Iodide lead complexes

The selectivity of the Pb reaction with PAR can be increased by the use of cyanide, which efficiently masks Ag, Cd, Hg, Cu, Ni, Co, and Zn. Another way to improve the selectivity is to use a preliminary isolation of lead. Extraction as the iodide complex is a convenient method for its separation from interfering metals. Before this operation, Fe(III) and some other metals can be separated by extraction as thiocyanate complexes. Then potassium iodide is added, the HCl concentration adjusted, and the iodide-lead complex extracted with MIBK. Besides lead, the extract should contain only cadmium (see the procedure below). However, in the preliminary extraction from thiocyanate medium, about 15% of the lead present is also extracted [4]. 

Sensitive methods for lead include a number based on ion-associates formed by the anionic iodide-lead complex and the basic dyes, such as Malachite Green (benzene, e = 8.0-10 ) (58,59], Brilliant Green (59], Ethyl Violet [59], fuchsin (formula 27.1) (extraction with benzene-cyclohexane from 0.2 M H2SO4, e = 2.0-10 at 560 nm [60], and cyanine dyes [61]. In the method involving the antipyiine dye Chrompyrazole I (formula 23.1), the pseudo-solution formed is stabilized with the non-ionic surfactant OP-10 [62]. 

Electrochemical properties of samarium(ii) iodide are very sensitive to the nature of solvents. Reduction potential increases by replacing THE with a more polar solvent, such as DME or CH3CN. Addition of HMPA to a THE solution of samarium(ii) iodide leads to a substantial increase in the electron-donating nature of samarium(ii). The principal samarium(ii) species in a mixed solvent of THE and HMPA is an ionic cluster of [Sm(HMPA)4(THE)2] 2I in HMPA-THF (4 1) or [Sm(HMPA)6] 2I in HMPA-THE (>10 1). The reactivity order of the samarium(ii) complexes is [Sm(HMPA)6] 2I > [Sm(HMPA)4(THF)2] 2P > Sml2 in the reaction with 1-iodobutane. 

Cations having a tetracoordinate silicon may appear by three general routes. Apart from the ionization of a silicon-reactive ligand bond, the cations can be formed by transformation of a group bound to silicon, in particular by the addition of positively charged ion. For example, the quaternization of trimethylsilylamine with methyl iodide leads to the same ionic complex as the reaction of trimethylsilyl iodide with trimethylamine [Eq. (46)] (254). 

Note Reaction of the dimethyl palladium(U) carbene complex with excess methyl iodide leads to decomposition of the compound by reductive elimination of an imidazolium salt that remains pendant on the phosphane anchor [283]. 

Allylation of a-thio-35), a-seleno-35) and a-silyl- 35,77) cyclopropyllithiums was not very successful35) but addition at —78 °C of 0.5 equivalent of copper (I) iodide-dimethylsulfide complex 35,106, W7> prior to the allylhalide leads 35,106,107) to a very high yield of homoallyl cyclopropyl sulfides or selenides (Scheme 24). Similar observations have been made on cyclobutyl derivatives3S). It is not clear at present whether a cuprate is involved in the process but we have evidence ( Se-NMR) that a new species is transiently being formed, at least in the seleno series. The synthesis of homoallyl cyclopropylsilanes was also reported 78) and involves the allylation of a postulated cuprate formed by the addition of lithium dibutyl cuprate to a-lithiocyclopropylsilane (Scheme 26). 

The used of cationic cyclopalladated species or iodide-containing complexes increases the reactivity of the Pd-C bond and leads to spontaneous depalladation reaction... 

A monoclinic form of the Cu iodide pyridine complex has been prepared but unlike the cubane tetrameric modification, this isomer does not show luminescence thermochromism. The photochemistry of copper(n) chloride has been examined at 313 nm and 77 K in ethanol and HCl solution and has shown transient radical complex formation between Cu and CH3CHOH. Photolysis of DMF solutions of [CuClJ " is reported to lead to formation of the radical,CH2(CH3)NCHO, (10) and the Cu -(10) complex. At higher concentrations of [CuClJ ", photooxidation of (10) by excited [CuClJ predominates. The photochemistry of the... 

The closely related aromatic N—S bidentate 2-aminobenzenethiol (H2NC6H4SH) forms complexes with VO , Cr , Mn , Fe", Co", Ni", Ni , Cu and Zn", and (I o", Co " and Pd". Again, reaction of [Ni(SC5H4NH2)2] with methyl iodide leads to S-methylation of the coordinated ligands, whereas oxidation in strongly alkaline solution yields a dark blue Ni complex of formula... 

Allylation of a-thio- , a-seleno- and a-silyl- cyclopropyllithiums was not very successful but addition at —78 °C of 0.5 equivalent of copper (I) iodide-dimethylsulfide complex prior to the allylhalide leads to a very... 

Cobalt (II) iodide is subject to auto complex formation in TMP and it is ionized in TMP, DMF, DMA and DMSO. Nickel iodide is completely ionized in TMP and DMS02. Tin(IV) iodide, bismuth(III) iodide, antimony(III) iodide, lead(II) iodide and cadmium (II) iodide are considerably ionized in DMF and completely ionized in DMSO. ... 

Recently, it was demonstrated that a small amount of copper(I) iodide-phenanthroline complex efficiently catalyzes aromatic tiifluoromethylation of 2-iodothiophenes 38 and 102 leading to 2-trifluoromethylated products 78 and 103 in 75-85 % yields [64]. 

The reactivity of these group 4 metal complexes has been studied to some extent. Starting from complex [(6)MCl2], the reaction with nucleophiles such as alkylhthium led to the classical reactivity at M-Cl (Scheme 32) [89]. The reactions with strong electrophiles such as isocyanates, carbon dioxide, or carbodiimide did not show the expected insertion into the M=C bond, but rather a [2+2] cycloaddition. The basicity and nucleophilicity of the C center was proved by reactions with aromatic amines, phenols, aliphatic alcohols, or methyl iodide leading to the 1,2 addition product. 

The Turing mechanism requires that the diffusion coefficients of the activator and inlribitor be sufficiently different but the diffusion coefficients of small molecules in solution differ very little. The chemical Turing patterns seen in the CIMA reaction used starch as an indicator for iodine. The starch indicator complexes with iodide which is the activator species in the reaction. As a result, the complexing reaction with the immobilized starch molecules must be accounted for in the mechanism and leads to the possibility of Turing pattern fonnation even if the diffusion coefficients of the activator and inlribitor species are the same 62. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

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