In The Iron Research Articles

ChemInform Abstract: POLAROGRAPHIC STUDIES OF SOME METAL(II)‐THIOCYANATE COMPLEXES IN ACETONITRILE

Chemischer InformationsdienstVolume 5, Issue 37 Organoelement Compounds ChemInform Abstract: POLAROGRAPHIC STUDIES OF SOME METAL(II)-THIOCYANATE COMPLEXES IN ACETONITRILE SEIZO MISUMI, SEIZO MISUMISearch for more papers by this authorMAKOTO AIHARA, MAKOTO AIHARASearch for more papers by this authorSETSUKO KINOSHITA, SETSUKO KINOSHITASearch for more papers by this author SEIZO MISUMI, SEIZO MISUMISearch for more papers by this authorMAKOTO AIHARA, MAKOTO AIHARASearch for more papers by this authorSETSUKO KINOSHITA, SETSUKO KINOSHITASearch for more papers by this author First published: September 17, 1974 https://doi.org/10.1002/chin.197437341Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue37September 17, 1974 RelatedInformation

Polarographic Studies of Some Metal (II)-Thiocyanate Complexes in Acetonitrile

Abstract The formation of thiocyanate complexes of cadmium (II), copper(II), cobalt(II), and iron(II) has been studied in acetonitrile by polarographic, conductometric, and spectrophotometric methods. The values of overall stability constants were found to be; logβ4=19.7 for [Cd(SCN)4]2−, logβ2=7.6 for [Cu(SCN)2]− and logβ4=15.5 for [Co(NCS)4]2−. The reaction between copper(II) species and mercury metal was investigated and the electrode reaction was estimated. Kinetic current for cobalt(II)-thiocyanate complex was observed and the rate constant for the dissociation of the complex was obtained. The rate constant of reduction in the iron(II)-thiocyanate system was determined to be 1.9×10−3 cm/s by cyclic voltammetry.

Iron(II)-chloramine-T reaction

When a large excess of the oxidant is used in the iron(II)—chloramine-T reaction at pH 2·56–5·6 the amount of oxidant consumed is well above the stoichiometric amount required to oxidize iron(II) to iron(III). This has been attributed to the formation and subsequent behaviour of free radicals during the reaction. The formation of free radicals has been experimentally demonstrated. They apparently dimerize to give products of the type RNClNClR (R = CH 3C 6H 4SO 2), which are further oxidized by chloramine-T. The dimerized species liberate iodine very slowly from acidified potassium iodide. This explanation satisfactorily accounts for the observed extent and rate of destruction of excess of chloramine-T in presence of small amounts of Fe(II) or bromide at pH 2·65–4·70. The storage of chloramine-T in metal containers might cause extensive destruction of the oxidant by a similar free radical mechanism and should be avoided.

Linkage isomerism of the sulfate ion in ditoluenesulfinato-bis(2,2′-bipyridyl) complexes of iron(II), cobalt(II), and nickel(II)

Linkage isomers involving the O- and S-bonded unidentate sulfinate ions were prepared. The isomers are of the type [M(bipy) 2(RSO 2) 2] where R = p-toluene and the metal = Fe II, Co II, and Ni II. In the iron(II) compounds, S-bonded sulfinate effects spin-pairing. Thus, Mössbauer spectra of the iron(II) O-bonded (Ia) and S-Bonded (Ib) isomers show, at 259°K, quadrupole splittings ΔE Q = 2.65 and 0.31 mm/sec and isomer shifts δ IS = +0.99 and +0.31 mm/sec, for Ia and Ib, serially. These values are characteristic for 5T 2 and 1A 1 ground states in iron(II) consistent with the magnetic moments, at 292°K, of μ eff = 5.27 and 0.95 BM in Ia and Ib, respectively. From the electronic dd spectra of nickel(II) O-bonded (IIa) and S-bonded (IIb) isomers, the average values 10Dq = 10,200 and 11,600 cm −1 as well as β 35 = 1.03 and 0.97 were obtained for IIa and IIb, serially. In the O-bonded cobalt(II) isomer (IIIa), 10Dq = 11,025 cm −1 and β 35 = 0.84, whereas only the a 4T 1→ 4T 2 transition has been observed in the S-bonded isomer (IIIb) giving the estimate 10Dq∼12,300 cm −1. The magnetism of IIa,b and IIIa,b is consistent with six-coordinated nickel(II) and cobalt(II), respectively. The consequences with regard to the position of the unidentate O- and S-bonded sulfinate ion in the spectrochemical and nephelauxetic series are discussed.

Steric hindrance to the formation of metal complexes of 2-chloro-1,10-phenanthroline

2-Chloro-1,10-phenanthroline (L) readily accepts one proton on the 10-nitrogen atom and in strongly acidic media a second proton on the 1-nitrogen atom. Stoicheiometric acid dissociation constants p K 1 H=4.27 and p K 2 H=0.22 for the species HL + and H 2L 2+ were obtained from spectrophotometric measurements in aqueous buffers at 25° and I=0.1 M(KCl). Partition coefficients were determined for the uncharged base between water and n-hexane, carbon tetrachloride, and chloroform, and the stepwise formation constants of metal complexes were obtained from similar measurements with salt solutions. Stabilities increased in the order Fe<Co<Cu > Zn and, when due account is given to differences in ligand basicities, steric hindrance to complex-formation is about the same as that due to a 2-methyl substituent. In the iron(II) complex, K 3 #62; K 1, K 2, an anomaly previously found only with 2,2'-bi-pyridine and 1,10-phenanthroline.

Metal complexes with azine ligands. I. Ligand hydrolysis and template synthesis in the iron(II)-2-Pyridinaldazine system

The dinuclear iron(II) complex of 2-pyridinaldazine, Fe 2(PAA) 3 4+, has been shown to undergo conversion in aqueous solution to the more stable Fe(PAA) 2 2+ by a 3-step process involving initial dissociation of one metal ion, followed by hydrolysis of the three ligand molecules to give the tris-pyridinalhydrazone complex, and finally recondensation of two aldhehyde fragments to give the bis-tridentate complex. Geometric considerations show that the ligand must exist in different geometric isomers in the initial and final compounds. It is proposed that the metal ion acts as a template for formation of the less stable ligand isomer in Fe(PAA) 2 2+. Spectrophotometric evidence is presented to support the existence of the 3:2 complex ion in solution and to show that this ion is stabilized in solutions of high ionic strength. As part of the evidence for the above sequence of reactions, a model 3:1 iron(II) complex was synthesized from the new azine ligand 2-pyridinalbenzaldazine.

Some theoretical and practical problems in the use of organic reagents in chemical analysis—VII: Investigations of the transition metal complexes of pyridine-2-aldoxime

The composition of the mononuclear pyridin-2-aldoxime complexes of 3 d 5–3 d 10 transition metals formed in neutral solution were determined. The successive stability constants of the manganese (II), cobalt (II), nickel (II) and zinc (II) complexes were measured. It was proved by proton resonance measurements that in the iron (II) and cobalt (II) complexes pyridine-2-aldoxime is a strong field ligand, and the nickel (II) complex is octahedral.