Sture Fronæus

Dinuclear Complexes Contributing to Softness of Metal Acceptors

Since emf measurements with amalgam electrodes have been used, in most studies of the stabilities of complexes between soft metal acceptors and halide ions a series of investigations of the kinetics of electrode reactions were accomplished with halide systems of metal ions in the Groups 11 and 12 in aqueous and/or DMSO solutions. The aim was to establish which complexes contribute to the exchange current density, io. Such measurements are found to be a very sensitive method for identifying dinuclear complexes that can display much higher charge transfer rate constants than mononuclear complexes can. From these results it can be stated that hard acceptors do not show any tendency to form dinuclear halide complexes, whereas soft acceptors are apt to do so. This fact leads to the conclusion that dinuclear complexes have a strong internuclear bond. In determinations of the overall stability constant βj of a complex MLj there is an influence from a complex M2Lj with a constant βj′, resulting in the substitution of βj for (β j + 2aj βj′), where aj = [M] when the ligand number n = (CL – [L])/CM has the value j. An approximate value of the association constant, Kass, of the internuclear bond can be calculated from βj′ if βj is known. On the basis of these measurements the most probable types of the internuclear bonds are discussed.Since emf measurements with amalgam electrodes have been used, in most studies of the stabilities of complexes between soft metal acceptors and halide ions a series of investigations of the kinetics of electrode reactions were accomplished with halide systems of metal ions in the Groups 11 and 12 in aqueous and/or DMSO solutions. The aim was to establish which complexes contribute to the exchange current density, io. Such measurements are found to be a very sensitive method for identifying dinuclear complexes that can display much higher charge transfer rate constants than mononuclear complexes can. From these results it can be stated that hard acceptors do not show any tendency to form dinuclear halide complexes, whereas soft acceptors are apt to do so. This fact leads to the conclusion that dinuclear complexes have a strong internuclear bond. In determinations of the overall stability constant β j of a complex ML j there is an influence from a complex M2L j with a constant β j ′, resulting in the substitution of β j for (β j + 2a j β j ′), where a j = [M] when the ligand number n = (CL – [L])/CM has the value j. An approximate value of the association constant, Kass, of the internuclear bond can be calculated from β j ′ if β j is known. On the basis of these measurements the most probable types of the internuclear bonds are discussed.

An Investigation on some Sulphato Complexes in Aqueous Solution with Infrared Spectroscopy

Infrared spectra in the range 1400 – 850 K have been recorded for several metal sulphates in aqueous solution. For this purpose 8,8 µ thick cells with “IRTRAN — 2” windows have been used. In the frequency region mentioned the free sulphate ion absorbs radiation at 1104 K corresponding to the asymmetric S-O vibration (ν 3). From solid state investigations (1) it is known that in the spectrum of sulphato complexes this absorption peak is split into two or three new peaks depending upon whether the symmetry of the sulphate ion is decreased to C3v or C2v. This corresponds to a mononuclear, unidentate complex and a polynuclear or possibly a mononuclear bidentate complex, respectively. Furthermore, the symmetric S -O vibration (ν 1), which is infrared inactive for the free ion, becomes apparent in the spectra of sulphato complexes.