Complexes molar conductivity

Complex Molar conductivity (S) Number of ions indicated Present formulation... 

In aqueous electrolyte solutions the molar conductivities of the electrolyte. A, and of individual ions, Xj, always increase with decreasing solute concentration [cf. Eq. (7.11) for solutions of weak electrolytes, and Eq. (7.14) for solutions of strong electrolytes]. In nonaqueous solutions even this rule fails, and in some cases maxima and minima appear in the plots of A vs. c (Eig. 8.1). This tendency becomes stronger in solvents with low permittivity. This anomalons behavior of the nonaqueous solutions can be explained in terms of the various equilibria for ionic association (ion pairs or triplets) and complex formation. It is for the same reason that concentration changes often cause a drastic change in transport numbers of individual ions, which in some cases even assume values less than zero or more than unity. 

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

Iron(III) complexes have also been prepared with 2-acetylpyridine N-phenylthiosemicarbazone [142], 14. Three have been formulated as square pyramidal [Fe(14-H)A2] (A = Cl, NCS and NOj) based, in part, on molar conductivities of 37-62 ohm cm mol . Their ESR spectra in frozen DMF are essentially the same as for other Af-substituted species, which likely indicates the presence of [FeL2] ions. More recently [138], [Fe(14-H)2]C104 has been isolated and its solid ESR spectrum is reported to be axial with g > g - Table 1 summarizes the g-values of iron(III) heterocyclic thiosemicarbazone complexes. 

Besides complexes of thiosemicarbazones prepared from nitrogen heterocycles, iron(III) complexes of both 2-formylthiophene thiosemicarbazone, 26, and 2-acetylthiophene thiosemicarbazone, 27, have been isolated [155]. Low spin, distorted octahedral complexes of stoichiometry [Fe(26)2A2]A (A = Cl, Br, SCN) were found to be 1 1 electrolytes in nitromethane. Low spin Fe(27)3A3 (A = Cl, Br, SCN) complexes were also isolated, but their insolubility in organic solvents did not allow molar conductivity measurements. Infrared speetra indicate coordination of both via the azomethine nitrogen and thione sulfur, but not the thiophene sulfur. The thiocyanate complexes have spectral bands at 2065, 770 and 470 cm consistent with N-bonded thiocyanato ligands, but v(FeCl) and v(FeBr) were not assigned due to the large number of bands found in the spectra of the two ligands. 

The molar conductance values of the complex Ln(DPSO)6 I3 in acetonitrile are slightly higher than those suggested for 1 1 electrolytes, due to the displacement of some coordinated iodide by the solvent (250). The conductance values observed for the complexes, however, approach more closely the values reported for 1 1 electrolytes as the ionic size of the lanthanide ion decreases. This may be due to the increasing strength of the metal-anion bond with decreasing cation size. 

Complexes of the type Ln(TMSO)3 Cl3 are nonelectrolytes in nitromethane, indicating the coordination of all the chloride ions to the lanthanide ion (262). In methanol, however, these complexes behave as 1 1 electrolytes. The variation of molar conductance values with concentration of the Dy(III) complex in methanol was studied. The data indicate that at higher concentrations the complex behaves as a nonelectrolyte while at lower concentrations dissociation sets in and the complex behaves as a 1 1 electrolyte. 

Table 2. Molar conductance (A) for the hexachloride and the hexaisothio-cyanate complexes of the lanthanides in nitrobenzene 35, 36)...

Perchlorate ion complexes, 28 255-299 with cobalt group metals, 28 265-268 coordination types, 28 256-260 with copper group metals, 28 273-283 with early transition metals, 28 260-263 electronic spectra. 28 258-259 ESR spectra, 28 260 infrared and Raman spectra, 28 257-258 with iron group metals, 28 263-265 with lanthanides, 28 260-265, 287-288 magnetic susceptibility, 28 260 molar conductivities, 28 260 with nickel group metals. 28 268-273 X-ray crystal structure analysis, 28 256-257... 

Scheme 1). In addition to the determination of molar conductivity, magnetic moment, and IR spectra, the complex was characterized by X-ray structural analysis (4). This indicates that the cationic complex with neutral H2dapsox is symmetrically coordinated as a pentadentate ligand. Co(II) occurs in a PBP environment with water and methanol molecules in apical positions (Fig. 1). Although the side chains are symmetrically coordinated, Co-O(eq) bond lengths differ significantly. 

I2]. The substantial solubilities of these compounds in chloroform and other less polar organic solvents are in agreement with their formulation as nonelectrolytes. In methanol at 25° C., the molar conductivities of 166 and 167 ohm-1 for [Ni-(NH2CH2CH2S-CH3)2I2] and [Ni(NH2CH2CH2S-CH2C6H5)2I2], respectively, are characteristic of di-univalent electrolytes in this solvent, indicating almost complete solvolysis of the coordinated iodide ions in this relatively polar solvent. Decomposition of these complexes was observed upon dissolving in water. Visible and near-infrared spectra results are also consistent with structure VI. 

Analytical data on the soluble products isolated from chloroform are in excellent agreement with the composition 1 Ni+2 1 monoalkylated ligand 1 I or Br. The magnetic moment of this methylated complex was found to be 1.89 Bohr magnetons per nickel (II). The molar conductivities of the methylated and benzylated complexes in methanol at 25° C. are 75.4 and 68.4 ohm-1, respectively. These values approximate those expected for uni-univalent electrolytes in this solvent. The formulation of these alkylated compounds as dimeric electrolytes (structure VII) does not appear to be totally consistent with their physical properties. One or both halide ions may be bound to the metal ion. These results lead to the easily understood generalization that terminal sulfur atoms alkylate more readily than bridged mercaptide groups. 

Heterobinuclear complexes containing alkali or alkaline earth metal cations have been derived from mononuclear transition metal complexes of compartmental ligands (51).288 The molar conductivities of the (51)-CuLi2 series suggest that the complexes are uniunivalent electrolytes in water and so are present in solution as Li[(51b)CuLi]- H20 the corresponding di-sodium, -potassium or -cesium complexes are unibivalent electrolytes and so likely to be present in solution as M2[(51)Cu]- H20. 

Use of silver nitrate and only a small excess of trimethyl phosphite also gave rise to an exothermic reaction in this case AgL2N03 was isolated.193 The low conductivity of this complex in acetone and its IR spectrum in the nitrate region suggested the presence of coordinated nitrate. In acetone, it was found to be monomeric and only poorly conducting. The structure was expected to contain a bidentate nitrate. In acetonitrile, dissociation was evident due to the 10-fold increase in molar conductivity. 

Kundu and Bhattacharya14 have isolated dioxouranium complexes of benzohydroxamic acid with the compositions M[U02(C7H602N)3] [where M = Li, Na, K, Cs, Tl, N4, pyH+ (pyridinium) or agH+ (aminoguanidinium)] and M [U02(C7H602N)3]2 [where M = enH2+ (ethylene-diammonium)]. All the complexes, with the exception of the sodium compound, are insoluble in common organic solvents but are soluble in DMSO and DMF. The complexes have been characterized on the basis of electronic, IR and molar conductance data in DMF. Their fairly stable character is indicated by thermogravimetric analysis and the stability order is NH4+ < Tl+ < Cs+ < Li+ w Na+ agH+ < K+ pyH+ < enHl+. 

As far as the determination of the composition of the complex is concerned, this can be obtained from the variation of electrical conductance of an ionic solution titrated with a solution of the neutral receptor as a result of the different mobilities of the species in solution. Plots of molar conductances, Am, against the ratio of the concentrations of the receptor and anion can provide useful information regarding the strength of anion-receptor interaction. In fact, several conclusions can be drawn from the shape of the conductometric titration curves. 

The temperature dependence of molar conductivity, calculated from ionic conductivity determined from complex impedance measurements and molar concentrations, and the VFT fitting curves are shown Figure 5.8. The VFT equation for molar conductivity is... 

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