)

The Ru atom in the title compound, [Ru(dppe)(2-pyS)₂] exists in a distorted octahedral geometry defined by a dppe ligand and two 2-pyS anions which function as bidentate ligands via their N- and S-atoms. Important interatomic parameters are Ru-P2.240(3), 2.256(3); Ru-N 2.131(8), 2.136(8); Ru-S 2.413(3), 2.428(3) Å; P-Ru-P 84.1(1), S-Ru-S 155.0(1) and N-Ru-N 87.5(3)°. Crystals are monoclinic, space groupP2₁/c, with unit cell dimensionsa=10.342(1),b=31.145(6),c=11.107(2) Å,=113.80(1)° andZ=4. The structure was refined to finalR=0.064 for 3057 reflections withI2.5(I).     

Inclusive and exclusive measurements in the projectile breakup of 7Li

The inclusive and exclusive measurements were carried out for ⁷Li projectile breakup on ²⁷Al target at 48 MeV. In the inclusive data we have observed a broad peak around the beam velocity for alphas and tritons. The exclusive data for alpha-triton coincidences show good agreement with the post-form DWBA theory of breakup reactions.