Some analytical applications of aromatic sulfonyl haloamines: Determination of thiocyanate and cyanide ions in metal complexes and salts with bromamine-B and dichloramine-B

Simple, rapid, and reproducible methods for the determination of thiocyanate and cyanide ions in metal salts and complexes with bromamine-B (BAB) and dichloramine-B (DCB) have been developed. The oxidation involves eight and two electron changes, respectively, with NCS^? and CN^? ions in 0.05–0.20 N NaOH medium in the case of BAB and in partially aqueous medium with DCB. The proposed methods could be employed for computing the number of thiocyanate and cyanide ligands present in the respective metal complexes.     

Some analytical applications of aromatic sulfonyl haloamines: Determination of thiosemicarbazide alone and in its metal complexes with bromamine-B and dichloramine-B

Simple, rapid, and reproducible back titration methods for the determination of thiosemicarbazide (TSC) in free state and in Zn, Cd, Hg, Ni, Pt, and Pd metal complexes with bromamine-B (BAB) and dichloramine-B (DCB) have been developed. The oxidation reaction involves a 12-electron change per TSC molecule in 0.2–1.0 M NaOH and water-acetic acid media with BAB and DCB, respectively. The proposed analytical procedures for the assay of TSC are also useful for computing the number of TSC ligands present in the respective metal complexes. The two aromatic sulfonyl haloamines used, BAB and DCB, were prepared and then characterized by ¹³C FT-NMR spectral data.     

Some analytical applications of aromatic sulfonyl haloamines: Estimation of indigocarmine by chloramine-B,bromamine-T,and dibromamine-T

Sodium N-chlorobenzenesulfonamide (chloramine-B, CAB), sodium N-bromo-p-toluenesulfonamide (bromamine-T, BAT) and N,N′-dibromo-p-toluenesulfonamide (dibromamine-T, DBT) are employed as analytical reagents for estimating indigocarmine (IC) in solution. A four-electron stoichiometry is observed within 30 min in the following media: CAB, 0.1–1.0 N HCl or H₂SO₄ and pH 1 buffer; BAT, 0.01–0.10 N NaOH; DBT, glacial acetic acid. The back titration methods are fairly rapid, simple, and accurate. The product of oxidation, isatinsulfonate, was estimated by spectrophotometric measurements at 410 nm. The sulfonamides formed by reduction of the haloamines are detected by TLC and paper chromatography.     

N,N-Dibromobenzenesulfonamide as an analytical reagent: Determination of thiocyanate and cyanide ions in metal complexes and salts and thiosemicarbazide alone and in its metal complexes

Simple, rapid, and reproducible analytical procedures, for determining thiocyanate and cyanide ions in metal salts and complexes and thiosemicarbazide (TSC) in the free state and in its metal complexes, with the new oxidant, dibromamine-B (DBB), have been proposed. These procedures are also useful for computing the number of ligands present in the complexes. With DBB, CN⁻, and NCS⁻ ions and TSC undergo stoichiometric oxidations with 2-, 8-, and 12-electron changes per ion or molecule, respectively, in water-acetic acid medium. The reagent DBB has been prepared and characterized by elemental analyses and ir and FT-NMR-¹H and -¹³C spectral data.     

Determination of thiosemicarbazide alone and in its metal complexes with arylhalosulfonamides

The behavior of 10 arylhalosulfonamides as oxidimetric analytical reagents toward thiosemicarbazide (TSC) alone or in its metal complexes has been critically examined and general procedures for its estimation have been developed. The proposed analytical techniques are simple and reproducible. These procedures are also useful for computing the number of TSC ligands present in the complexes. The oxidation involves twelve-electron change per TSC molecule with all the oxidants. The complexes have been prepared and characterized by elemental analyses and IR spectra.     

Determination of cyanide,thiocyanate, cyanate,hexavalent chromium,and metal cyanide complexes in various mixtures by ion chromatography with conductivity detection

The first aim of this study was to develop a selective, sensitive, and reliable method for direct simultaneous determination of cyanate, thiocyanate, and hexavalent chromium by ion chromatography (IC) with conductivity detection. The other target was to successfully determine cyanides by utilizing same chromatographic system. Yet, since cyanides can not be detected by the direct method, free cyanide ions were converted into cyanate with chloramine-T at alkaline pH. In addition, strongly complexed metal cyanides were converted into cyanate by using photo-oxidation following chloramine-T. Total cyanate ion obtained from developed methods were analyzed with IC. The chromatographic separations on anion exchange column were accomplished by optimized multistep gradient eluent program using NaOH as the eluent. Proposed method was applied for the simultaneous determination of cyanide and hexavalent chromium in electroplating bath solutions and in industrial wastewater. Cyanide and hexavalent chromium could be measured in the linear dynamic ranges of 0.6–961.5 and 0.9–118.5 µmol L^?1, respectively. The limit of detection and limit of quantification of cyanide were 0.18 and 0.61 µmol L^?1, and these values for chromium(VI) were 0.26 and 0.86 µmol L^?1, respectively.     

Studies on complexes of 4-(2-thiazolyl)thiosemicarbazide with some bivalent metal ions

Summary The 4-(2-thiazolyl)thiosemicarbazide HTTSC, reacts with metal ions to yield two types of complex M(HTTSC)₂ Cl₂ [M=cobalt(II), nickel(II) copper(II), cadmium(II), or mercury(II)] and [M(TTSC)₂] [M=cobalt(II), nickel(II) or copper(II)]. These complexes have been characterized by elemental analyses and studied by magnetic and spectroscopic techniques. Tetrahedral coordination around cadmium(II) and mercury(II), square planar geometry around cobalt(II) and nickel(II) in [Co(TTSC)₂] and [Ni(HTTSC)₂]Cl₂, respectively, and octahedral stereochemistry for the remaining complexes is proposed.     

Estimation of cyanide ion in metal salts and complexes by means of chloramine-T and dichloramine-T

A simple and accurate method for the estimation of cyanide in salts and complexes is based on oxidation with chloramine-T (in pH 4 buffer) or dichloramine-T (in presence of acetic anhydride). The oxidation involves a two-electron change. Halides interfere with the estimation of KCN, but the interference can be eliminated by precipitating and determining zinc cyanide. A method for estimating KCN and KCNS in mixtures is also described.     

Anion-exchange separations of metal ions in thiocyanate media

The analytical potential of a weak-base macroreticular anion-exchange resin for the quantitative separation of metal ions in thiocyanate media is investigated and demonstrated. Distribution data are given for the sorption of some 25 metal ions from aqueous mixtures of potassium thiocyanate (1.0M or less) and 0.5M hydrochloric acid. The magnitude of the distribution data suggests many possible separations, some of which were quantitatively performed by procedures which are fast, simple and require only mild conditions. Representative separations are removal of traces of iron(III) and copper(II) from water samples prior to the determination of water hardness (calcium and magnesium), separation of nickel(II) from vanadium(IV) and the separation of thorium(IV) from titanium(IV). Some multicomponent separations are the separation of rare earths(III) and thorium(IV) from scandium(III) and the separation of rare earths(III) from iron(III) and uranium(VI).     

Determination of thiocyanate with aromatic halosulphonamides in acid and alkaline media

Ten organic aromatic halosulphonamides, both mono and dihalo compounds, ranging from chlorosulphonamides to iodosulphonamides, have been prepared and characterized by their infrared and NMR spectra and successfully used for determining thiocyanate in its metal salts and complexes. The proposed procedures are simple, rapid and reproducible, with an error of about +/-0.8%. These procedures are also useful for computing the number of thiocyanate ligands present in the complexes. Comparison of the present results with those from the argentometric method shows excellent agreement. The oxidation involves an 8-electron change per thiocyanate ion with the chloro and bromosulphonamides and a 6-electron change with iodosulphonamides.     

Ab initio structure and vibrational frequencies of lithium aromatic sulfonyl imide salts

The structure and vibrational frequencies of an aromatic lithium sulfonyl imide, i.e., lithium bis(4-nitrophenylsulfonyl)imide (LiNPSI) has been studied using self-consistent ab initio Hartree–Fock and hybrid density functional methods. These calculations engender two linkage isomers, which correspond to the local minima on the potential-energy surface. In the lowest-energy isomer, the ligand binds to the metal ion through two oxygens, one from each of the different SO₂ groups on the central nitrogen and forms a six-membered ring. Another LiNPSI isomer, wherein the anion coordinates through oxygen and nitrogen atoms and which is 55.9 kJmol⁻¹ higher in energy, has also been obtained. The S–N–S bond angle in the free anion as well as in the LiNPSI complex turns out to be nearly 121°. A comparison of the vibrational spectra of the free NPSI anion and that of the LiNPSI complex reveals that the SO₂ stretching vibrations at 1,239 and 1,205 cm⁻¹ can be used to differentiate between the two linkage isomers of the complex. The stronger complexation ability of the NPSI anion, compared to that for (CF₃SO₂)₂N⁻ has been explained in terms of the charge density within the molecular electrostatic potential isosurface encompassing both SO₂ groups of the anion. Received: 20 February 2002 / Accepted: 25 March 2002 / Published online: 3 June 2002     

Determination of cyanide and thiocyanate by a spectrophotometric flow-injection method

A rapid spectrophotometric flow-injection method is described for the determination of cyanide and thiocyanate. The method involves a two-step procedure in which the total concentration of both species is first determined (using sodium isonicotinate/sodium barbiturate reagents), after which the cyanide is complexed with nickel(II) and thiocyanate is quantified separately; the cyanide concentration is calculated by difference. Various parameters such as pH, temperature and nickel concentration were optimized. The method is applied to synthetic sample solutions and the results are compared with those obtained by the ASTM distillation method. The limits of detection for cyanide and thiocyanate are 0.05 and 0.08 μg ml^?1, respectively, with a sample throughput rate of 10 h^?1.     

NNS tridentate thiosemicarbazide and 1,3,4-thiadiazole-2-amine complexes of some transition metal ions: syntheses,structure and fluorescence properties

The reactions of Zn(II), Mn(II), and Ni(II) acetates with 1-picolinoyl-4-phenyl-3-thiosemicarbazide (Hppts) yielded [Zn(ppts)₂]·CHCl₃ (3), [Mn(ppts)₂]·THF (4), and [Ni(ppts)₂]·THF (5), respectively, but HgCl₂ gave a cyclized product N-phenyl-5-(pyridin-2-yl)-1,3,4-oxadiazole-2-yl-amine (2). The treatment of Hppts with conc. H₂SO₄ formed N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-yl-amine (1). Hppts is a nonfluorescent material, but 3, 4 and the cyclized products 1,3,4-oxadiazole/1,3,4-thiadiazole are fluorescent. The cyclized ligand N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-amine (1) formed [Zn(2-Hppt)₂(OAc)₂] (6) and [Cd₂(2-Hppt)₂(OAc)₂(μ-OAc)₂] (7) in which Cd(II) has a binuclear acetate-bridged seven coordinate pentagonal bipyramidal geometry. Complex 7 is also a fluorescent material with maximum emission at 425 nm at an excitation wavelength of 254 nm.     

Determination of iron and cyanide in cyanoferrate complexes

A simple method of destroying cyano-complexes and of analysing for both iron and cyanide in a single sample of a cyanoferrate complex is proposed.     

Polarographic studies of complexes of cadmium with chloride and thiocyanate ions in aqueous medium

This is a polarographic study of the system Cd(II)?NaCl?NaSCN in aqueous medium of a constant ionic strength of μ=1.0 M with NaClO₄. Reduction takes place through a reversible bielectronic process. The diffusion magnitudes I_d and D have been determined, and the formation of the mixed complexes CdClSCN, [CdCl₂SCN]^? and [CdCl(SCN)₂]^?, with stability constants of β₁₁=106±101² mol^?2, β₂₁=156±101³ mol^?3 and β₁₂=484±801³ mol^?3, respectively, has been demonstrated. The values of these constants are discussed in the light of statistical aspects and Watters equations.     

Methylphenylphosphinate complexes with tri- and tetra-positive metal ions

Summary A series of methylphenylphosphinate {mpp; [-O-P-Ph(Me)-O-]^–} complexes of the forms M(mpp)₃ (M = Al, Ga, In, Sc, Y, Dy, Ti, V, Cr and Fe) and M(mpp)₄ (M = Th or U) were made from the appropriate metal chloride and a large excess of MeO(Me)PhP(O) at elevated temperatures. Structures involving linear, ligand-bridged polymeric species are suggested on the basis of the i.r. and magnetic data.     

Some electrochemically generated elemento-organicradical ions and metal complexes as studied by esr

ESR spectra have been obtained for the radical anions Ph_nEl^XXX , where El = P, Si or As, and also for substituted nitrobenzenes. Radical anions were generated by electrochemical reduction within a microwave cavity. The nature and stability of radical ions and other paramagnetic species were established by the investigation of the electrochemical behaviour of the substances. The spin density distribution shows that atoms of the elements in Ph_nEl^XXX are not to be taken as “isolating bridges”. Spin density distributions have also been established for other radical ions.Paramagnetic complexes Mo^V and W^V have been prepared by electrochemical reduction of appropriate molybdenum and tungsten compounds and their structure and magnetic parameters have been established.     

Sequential flow-injection determination of cyanide and weak metal—cyanide complexes with flow-through heterogeneous membrane electrodes

Free cyanide and cyanide present in weak complexes are determined by using two flow- through silver iodide/silver sulphide electrodes with an intervening gas diffusion unit. Under optimal conditions, the linear range is 10^?5?10^?3 mol dm^?3 cyanide, and the relative standard deviations are ca. 2%, with a sampling rate of 20 h^?1. Total cyanide can be determined in the presence of Zn(II), Cu(II) and Cd(II) but results are low with Ni(II), Co(II) or Fe(III) present. Sulphide and thiocyanate must be absent.