Coordination of perchlorate ion in the secondary solvation sphere of Am3+ in the tracer concentrations in mixed system of dimethyl sulfoxide/water with 1.00M (H,Na)(Cl,ClO4)

The stability constants, β₁, of monochloride complex of Am(III) have been determined in a mixed system of dimethyl sulfoxide (DMSO) and water at 1.00 mol·dm⁻³ ionic strength using solvent extraction. The values of β₁ in mixed DMSO+H₂O solutions decrease rapidly with an increase in the mole fraction of DMSO (X _s ) in mixed solvents and become negative ones, which is not in a definition of stability constant, inX _s >0.04. The variation of β₁ inX _s ≦0.02 was accounted for by the size-variation of the primary solvation sphere around Am(III), which was present as a solventshared ion-pair, and by a little effect due to an invasion (coordination) of ClO₄ ⁻ into the secondary solvation sphere of Am³⁺. On the other hand, it was concluded that the β₁ obtained by solvent extraction inX _s >0.02 was an apparent value, because of a large effect due to an invasion (coordination) of ClO₄ ⁻ into the secondary solvation sphere of Am(III).     

M2(hpp)4Cl2 and M2(hpp)4, where M = Mo and W: preparations, structure and bonding, and comparisons with C2, C2H2, and C2Cl2 and the hypothetical molecules M2(hpp)4(H)2

The reaction between M(2)Cl(2)(NMe(2))(4), where M = Mo or W, and Hhpp (8 equiv) in a solid-state melt reaction at 150 degrees C yields the compounds M(2)(hpp)(4)Cl(2) 1a (M = Mo) and 1b (M = W), respectively, by the elimination of HNMe(2) [hpp is the anion derived from deprotonation of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp]. Purification of 1a and 1b is achieved by sublimation of the excess Hhpp and subsequent recrystallization from either CH(2)Cl(2) or CHCl(3) (or CDCl(3)). By single-crystal X-ray crystallography, the structures of 1a and 1b are shown to contain a central paddlewheel-like M(2)(hpp)(4) core with Mo-Mo = 2.1708(8) A (from CH(2)Cl(2)), 2.1574(5) A (from CDCl(3)), W-W = 2.2328(2) A (from CDCl(3)), and M-N = 2.09(1) (av) A. The Cl ligands are axially ligated (linear Cl-M-M-Cl) with abnormally long M-Cl bond distances that, in turn, depend on the presence or absence of hydrogen bonding to chloroform. The quadruply bonded compounds M(2)(hpp)(4), 2a (M = Mo), and 2b (M = W), can be prepared from the reactions between 1,2-M(2)R(2)(NMe(2))(4) compounds, where R = (i)()Bu or p-tolyl, and Hhpp (4 equiv) in benzene by ligand replacement and reductive elimination. The compounds 2a and 2b are readily oxidized, and in chloroform they react to form 1a and 1b, respectively. The electronic structure and bonding in the compounds 1a, 1b, 2a, and 2b have been investigated using gradient corrected density functional theory employing Gaussian 98. The bonding in the M-M quadruply bonded compounds, 2a and 2b, reveals M-M delta(2) HOMOs and extensive mixing of M-M pi and nitrogen ligand lone-pair orbitals in a manner qualitatively similar to that of the M(2)(formamidinates)(4). The calculations indicate that in the chloride compounds, 1a and 1b, the HOMO is strongly M-Cl sigma antibonding and weakly M-M sigma bonding in character. Formally there is a M-M triple bond of configuration pi(4)sigma(2), and the LUMO is the M-M delta orbital. An interesting mixing of M-M and M-Cl pi interactions occurs, and an enlightening analogy emerges between these d(4)-d(4) and d(3)-d(3) dinuclear compounds and the bonding in C(2), C(2)H(2), and C(2)Cl(2), which is interrogated herein by simple theoretical calculations together with the potential bonding in axially ligated compounds where strongly covalent M-X bonds are present. The latter were represented by the model compounds M(2)(hpp)(4)(H)(2). On the basis of calculations, we estimate the reactions M(2)(hpp)(4) + X(2) to give M(2)(hpp)(4)X(2) to be enthalpically favorable for X = Cl but not for X = H. These results are discussed in terms of the recent work of Cotton and Murillo and our attempts to prepare parallel-linked oligomers of the type [[bridge]-[M(2)]-](n)().     

The solvolysis oftrans-[Co(4-Mepy)4Cl2]ClO4 in water: acetonitrile and water: dioxan mixtures

Summary The solvolysis of the title complex is slower in 0 to 70% v/v aqueous dioxan than in aqueous acetonitrile at 40, 45, 50 and 55° C, a fact that is attributed to the higher basicity and ionizing power of the latter solvent mixtures. The observed non-linearity for logk (solvolysis) versus 1/D plots was interpreted in terms of the relative stability of ground and transition state species. The calculated Gibbs free energy for transfer of the species in the transition state is consistent with the extreme stretching of the chlorinecobalt bond, a result which confirms the interchange dissociative mechanismI _d for the complex under study.     

Chlorine-photosensitized reactions in the Cl2 + O2 + 1,1,1,2-C2H2Cl4 system

The gas-phase photochlorination (λ = 436 nm) of the 1,1,1,2-C₂H₂Cl₄ has been studied in the absence and the presence of oxygen at temperatures between 360 and 420°K. Activation energies have been estimated for the following reaction steps: The dissociation energy D(CCl₃CHCl? O₂) ± (24.8 ± 1.5) kcal/mole has also been estimated from the difference in activation energy of the direct and reverse reactions The mechanism is discussed and the rate parameters are compared to those obtained for a series of other chlorinated ethanes.     

Apparent molar heat capacities and volumes of aqueous electrolytes at 25°C: Cd(ClO4)2, Ca(ClO4)2, Co(ClO4)2, Mn(ClO4)2, Ni(ClO4)2, and Zn(ClO4)2

We have used a flow calorimeter and a flow densimeter for measurements leading to apparent molar heat capacities and apparent molar volumes of aqueous solutions of Cd(ClO₄)₂, Ca(ClO₄)₂, Co(ClO₄)₂, Mn(ClO₄)₂, Ni(ClO₄)₂, and Zn(ClO₄)₂. The resulting apparent molar quantities have been extrapolated to infinite dilution to obtain the corresponding standardstate apparent and partial molar heat capacities and volumes. These latter values have been used for calculation of conventional ionic heat capacities and volumes.     

Electromotive-force studies of mixed electrolytes in mixed solvents. HCl+NH4Cl in methanol+water solvents at 25°C

Electromotive-force measurements of the cell Pt, H₂(g, 1 atm)|HCl(m₁), NH₄Cl(m₂), methanol(X%), Water(100–X)%|AgCl|Ag have been made at 25°C for m₁+m₂=1 mole-kg^–1 and X=0, 10, 20, 30, 40, and 50% methanol by weight. Hydrochloric acid obeys Harned's rule in aqueous solutions, but a quadratic term is required in the mixed solvents. The Harned coefficients for the acid vary with solvent composition, and this invalidates the applicability of Harned's method for estimating activity coefficients for single electrolytes in mixed solvents. This method is described and the reason for the inapplicability of the method is discussed in terms of ion-ion and ion-solvent interactions.     

The bridging bidentate perchlorato group in ReO3(ClO4), ReO3(ClO4Cl2O6 and Sb2Cl6(O)(OH)(ClO4), a vibrational analysis

Raman and infrared analysis of the new compounds: ReO3(ClO4), an ivory-white solid, and (ClO2)xReO3(ClO4)1+x (x < or = 1), an orange-red chloryl salt, showed that bridging bidentate [ClO4] and terminal ReO3 groups are present in both complexes. Vibrational data on [ClO4] in ReO3(ClO4) were compared to those obtained experimentally and by DFT calculation on a bridging bidentate [ClO4] in Sb2Cl6(O)(OH)(ClO4).     

Cm3+-F- interaction in a mixed system of methanol and water

The stability constants (b₁) of the monofluoro complex of Cm(III) have been determined in mixed solvents of methanol and water using the solvent extraction technique. The values of lnb₁ increase as the molar fraction of methanol (X_s) in the mixed solvent increases. The variation in the stability constants mainly depends on the solvation of F^- and slightly depends on both (1) the solvation of cations in connection with the complexation of CmF²⁺ and (2) the electrostatic attraction of Cm³⁺-F^-. The variation in lnb₁ for Cm(III) due to the effect of both (1) and (2) is similar to that for Sm(III). By variation of lnb₁ the coordination number in the primary hydration sphere (CN) of Cm(III) decreased from a value between CN = 9 and CN = 8 to CN = 8, at about X_s = 0.02. The X_s value of the inflection point of the CN for Cm is slightly lower than X_s = 0.06 for Sm(III) and X_s = 0.03 for Eu(III), previously obtained.     

Synthesis of the complex aluminum hydrides M+Al2H7 − (M+=Li,Na, K) and a study of their transformations

Conclusions When lithium, sodium, and potassium aluminum hydrides react with an ether solution of AlH₃ in the presence of crown ethers, complexes are formed that contain the Al₂H₇ ^– anion.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 969–971, May, 1987.     

On the variation of the stability constants of EuCl2+ in the mixed system of dimethyl sulfoxide and water

The effect of water-miscible alcohols and acetone on the extraction and separation of Cd and Zn chlorides by TOPO was systematically investigated. The maximum extraction of Zn chloride with 0.1 M TOPO decreases in the order: acetone>methanol>ethanol>2-propanol>2-butanol. For alcohols, the sequence of decreasing extractability is thus parallel to the order of their dielectric constants. This can be explained by the increase of HCl extraction by TOPO in the same direction. The presence of additives in the polar phase prevents the formation of a bulky white precipitate encountered during extraction of ZnCl₂ from pure aqueous solutions. A decrease of Cd chloride extraction was generally noticed in presence of additives; this is more noticeable for the longer chain alcohols. The highest separation factor (E for ZnCl₂ and CdCl₂ in 0.48M HCl is obtained from 30% methanol (13.8 compared to about 3.8 in absence of methanol) and from 10–20% acetone where it reaches 30.     

Synthesis and properties of an Au(III) complex with N-nitrosated ethylenediamine AuEn(ONNC2H4,NH2) (ClO4)2

Conclusions The feasibility of the isolation of an N-nitrosoamidated ethylenediamine product in an Au(III) complex has been demonstrated for the first time; this has previously been observed only in the case of Pt(IV) complexes. The compound was characterized by elemental analysis and by spectroscopic studies.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2654–2659, December, 1987.     

The solvolysis oftrans-[Co(4-Mepy)4Cl2]ClO4 in water-methanol mixtures

Summary The solvolysis of thetrans-[Co(4-Mepy)₄Cl₂]ClO₄ complex was studied in 0 to 70% v/v H₂O: MeOH mixtures at 40, 45, 50 and 55 °C. The high negative S^* values found for the complex cation under investigation, relative to that oftrans- [Co(py)₄Cl₂]⁺ reported in the literature, were attributed to the substituent methyl groups. The free energies of transfer of both the ground and the transition states were calculated from which the dominant effect of the solvent on the transition state is apparent.     

Syntheses,crystal structures and spectroscopic properties of the novel complexes [M(MOBPT)*2 (H2O)2](ClO4)2 · 4H2O (M = CoII and NiII)

The novel cobalt(II) and nickel(II) complexes with 4-(p-methoxyphenyl)-3,5-bis(pyridin-2-yl)-1,2,4-triazole (MOBPT) have been synthesized and their molecular structures determined by X-ray analysis, i.r. and by ESI-MS spectroscopy. The metal atom is in a distorted octahedral environment. Two bidentate chelating ligands (MOBPT) coordinate to the metal center equatorially and two water molecules coordinate axially. Each MOBPT entity coordinates via one triazole nitrogen and one pyridine nitrogen atom. Magnetic measurements show that the complexes are high-spin species in the 75–300 K range.     

Spectrochemical studies on the ethylthiourea complexes of palladium (II) and platinum (II): M2(Etu)2X4(X = Cl,Br, I) and M(Etu)4A2(A = Cl,Br, I,ClO4, BF4, CF3COO).

The ethylthiourea complexes of Pd(II) and Pt(II): M₂(Etu)₂X₄ (X = Cl, Br, I) and M(Etu)₄A₂ (A = Cl, Br, I, ClO₄, BF₄, CF₃COO) have been studied by i.r. and electronic spectra and the halide-bridged M₂(Etu)₂X₄ complexes by bridge-splitting reactions with nitrogen ligands. Ethylthiourea is S-coordinated to the metal. Far i.r. spectra show ν(MS) bands at 270–300 cm⁻¹ and, for the M₂(Etu)₂X₄ complexes ν(MX) bands corresponding to terminal and bridging MX bonds. From the electronic spectra of the Pd(Etu)₄A₂ (A = ClO₄, BF₄) complexes the Δ₁ ( = 22120 cm⁻¹) spectral parameter was obtained.     

A mononuclear manganese(III) complex of an asymmetric macrocyclic ligand with a ring contraction [MnHL2(ClO4)](ClO4) · 2.5H2O

The template reaction of sodium 2,6-diformyl-4-chlorophenolate and N,N-bis(2-aminoethyl)–hydroxyethylamine followed by in situ transmetallation of Mn(ClO₄)₂ results in a mononuclear manganese(III) complex of one 21-membered asymmetric 2:2 Schiff base macrocycle, in which a hydroxyethyl group of the amine has been eliminated and ring contraction at one chamber of the macrocycle has occurred to form an imidazolidine ring. An X-ray study indicates that the geometry about the manganese(III) ion is distorted octahedral. The electrochemical behavior of this complex in MeCN has been studied by cyclic voltammetry.     

Solubility in the system Na2Cr2O7 + 2NH4Cl ⇆ (NH4)2Cr2O7 + 2NaCl-H2O

The solubility in the water-salt quaternary reciprocal system Na₂Cr₂O₇ + 2NH₄Cl ⇆ (NH₄)₂Cr₂O₇ + 2NaCl-H₂O has been investigated for the first time at 25, 50, and 75°C. Using a formal analytical model, the boundaries of the phase fields have been determined, and the univariant lines and invariant points have been calculated. The experimental data have been used to calculate the temperature and concentration parameters of the circular isohydric process of potassium dichromate preparation with the participation of ammonium salts as intermediates.