ESR and electronic spectral parameters of four tetraphenylborate salts of Cu(II) complexes are presented and compared to the analogous tetrafluoroborate and perchlorate salts.
ESR and electronic spectral parameters of four tetraphenylborate salts of Cu(II) complexes are presented and compared to the analogous tetrafluoroborate and perchlorate salts.
D.c. polarographic and cyclic voltammetric studies have been carried out on aqueous solutions (10−4−10−3 M) of 249Cf, Sm and Gd. From the present data and the established electrochemical behavior of Sm and Gd, it can be inferred that Cf(III) is reduced in two steps at the mercury-drop electrode, first to Cf(II), followed by the Cf(II) being reduced to Cf(Hg). The potentials for the two electrochemical steps are −1.47 and −1.68V vs NHE, respectively.
The kinetics of the Fe(II) reduction of trans-chloro, bromo and iodopyridinebis(dimethylglyoximato)Co(III) have been studied at 30.0±0.1°C and I = 1.0 mol. dm−3(NaClO4) in the [H+] range 0.0043–0.115 mol. dm−3. The reaction showed an inverse dependence on [H+]. The second order rate constant could be expressed in the form kII = k1 + k2(1 + KB[H+])−1. The kinetic data were found to be: Co(DH)2(py)Cl−k1 = 0.051 ±0.003 dm3 mol−1s−1, 0.051±0.003 dm3 mol−1 s−1,k2 = 0.76±0.04 dm3 mol−1 s−1 KB = 325±8 dm3 mol−1;Co(DH)2(py)Br-k1 = 0.071±0.004 dm3mol−1 s−1,k2 = 1.21±0.04 dm3 mol−1 s−1 KB = 460±15 dm3 mol−1; Co(DH)2(py)I-k1 = 0.075±0.006 dm3 mol−1 s−1,k2 = 1.91±0.09 dm3 mol−1 s−1 KB = 625±30 dm3 mol−1. The inverse dependence on [H+] suggests an inner-sphere mechanism involving protonated and unprotonated species of the complex. The order of rates for the three complexes was found to be Co(DH)2(py)I > Co(DH)2(py)Br > Co(DH)2(py)Cl.
Acid dissociation constants (pKa) of seven substituted benzoylacetanilides 1a-g and the stability constants (log Bn) of their 1:1 and 1:2 Fe(III) chelates were determined spectrophotometrically in 60% by volume ethanol-water mixture at ionic strength of 0.1 and 25°C. The correlations between log Bn and pKa and Hammett substituent constant (σ) were examined. The relations follow the equations: log B1 = 9.53−2.86 σ; log B2 = 16.27−7.07 σ; log B1 =1.26 pKa-2.36; and log B2=3.10 pKa-13.09. The relations between the stability constants of Fe(III) chelates with the ligands 1a-g and benzoylacetarylamides 2a-g and those reported for Cu(II) chelates with 2a-g are also discussed. The results imply that Fe(III) chelates with the ligands 1a-g are subject to “normal” rather than “structural” substituent effects.
New complexes of lanthanide perchlorates with 2-N-(pyridyl) benzamide (PyBA) of the type Ln(PyBA)3(ClO4)3 where Ln Y and LaYb have been synthesised and characterised by analyses, conductance, IR, 13C NMR (for diamagnetic complexes only) and electronic spectra. The molar conductance and IR data point to the ionic nature of the perchlorate groups in the complexes. IR data along with the 13C NMR data unequivocally proves that the coordination of the ligand to the metal ions taken place in a bidentate fashion through the oxygen of the benzamide group and the nitrogen of the heterocyclic ring. From a comparison of the visible electronic spectral shapes of the Nd3+, Ho3+ and Er3+ complexes with those reported in the literature, a 6-coordinate geometry around the metal ion has been assigned in all the complexes.
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