Copper -thiourea complex

As with all immersion metal systems, the copper needs to be perfectly clean and textured before the tin plating step. A predip is used to main tain proper chemical balance in the tin bath and prevent contamination. The tin deposition is not a direct galvanic displacement, since tin is more electronegative than copper. Thiourea is used in tin chemical formulation to create a copper-thiourea complex on the surface. This complex becomes more electronegative than tin, and then participates in the immersion reaction. Because of the need to drive the reaction, the tin bath contains relatively high concentrations of chemicals, which must be thoroughly rinsed. Waste treatment of the system is comphcated due to high levels of thiourea. 

Localized deposits containing copper and copper oxides demand a high local concentration of thiourea, and if an inadequate excess of thiourea is present to complex the cuprous ion, precipitation of the insoluble, white copper-thiourea monochloride salt may occur. 

There also exists a considerable number of ionic tris(thiourea) complexes. Thiourea is capable of reducing copper(II) salts to copper(I) complexes in acid solution to form [Cu(thiourea)3] salts. The following have been isolated chloride (194, 195), nitrate (194), oxalate (194, 195, 298), monohydrogen arsenate, and phosphate (298). 

Copper complexes of thioureas and N-substituted thioureas have also been suggested to account for the effectiveness of the parent compounds as antitubercular agents [537]. On the other hand, Ueno [538] suggested that the parent thioureas acted by removing copper from some M. tuberculosis copper-dependent enzyme and that the antitubercular activity was dependent on the relative stabilities of the enzyme complex and thiourea complex. However, the activities of two series of N-substituted (2-pyridyl and 4-pyryl) thioureas [539] could not be correlated with copper complex stability [540]. 

N.q.r. data have been reported for a range of copper(i) complexes of thiourea and some substituted thioureas. The structure of [Cu4 SC(NH2)2 io] (SiFg)2,H20 has been determined and the complex consists of six-membered rings of alternating copper and sulphur atoms connected by sulphur bridges to form chains which are in turn interconnected via a four-membered CU2S2 ring to form a three-dimensional polymer. ... 

Haram et al. [385] described a detailed system for the synthesis of CuS nanoparticles using a copper-ammonia complex (pH=l 1) and thiourea in separate microemulsions formed by a non-ionic surfactant (e.g. Triton X-100) with 2-methylpropan-l-ol as co-surfactant and cyclohexane as the oil phase. Other nonionic surfactants used were NP-4, NP-7 and NP-9.5 (nonylphenyl ether surfactant series) the only ionic surfactant used was sodium dodecyl sulfate (SDS). The reactions envisaged were... 

In methylthiourea complexes with metals such as platinum, palladium, copper, zinc, and cadmium the amide band appears in a range from 1565 to 1580 cm S which is shifted from its normal position at 1550 cm in methylthiourea In thiourea complexes of platinum, palladium, zinc, and nickel the band appears between 1625 and 1615 cm compared to 1610 cm in thiourea [ ]. In boron halide complexes of acetamides the band appears in the 1555-1525 cm range [ ]. In trifluoroacetamides the band appears in almost the same positions as in the corresponding acetamides, near 1580 cm ... 

The copper complex is very stable at neutral pH, but it fades very rapidly in the presence of hydrogen ions. Other complex formers such as tartaric acid or citric acid and thiourea interfere with the reaction and, therefore, should not be included in mobile phases used for the separation of amino acids [3]. 

Complexing, using a complexing agent such as thiourea or ammonia, for example, to remove mixtures of cuprous oxide, cupric oxide, and plated copper metal. 

From the first of the two reactions shown, it can be seen that in the acid cleaning solution the cupric ion (Cu2+) is formed from cupric oxide. The thiourea component then reduces the cupric ion to the cuprous ion (Cu+) and, in a series of reactions, complexes it, essentially preventing the cupric ion from ultimately plating out as copper. 

As the overall concentration of copper and copper oxides in the boiler deposit increases, however, less thiourea is required. This is because, as ferric ions are generated during the iron oxide dissolution process, they oxidize the plated copper, which can then be removed from the boiler by forming a complex with thiourea. Conversely, if ferric ions are not generated, the plated copper remains and no complexing can take place. 

The behavior of thiourea towards copper(II)-chloro complexes in acetone exemplifies the major changes in redox properties provoked by back-donation, as copper (I) and free chlorine are produced 50—52). The back-donation of copper(II) towards the sulfur atom of the thiourea ligand leads to a substantial decrease in electron population at the metal ion. Compensation is effected by the exercise of the EA function of copper towards coordinated chlorine until the electronic properties of copper and chloride approach those of copper (I) and chlorine (0) respectively ... 

Thiourea masks Cu2+ by reducing it to Cu+ and complexing the Cu+. Copper can be liberated from thiourea by oxidation with H202. Selectivity afforded by masking, demasking, and pH control allows individual components of complex mixtures of metal ions to be analyzed by EDTA titration. 

In the preceding iron determination, the results would be about 10% high because serum copper also forms a colored complex with ferrozine. Interference is eliminated if neocuproine or thiourea is added. These reagents mask Cu+ by forming strong complexes that prevent Cu+ from reacting with ferrozine. 

Ammonium bifluoride, when used at 0.5%, is also useful in assisting the removal of magnetite-based deposits. Add 2 to 3% thiourea where copper is present. The use of excess thiourea [CS(NH2>2] complexes dissolved copper and prevents it from plating out on steel surfaces and causing an equivalent amount of iron to dissolve. The heat exchanger must be thoroughly flushed out to remove all traces of copper and also inspected. 

An X-ray study of [Cu(phen)(thiourea)I], probably the complex previously identified as Cu(phen)(thiourea)2I, has shown the copper to be essentially tetrahedrally co-ordinated with a N2SI donor set.638... 

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