C. Preti

Thiazolidine-2-thione complexes with group VI B metal-carbonyls

Abstract By u.v. irradiation of toluene solutions of [M(CO)6] and ttz the complexes [M(CO)5ttz] (where: MCr, Mo, W, and ttzthiazolidine-2-thione) were obtained, which are yellow, crystalline, diamagnetic and non-electrolytes. By means of the mass-spectra, i.r. and n.m.r. studies a full characterization of the free ligand and of that the co-ordination bond takes place through the sulphur atom of thioketonic group. A SN1-type mechanism of the photochemical reactions was pointed out by determining the quantum yields.

Group IIB metal and VIB metal-carbonyl thiomorpholin-3-thione derivatives

Abstract Using thiomorpholin-3-thione (ts) as ligand the complexes M(CO)5ts (where M = Cr, Mo, W), which are yellow, crystalline, non-electrolyte and diamagnetic, were obtained. Complexes of the types MX2ts2 and MX2ts (M = Zn, Cd, Hg; X = Cl, Br, I) were obtained as diamagnetic and non-electrolyte compounds. On the basis of i.r. and PMR spectra we suggest that the Cr, Mo and W-pentacarbonyl-derivatives have C4ν symmetry and are S-bonded through the thioketonic group, while all the IIB group derivatives seem to be N-bonded.

Group IIB metal complexes with thiazolidine-2-selenone and thiazolidine-2-one as ligands

Abstract 1:1 or 1:2 complexes of thiazolidine-2-selenone and thiazolidine-2-one with zinc(II), cadmium-(II) and mercury(II) halides have been prepared and characterized by molecular conductance and i.r. spectral measurements. It is suggested that 1:1 complexes are dimeric tetrahedral structures with halogen bridges; 1:2 derivatives have a monomeric tetrahedral stereochemistry. Assignments for the metal-ligand and metal-halogen modes have also been made.

Cobalt(II) and nickel(II) complexes with Para and Meta substituted benzeneseleninic acids

Abstract The benzeneseleninate anion forms complexes with cobalt(II) and nickel(II) of the type - [ M ( X -PhSeO 2 ) 2 (H 2 O) 2 ]. I.R. spectra of these compounds suggest that the complexes are seleninato O , O ′ with the ligand bidentate. The electronic absorption spectra were studied and values of the spectral parameters were determined. All the complexes have a distorted octahedral D 4 h symmetry.

Silver and gold(I) complexes with thiomorpholin-3-one: kinetics of reduction of gold(III)

Abstract White, crystalline, diamagnetic complexes [AuXT] (where X = Cl, Br, and T = SCH 2 CH 2 NHCOC H2) where obtained by reduction of [AuX4]− with T. The kinetic study has been carried out by absorbance and pH measurements in 0.5 M KX in 50/50 (vol.) EtOH/H2O. The mechanism is dominated by a preliminary hydrolysis equilibrium. After the addition of T the ligand replaces the hydroxyl ion and, after another hydrolysis step, reduces the metal to gold(I). The k and ΔE* values are reported. A white, crystalline, diamagnetic complex [AgT]NO3 was obtained from the reaction between AgNO3 and T. All complexes are S-bonded to the metal.

Palladium complexes with 3-thiomorpholinone: Preparations and reactions

Abstract Some reactions between palladium compounds and 3-thiomorpholinone (T) were examined, the compounds PdCl 2 T 2 and PdBr 2 T 2 being isolated in solid state. The reaction between PdBr 4 2− and T is quantitative and may be followed by means of conductometric or high-frequency titrations; the compound PdCl 2 T 2 is fairly soluble in water and hydrolises to form the compound Pd(OH) 2 T 2 . Spectrophotometric study of the system formed from PdCl 4 2− and T reveals that the compound PdCl 2 T 2 is formed instantaneously and then reacts with the excess of PdCl 4 2− to form PdCl 3 T − . The reaction follows a second order mechanism. The instability constants of the two compounds and the rate constant are calculated at 25°C. The 3-thiomorpholinone compounds of Palladium and Platinum are examined by means of I.R. spectrophotometry and the resultant spectra are discussed. The results of the enquiry suggest that this category of compounds is most likely to have a square trans- planar configuration in which the ligand is bonded to the metal via sulphur.

The kinetics of reduction of palladium(IV) by 3-thiomorpholinone

Abstract Kinetic investigation on redox reaction of the complex [PdCl 6 ] 2− with 3-thiomorpholinone by pH measurements is reported. The [PdCl 6 ] 2− complex undergoes reduction with formation, in aqueous solution, of the final compound trans-[Pd(OH) 2 T 2 ] (T = 3-thiomorpholinone). The kinetic process is more complicated than the similar reduction of platinum(IV) to platinum(II) by the same ligand and proceeds by some different steps. The first step is the hydrolysis equilibrium of [PdCl 6 ] 2− with [PdCl 5 OH] 2− followed, in our interpretation, by a substitution of T to the hydroxyl ion with formation of the complex [PdCl 5 T] − and then, by some hydrolysis and substitution steps, of the complex [PdCl 3 T 2 OH]. The latter reacts with the ligand with reduction to trans-[PdCl 2 T 2 ] and, by two additional hydrolytic stages, to trans-[Pd(OH) 2 T 2 ]. pH measurements carried out in KCl 3 M, in NaClO 4 0.1 M, at 20, 25, 30, 35, and 40°C, lead one to propose this interpretation; the values of the rate constants are reported for hydrolysis equilibrium, the first substitution of T and the reduction stage, which steps are supposed to be slow; the corresponding activation parameters are also reported. The rate constants for the reduction step are independent of the ionic strength. The results are correlated to the coordinating properties of the ligand T.

Thiomorpholin-3-one transition metal complexes

Abstract The preparation of iron(III), iron(II), nickel(II), copper(I) and copper(II) complexes with thiomorpholin-3-one is described. Electronic spectra, infrared spectra and magnetic moments are reported and discussed in terms of suggested structures of the complexes.

Nickel(II) and cobalt(II) complexes with thiazolidine-2-thione

Complexes of thiazolidine-2-thione (ttz) were prepared and studied by magnetic techniques and u.v. visible, and i.r. spectroscopy. Pseudotetrahedral complexes [M(ttz)2X2] are formed with CoX2(X = Cl, Br, or I) and Nil2, while octahedral or distorted octahedral complexes [M(ttz)2X2] are formed with NiX2(X = Cl or Br). The ‘inner’ complex [Ni(C3H4NS2)2] has a distorted square-planar structure. It appears that this ligand co-ordinates through the sulphur heteroatom in tetrahedral complexes and through both sulphur atoms in octahedral ones.

An infrared study on benzeneseleninic acids and salts: assignments and substituent effects

The i.r. spectra of several meta- and para-substituted benzeneseleninic acids and salts as solids and in solution have been recorded. The structures of the CSeO2– and CSeOOH groups have been assessed from the solid-phase spectra. These assignments have also been tested by use of empirical relationships between force constants on one hand and vibration frequencies or bond orders on the other, and by comparison of the spectra of the benzeneseleninic derivatives with those of diphenyl selenoxide and of diphenyl diselenide. The solution spectra have been used to correlate frequency shifts and Hammetts σ-values. The substituent effect on benzeneseleninic derivatives is intermediate between the corresponding effects on benzoic and on benzenesulphinic acids.