Z. Eeckhaut

A potentiometric study of the silver(I) complexes of some sulfur-containing amines

Abstract A series of sulfur-containing amines of general formula R′—S—(CH 2 ) n NR 2 where R′ = CH 3 , C 2 H 5 , n C 3 H 7 , (CH 3 ) 3 C, HOCH 2 CH 2 , R = H, CH 3 , C 2 H 5 , CH(CH 3 ) 2 and n = 2, 3 has been prepared and the protonation constants were measured at 25°C and μ = 0.50 M (KNO 3 ). The stability constants of the silver complexes formed in acid, neutral and alkaline medium have been determined at 25°C and μ = 0.50 M (KNO 3 ) by simultaneous pH and pM measurements. The complex formation is discussed in comparison with the silver complexes formed with diamines and thioether ligands and in terms of the Taft σ-functions for the substituents.

Benzyl compounds—VII: The far infrared and Raman spectra of meta-substituted benzyl compounds

Abstract The infrared and Raman spectra of some meta-substituted benzyl derivatives have been examined in the low-frequency region below 650 cm−1. Evidence has been found for a totally asymmetric stereochemical structure. The presence of a torsional frequency is a proof for the existence of a rotational barrier about the C(phenyl)-C(methylene) bond.

Polymeric complexes between nickel(II) and 2-mercaptoethanol and 3-mercapto-1,2-propanediol

Abstract The complexes between nickel(II) and 2-mercaptoethanol(MEL) and 3-mercapto-1,2-propanediol(MPD) were studied in aqueous solution by a pH-metrical method, at 25°C and in 0.5 M KNO 3 . According to Sillens theory the complex formation can be represented by a “core + links” system B (A 2 B) n , where B means the metal ion and A the ligand. At any rate n tends to very high values. It is possible that with an excess of the ligand complexes with formula (BA 2 ) n are formed. Theoretically n can take values form zero to infinite. In practice no difference can be found between an infinite value of n and very high values. So the mechanism can be represented by a chain polymeric structure. The reduced stability constants of the system were found by comparing experimental data with theoretical curves.

Polynuclear complex formation between zinc(II) and 2-mercaptoethanol and 3-mercapto-1,2-propanediol

Abstract Polynuclear complex formation between zinc(II) and 2-mercaptoethanol (MEL) and 3-mercapto-1,2-propanediol (MPD) was studied by a pH-metrical method at 25°C and in 0.5 M KNO 3 . According to Sillens theory the complex formation can be represented by a «core+links» system B (A 3 B) n where B means the metal ion and A the ligand. The maximum value of n was found to be five. So only the following complexes are present: B 2 A 3 , B 3 A 6 , B 4 A 9 , B 5 A 12 , B 6 A 15 . The stability constant of each of these complexes was determined using the extrapolation method of Fronaeus and Leden. The stability constants were tested and refined by comparing theoretical curves with the experimental data.

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.

NMR study of donor-acceptor complexes—I. Proton magnetic resonance of substituted aryl-phosphorus compounds and their boronhalide complexes

Abstract The differences in chemical shift of the ring protons in the ( X C 6 H 4 ) 3- n PCl n compounds and in their B X 3 complexes should be explained by the substituent effects S F and S Cl , first described by P. Diehl. The substituent effects of the phosphorus containing groups ( S P ) were calculated for the unsubstituted arylphosphines and their complexes. These values indicated that a correlation exists between the shielding of the ortho protons and the stability of the D-A complexes. The decrease of the shielding of the ortho protons (ΔδH 0 ) and the increase of the coupling constant (Δ J P-J 0 ) on complexation appeared to be both dependent on the stability of the complexes.

The problem of σ- and π-bonding in the tin substituted tetracarbonyl cobalt compounds RlXmSn {Co(CO)4n}, R = alkyl, phenyl, X = halogen, l + m + n = 4

Abstract The results of each type of spectroscopic research on organometallics, such as r i x m Sn- [Co(CO) 4 ] n (R = Alkyl, Phenyl, X = Halogen, l + m + n = 4) provide information clarifying the bonding in these heteronuclear metal—metal bonded molecules. This report is a concise survey comparing the conclusions drawn from nuclear magnetic, nuclear quadrupole and nuclear -γ resonance spectroscopy, together with the polar characteristics investigated by the dipole moments method and the vibrational data obtained from the far infrared region. The experimental data are critically discussed in terms of (1) metal-metal σ bonding changes, (2) d π -d π contributions which may occur between a group IV-B metal and a transition metal and (3) p π -d π overlap resulting from a back-donation of the unshared halogen p -electrons into symmetry-proper vacant d -orbitals of the tin atom.

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.