Iodide ion complexes

In equations (24) through (29), hi/ h is shown to be the iodide ion-complexing constant of the cleavage transition state, +H. Similarly hl/ hi is the iodide ion-complexing constant of =HI. Since the iodide... 

Fig. 8. Three-dimensional representations showing the structural details of the human carbonic anhydrase C active site for (A) the native enzyme, (B) the enzyme-iodide ion complex, and (C) the enzyme-salamide complex. Taken from Ref. (47) with permission. The residues numbered 1—9 in (A) are believed to be solvent molecules (presumably water molecules). Residue 1 occupies the fourth ligand site in the inner coordination sphere of the active site zinc ion. The atomic positions (solid spheres) of the sulfonamide inhibitor, salamide, are indicated in (C)...

All of these complexes were characterized by multinuclear NMR ( H, C, "B, Hg) and fast atom bombardment mass spectrometry (FAB/MS). Monoanion complexes (8) and (9) form dianion complexes (11) and (12), respectively, on further treatment with the respective halides <92JA380>. Both monoanion and dianion complexes can undergo metathesis with [As(QH4)4]Cl to form products (13) and (14), respectively <91AG(E)1507,92JA380>. Uncomplexed cyclotetramer (1) was extracted from its iodide ion complexes (8) and (11) by Ag(OAc) in ethanol. The same reaction from bromide and iodide complexes resulted in incomplete extraction of host tetramer <92AG(E)893>. Uncomplexed host macrocycles (1) and (3) were characterized by H, C, and B NMR <92AG(E)893,93JAI93). 

A poly( -vinyl-2-pyrroHdinone)-iodine complex [25655-41-8] (PVP-iodine), has been used extensively in hospitals and elsewhere because of its germicidal, bactericidal, fungicidal, and generally disinfecting properties (150). It is sold as a solution that contains about 10% available, or active, iodine and about 5% inactive iodine, in the form of iodide ion (see Disinfectants and antiseptics Industrial antimicrobial agents). 

Silver Iodide. Silver iodide, Agl, precipitates as a yellow soHd when iodide ion is added to a solution of silver nitrate. It dissolves in the presence of excess iodide ion, forming an Agl2 complex however, silver iodide is only slightly soluble in ammonia and dissolves slowly in thiosulfate and cyanide solutions. 

It resembles tetracyanoethylene in that it adds reagents such as hydrogen (31), sulfurous acid (31), and tetrahydrofuran (32) to the ends of the conjugated system of carbon atoms suffers displacement of one or two cyano groups by nucleophilic reagents such as amines (33) or sodiomalononittile (34) forms TT-complexes with aromatic compounds (35) and takes an electron from iodide ion, copper, or tertiary amines to form an anion radical (35,36). The anion radical has been isolated as salts of the formula (TCNQ) where is a metal or ammonium cation, and n = 1, 1.5, or 2. Some of these salts have... 

Determination. To an aliquot of the silver(I) solution containing between 10 and 50 pg of silver, add sufficient EDTA to complex all those cations present which form an EDTA complex. If gold is present (>250 xg) it is masked by adding sufficient bromide ion to form the AuBr4 complex. Cyanide, thiocyanate or iodide ions are masked by adding sufficient mercury(II) ions to complex these anions followed by sufficient EDTA to complex any excess mercury(II). Add 1 mL of 20 per cent ammonium acetate solution, etc., and proceed as described under Calibration. 

Discussion. Iodine (or tri-iodide ion Ij" = I2 +1-) is readily generated with 100 per cent efficiency by the oxidation of iodide ion at a platinum anode, and can be used for the coulometric titration of antimony (III). The optimum pH is between 7.5 and 8.5, and a complexing agent (e.g. tartrate ion) must be present to prevent hydrolysis and precipitation of the antimony. In solutions more alkaline than pH of about 8.5, disproportionation of iodine to iodide and iodate(I) (hypoiodite) occurs. The reversible character of the iodine-iodide complex renders equivalence point detection easy by both potentiometric and amperometric techniques for macro titrations, the usual visual detection of the end point with starch is possible. 

Complexes with the Bromide and Iodide Ions. The few existing data on oromide complexes are assembled in Table VI. Data on iodide complexes are completely lacking. 

The complex that is formed can dissociate to form a cation (n-tr-complex) and an iodide anion, with the iodide ion reacting with the excess iodine molecules that are present. In addition the decomposition of the n-cr-complex can lead to the formation of highly reactive iodine cations, which can initiate further reactions — e.g. oxidations or electrophilic substitutions of aromatic systems [11, 13]. 

Substances containing active chlorine or bromine oxidize iodide ions — if necessary under the influence of UV light - to iodine, which reacts with starch to yield the well-known intense blue starch-iodine inclusion complex. 

However, with bromide and iodide ions the five-coordinate adducts [Pt(PPh3)2(CNCH3)2X]+ are isolated the bromide complex loses isocyanide slowly but the iodide complex is stable. The analogous reactions with [Pt(diphos)(CNCH3)2] give disubstitution. 

Treichel, Knebel, and Hess provided further data on these systems by studying reactions of [Pt(PRj)2(CNCH3)2] with various halide ions and with pseudohalides. A series of five-coordinate complexes were obtained from reactions with iodide ion (PRj = PPhj, PPh2Me, PPhMe2, PEtj), and a study was carried out to measure the stability of these complexes with respect to ligand loss 155). Stability constants for several of these complexes were obtained from spectroscopic data. Other reactants (Cl, Br, CN, SCN) generally yielded the appropriate [Pt(PRj)2(CNCH3)X] species, as expected. 

That is, the activated complex contains one Cr(V) atom and one Fe(II) atom. Espenson has shown, from a consideration of the induced oxidation of iodide ion, that the reaction between Cr(VI) and Fe(Il) requires one added proton. Consequently, the [H ] -dependence of the rate can be viewed as the addition of two protons in a pre-equilibrium followed by the addition of a further proton in the slow step, viz. 

The rate of oxidation with Ce(IV) perchlorate depends on the method of preparation . The material from certain preparations gives a deep red complex, containing two equivalents of Ce(IV) to one molecule of H2O2, which decomposes in second order fashion-presumably by means of two concerted one-equivalent oxidations of the substrate. Other preparations give no complex and decompose peroxide much faster. The difference is thought to lie in the degree of association of the oxidant cf. the Ce(IV) oxidation of iodide ion, p. 359). 

Rendleman, J. A. (2003). The reaction of starch with iodine vapor. Determination of iodide-ion content of starch-iodine complexes. Carbohydr. Polym. 51,191-202. 

H from C0, the commonest probably being 1,2-dehalogenations and, in particular, 1,2-debromination. This can be induced by a number of different species including iodide ion, I , metals such as zinc, and some metal ions, e.g. Fe2. The reaction with I in acetone is found to follow the rate law (after allowance has been made for the I complexed by the I2 produced in the reaction),... 

The synthesis of the Ni(n) complex of the 13-membered (anionic) macrocycle (78) is also achieved using an in situ procedure (Cummings Sievers, 1970) in which triethylenetetramine, acetic acid, acetylacetone, and nickel acetate are heated in water at the reflux. Addition of iodide ion and adjustment of the pH of the solution to approximately 10, leads to crystallization of the Ni(n) complex of the required cyclized product (78) as its iodide salt. The reaction type has been extended to include Cu(ii) as the template metal (Martin, Wei Cummings, 1972) and has also been... 

In an alternative synthetic procedure, the Ni(n) complex of the depro-tonated form of (81) undergoes rearrangement on heating in water (at 100°C) at pH 5 over 6 hours. Addition of iodide ion and adjustment of the pH to 10 results in precipitation of the corresponding macrocyclic complex (77) as its iodide salt. More recently, the related acid-catalyzed... 

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