C.T. Huys

A THERMODYNAMIC STUDY OF THE PROTONATION OF SOME SULPHIDE-CONTAINING PYRIDINES AND AMINO-PYRIDINES IN AQUEOUS SOLUTION

Abstract The protonation properties of pyridines with general formula (R = CH 3 , C 2 H 5 , CH 2 CH 2 OH; x = 1,2) and ( x, y = 1,2; 1,3; 2,2; 2,3) have been investigated by potentiometry and calorimetry at 25°C in 0.5 mole dm −3 K&{;NO 3 } solution. The protonation constants and the corresponding enthalpy and entropy changes are reported. The obtained values for the thermodynamic functions are discussed.

Sulphurnitrogen chelating agents. Part I. Some copper(II) complexes of sulphur-containing α,ω-diamines

Abstract Some series of five- and six-coordinated complexes of general formulate Cu{R2N(CH2)nS(CH2)mNH2}X2 or CU{R2N(CH2)nS(CH2)mNH2}ZY (n, m = 2 or 3; R = CH3 or H; X = NO−3, Cl−, Br−, ClO−4; Z = OAc−, NO−4, OH−) have been prepared and characterized. Structure assignment of the complexes is based on their conductivities in methanol, on their I.R. and electronic spectra. Dependent on the anion the n,m-R2NSN ligand may be facially or meridionally disposed around the central Cu(II) ion. The parallelism between the electronic spectra of the Solid {Cu(n,m-R2NSN)OAc}ClO4 complexes and the electronic spectra of the corresponding {Cu(n,m-R2NSN)3H2O}2+ species in aqueous solution suggests structural similarity.

Equilibrium studies of sulphide containing n-methyl substituted α,ω-diamines with protons, copper(II) and nickel(II) ions in aqueous solution

Abstract A series of sulphur-containing diamines of general formula R″R′N(CH 2 ) n S(CH 2 ) m NR′ 2 (R′ = H or CH 3 , R″ = CH 3 , n = 2 or 3 and m = 2, 3 or 4) has been prepared. Their protonation constants and the stability constants of their Cu(II) and Ni(II) complexes were determined at 25°C in 0.5 mol dm −3 K{NO 3 } medium, by the potentiometric method. The complex formation is discussed in comparison with analogous Cu(II) and Ni(II) complexes formed with non--substituted sulphur-containing diamines. In most cases normal ML 2+ and ML 2 2+ as well as protonated species were found.

A thermodynamic study of the protonation of some sulphur-containing α,ω-diamines in aqueous solution

Abstract The protonation equilibria in aqueous solution of α,ω-thiadiamines of general formula (R)(R′)N(CH 2 ) n ,S(CH 2 ) m NH 2 (R,R′= CH 3 or H) have been investigated potentiometrically and calorimetrically at 25° C in 0.5 mole dm −3 KNO 3 solution. The enthalpy and entropy changes are discussed in terms of intrinsic proton affinities and solvation effects.

Sulphur-nitrogen chelating agent—II. Mixed-metal binuclear (Cu2, Ag+) and mononuclear (Cu2+) solid state complexes of 1,4-diazo-7-thiaoctane and 1,5-diazo-8-thianonane. An infrared and reflectance spectral analysis

Abstract A series of CuLX 2 , CuL 2 X 2 , CuLYZ and AgCuL 2 Z 3 {X − = Cl − , Br − , NO − 3 ; Y − = OAc − ; Z − = NO − 3 or ClO − 4 ; L = 1,4-diaza-7-thiaoctane [2,2-NNS(Me)] or 1,5-diaza-8-thianonane [3,2-NNS(Me)]} have been prepared and characterized by means of elementary analysis, i.r. and electronic spectroscopy. All 1 : 1 complexes containing polyanions (NO − 3 , OAc − , ClO − 4 ) are five-coordinated species with the meridionally arranged thiadiamine acting as a tridentate. The remaining coordination positions are occupied by an asymmetric bidentate nitrate or acetate group. In contrast, in the 1 : 2 complexes, the thiadiamines are incompletely coordinated leaving one or even two sulphur donors free. These free sulphide-groups readily coordinate with the Ag(I) ions to form mixed-metal AgCuL 2 Z 3 -compounds.

A calorimetric and NMR determination of the microscopic protonation constants of some N-methyl-substituted α,ω-thiadiamines

Abstract A method has been developed to calculate the microscopic protonation constants for some asymmetric N -methyl-substituted α,ω-thiadiamines, n , m -(R)(R′)NSN (R = H or CH 3 : R′= CH 3 ; n = 2 or 3 and m = 2,3 or 4). The method is based on differences in enthalpies of protonation between the N -methyl substituted diamines n , m -(R)(R′)NSN and their corresponding non-substituted n , m -NSN analogues. A comparison of the calorimetric microscopic constants with those obtained with the 1 H-NMR technique confirms the value of the proposed calorimetric method. The microbasicity of the amino functions follows the sequence: secondary ⪢ primary ⪢ tertiary.

Thermochemical study of the stepwise protonation of 1,10-diaza-4,7-dithiadecane, and its complex formation with copper(II) and nickel(II) ions in aqueous solution

Abstract The behaviour of 1,10-diaza-4,7-dithiadecane (2,2,2-NSSN) in aqueous solution in equilibria with protons, Cu 2+ or Ni 2+ ions has been investigated potentiometrically and calorimetrically. The protonation constants for the ligand, and the stability constants for its complexes at 25°C in 0.5 mole dm −3 (K)NO 3 are reported, together with the corresponding thermodynamic parameters Δ G , Δ H and Δ S . The results are compared with those for 1-aza-4-thiapentane and 1,7-diaza-4-thiaheptane. The ligand 2,2,2-NSSN forms complexes of formula ML 2+ and MHL 3+ with both Cu 2+ and Ni 2+ . It is found that in the non-protonated 1:1 complexes the ligand acts as a tetradentate. In the CuHL 3+ complex, the ligand is bound through one nitrogen and two sulphur donors, whereas in the NiHL 3+ complex the ligand is probably bound through only one nitrogen and one sulphur donor. Explanations are suggested.

Thermochemical study of the complex formation of ag(I) with some sulphur-containing aminopyridines

Abstract The enthalpies of formation of the complexes between the silver(I) ion and some sulphur-containing aminopyridines of general formula N(CH2)n−1-S-(CH2)m-NH2 where n = 1, and m = 1,2; 1,3; 2,2; 2,3 have been determined by direct calorimetric titration at 25°C in 0.5 M (K)NO3 solution. The corresponding entropy terms, ΔS, have been calculated using the obtained enthalpy values and the previously reported ΔG values. In acid medium (pH ; 3) additional chelation through the pyridine nitrogen is obvious by a marked increase in the enthalpy of formation of the complexes AgL2H4+3, AgL2H3+2 and AgLH2+. The last complex dimerizes into a cyclic dimer Ag2L, H4+2. At still higher pH values (pH &>; 6) the participation of the amino group in the dimeric chelates Ag2L2H3+ and Ag2L2+2 is revealed again by a marked increase in the heat of complexation.

Evidence for equatorial and axial copper(II)-thioether interactions by means of electronic spectroscopy

Abstract The degree of Cu(II)-thioether interaction has been studied in some Cu(thiadiamine)·X 2 and Cu(thiadiamine)·YZ complexes (X − = NO − 3 , ClO − 4 ; Z − = OAc − ; Y − = ClO − 4 ). Evidence for strong equatorial Cu(II)-S bonding may be obtained from the energy of the σ(S) → Cu(II) ligand to metal charge-transfer transition (LMCT) as well as from an X-ray photoelectron spectroscopic determination of the binding energy shifts in the S 2 p levels. Weaker axial Cu(II)-S interaction can however only be detected by the study of LMCT spectra as the charge differences induced on the S atoms become too small to be revealed by ESCA.

Study of the bonding in Cu(II)-complexes with thiocarboxylates by means of i.r., XPS and u.v.-vis spectroscopy

Abstract Some 1: 1 complexes of Cu(II) and thiodiacetate, thiodipropionate and dithiodipropionate have been studied in the solid state by means of i.r., XPS and u.v.-vis spectroscopy. It was shown that there is a clear difference between the coordination of the thiodiacetate and (di)thiodipropionate ligands. The bonding of the former towards Cu(II) is achieved by a strong Cu(II)-sulphide bonding and two different kinds of Cu(II)-carboxylate interaction, one being monodentate, the other bidentate in character. The bonding of thiodipropionate and dithiodipropionate in their respective 1 : 1 Cu(II) complexes is quite similar and consists of weakly bound (di)sulphide and carboxylate groups.