Thiocyanato complexes stability

The stepwise stability constants for zirconium and hafnium thiocyanato-complexes have been determined by solvent-extraction techniques. The values ) i = 12.1 2.2, = 215 11, P4. = 205 + 20 for zirconium, and Pi =... 

On the other hand, the reverse trends exhibited by Eu+2 and Fe+2 as reductants imply in part that we are gaining more from the increasing stability of the bond being formed as we go from Br to F than we are losing from the stability of the bond being broken. I think this is also pertinent to the question of comparison of azido and thiocyanato complexes. With Co(CN)fz as reductant, the stable form of the product complex is sulfur-bonded, so that the orientation of the ligand in the oxidant is favorable for remote attack on the sulfur end, whereas the situation is unfavorable for Cr+2 and Fe+2 as reductants. 

In the presence of excess TC, soft acidic Cd2+ forms tetra-thiocyanato complexes in which four TC coordinate to Cd2+ with their soft basic S atoms as expected from the high stability constant of complex formation. 

The new Reinecke-salt-like compounds K[Cr(NCS)4L ] (n = 1 or 2 L = o- or m-phenylenediamine, respectively) have been prepared by the reaction of K3[Cr-(NCS)6] with L and their thermal stabilities investigated.179 Diquinolino- and di-iodoquinolino-silver(i) iodide salts of the anions [Cr(NCS)6]3- and [Cr(NCS)4L2] (L = aniline, o- or p-toluidine) have been prepared and characterized.180 Chro-mium(m) thiocyanato-complexes with biguanide derivatives, K[Cr(NCS)4L] [L = phenyl-, p-chlorophenyl-, tolyl-, or 1-(p-chlorophenyl-5-isopropyl)biguanide], have been prepared by the reaction of K3[Cr(NCS)6] with L in anhydrous EtOH and their i.r. and electronic spectra reported.181 cis- and trans-[Cr(en)2(NH3XNCS)]2 + have been prepared and both shown to have a Amax value at 476 nm, but with the expected relative magnitudes of s values, cis > trans, as 120 to 80.182 The thermal decompositions of the salts [Cr(NH3)6 x(NCS)x](NCS)3 x (x = 0. 1. or 2) have been characterized. Under d.t.a. conditions [Cr(NH3)6](NCS)3 changes stepwise to [Cr(NH3)5(NCS)](NCS)2, trans-[Cr(NH3)4(NCS)2](NCS), and finally to merfac-[Cr(NH3)3(NCS)3].183... 

Indium Halides.—Compositions of halogeno- and thiocyanato-complexes of In in DMSO have been determined potentiometrically at 25 °C, and stability constants have been calculated.566... 

Relatively little work has been done on the redox reaction between thallium and halide/pseudohalide ions (75, 93, 97,110, 328-330). Let us consider the qualitative order of stability of thallium(III) in the form of TlXp " complexes, where X = Cl, Br, I, SCN, CN, Thallium(III) forms strong complexes with all these ligands on the other hand, it can oxidize the X ions to X2. It is well known that the thallium(III) chloride complexes are perfectly stable for an indefinite period of time. The corresponding bromide complexes are usually stable, but at low Br/Tl ratios Tl(III) can be reduced by Br the reduction is easily prevented by adding excess of bromine. The iodo and thiocyanato complexes are approximately equally unstable toward redox reaction Tl(III) is rapidly reduced by the anion.Finally, the cyano complexes... 

K. The stability of the nitrato complex does not change at higher temperatures, but those of the chloro and thiocyanato complexes decrease moderately this results in negative values. This observation is the opposite to what was observed in... 

Apparent stability constants for In thiocyanato-complexes have been shown to include stability constants of hydroxo- and mixed thiocyanato-hydroxo-indium(m) complexes. The stability constant of the 1 1 thiocyanato-complex is only truly constant at pH ca. 1. ... 

Thallium(i) chloro-, thiocyanato-, and chloro(thiocyanato)-complexes have been studied potentiometrically (using a T1 amalgam electrode) at 10, 25, 40, and 60 °C. Thermodynamic stability constants were calculated at these temperatures. Enthalpies and entropies of formation of TlCl, T1(NCS), and TlCl(NCS)- were evaluated from the temperature dependence of the stability constants. ... 

This situation was slightly different for the cyano and the thiocyanato complexes, where the mesophase stability increased considerably compared to the halo compounds. In fact. X-ray diffraction suggested rather strong interactions between gold atoms (6.5 A) in addition to a smaller stacking period of 3.3 A, particularly for the SCN complex. Thus, the columnar structure remained basically the same, but was tighter, consistent with the greater mesophase stability. 

The stability of Am complexes in many cases is similar to that of complexes of lanthanides of equal ionic radius. In some cases (where bonding may presumably involve f electrons) the stability of the Am " complex is slightly greater than that of the corresponding lanthanide complex [300]. As discussed earlier, this difference in stability can be used to effect a separation of Am from lanthanide elements. The properties of Am chloride and thiocyanato complexes are particularly useful for this latter purpose. Ion-exchange studies [61, 296, 301] with both anion resins and long-chain amine hydrohalides show that Am in concentrated LiCl and HCl solutions forms anionic chloride complexes. 

A method for the stabilization of the isocyano metabolites by formation of rhodium complexes has been developed. The (r 5-pentamethylcyclopentadienyl)- or (r 5-ethyltetramethylcyclopenta-dienyl)-di- i-thiocyanato rhodium complexes of the isocyanides (eg 129) normally provide stable, crystalline compounds, thus facilitating the analysis and the purification of these metabolites [139,140]. 

Four chiral homologous complexes were also prepared. None of the palladium complexes showed mesomorphic properties, whereas a monotropic chiral discotic nematic phase was observed for the platinum complex (Table 18). The absence of mesomorphism for the dinuclear palladium complexes may be due to the type of chiral chain used, which differed from that used for the platinum system. All of the complexes form charge-transfer complexes with TNF. A Colh phase was induced for the two halo-bridged palladium complexes and for the platinum complex, as was observed for their non-chiral analogs. Flowever, the chiral nematic phase of the platinum compound was suppressed. At low TNF content, a chiral Nq phase was stabilized for the thiocyanato-bridged compound along with a non-chiral No phase at higher concentration. 

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