Ruthenium complexes thiocyanates

The absorbance depends on the concentration of thiocyanate and the pH, and also on the time and temperature of heating of the ruthenium solution with thiocyanate. The ruthenium complex is formed quantitatively when the solution is heated for at least 10 min, with a thiocyanate concentration greater than 0.15 M and pH 0.5-3.5. At least a 15-fold molar excess of Capri Blue is necessary. 

Kalyanasundaram K., Gratzel M. Applications of functionalized transition metal con5)lexes in photonic and optoelectronic devices. Coord. Chem. Rev. 1998 77 347-414 Kamat P.V. Photoelectrochemistry in particulate systems. 3. Phototransformations in the colloidal TiOa-thiocyanate system. Langmuir 1985 1 608-611 Kamat P.V., Bedja I., Hotchandani S., Patterson L.K. Photosensitization of nanocrystalline semiconductor films. Modulation of electron transfer between excited ruthenium complex and SnOa nanocrystalUne with an externally applied bias. J. Phys. Chem. 1996 100 4900-4908 Kamat P.V., Vinodgopal K. Environmental photochemistry with semiconductor nanoparticles. Mol. Supramol. Photochem. 1998 2 307-350... 

The imidazole complex raras-[Ir(imid)2Cl4]- is stable for days in neutral aqueous solution, and for hours in the presence of added thiocyanate. Addition of silver nitrate precipitates the silver salt of the complex, with no indication of Ag+-catalyzed removal of coordinated chloride. Thus this iridium(III) complex is substitutionally much more inert than its much-studied (because (potentially) anti-tumor) ruthenium(III) analogue (96). 

The Ru redox potentials of the thiocyanate complexes were more positive (by 350 mV) than its corresponding dichloro complexes and show quasire-versible behavior. This is in good agreement with the Ligand Electrochemical Parameters scale, according to which the thiocyanate Ru wave should be 340 mV more positive than the dichloro species Ru° potential [56]. The ioJ ired peak current is substantially greater than unity due to the oxidation of the thiocyanate ligand subsequent to the oxidation of the ruthenium(II) center. 

Four osmium(IV) complexes have been reported. The salts [Os2N(NH3)8(NCS)2]Y3 (Y = Cl, NCS) are made from [Os2N(NH3)8C12)2+ and NCS. The IR and Raman spectra suggest that it contains N-bonded thiocyanate, 4 consistent with the probable harder nature of the Os,v2N3+ moiety (see also p. 563). It has recently been reported, however, that osmium and ruthenium can be separated via their [M(NCS)6]2 complexes using polyurethane foam.378... 

Ruthenium (osmium) is stripped from the organic solvent with 1 M H2SO4 in the presence of NaSCN, and the absorbance of the resulting ruthenium- (or osmium-) thiocyanate complex measured directly. 

The chloride-, bromide-, and thiocyanate complexes of ruthenium(IIl) and osmium(IV) can be extracted from acid solutions by oxygen-containing solvents, also in the presence of TBP or amines [10,12-15]. Osmium has been separated from Ru after conversion into Osle and extraction with TO A [16]. From mixtures of thiocyanate complexes of Ru and Os, only the Os complex can be extracted into diethyl ether containing a small amount of peroxide [14]. Poljmrethane foam has also been used for separating Ru and Os as their thiocyanate complexes [17,18]. 

The anionic thiocyanate complex of ruthenium(IIl), Ru(SCN)6, reacts with Capri Blue (basic oxazine dye, formula 4.31) to form a sparingly soluble ion-associate which precipitates at the phase boundary and on the wall of the separating funnel during shaking of the aqueous phase with DIPE. After separation, the ion-associate is dissolved in methanol and the absorbance of the solution is measured [41]. 

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