The Recently Synthesized Dimagnesiabutadiene and the Analogous Dimetalla‐Beryllium, ‐Calcium, ‐Strontium,and ‐Barium Compounds

The 2014 synthesis of the remarkable dimagnesium compound Mg₂[C₄(CH₃)₂(Si(CH₃)₃)₂](C₃H₇)₂(C₄H₈O)₂ may point the way to a new chapter in alkaline earth organometallic chemistry. Accordingly, we have studied the known Mg compound and the analogous Be, Ca, Sr, and Ba structures. Although most of our theoretical predictions come from density functional methods, the latter have been benchmarked using coupled cluster theory including single, double, and perturbative triplet excitations, CCSD(T) using cc‐pVTZ basis sets. Among our most important predictions are the energies for dissociation to the butadiene plus the RM?MR [R=(C₃H₇)₂(C₄H₈O)₂; M=Be, Mg, Ca, Si, and Ba] entities. The most reliable predictions for the dissociation energies are 99–104 (Be), 85–93 (Mg), 90–99 (Ca), 83–92 (Sr), and 83–94 (Ba) kcal mol^?1. Thus, there is reason to anticipate that the four unknown compounds should be achievable synthetically. The predicted metal–metal distances (not single bonds) are 2.89 Å (Mg???Mg), 3.46 Å (Ca???Ca), 3.75 Å (Sr???Sr), and 4.04 Å (Ba???Ba). The separated RM?MR compounds have longer M?M distances but genuine metal–metal single bonds. This perhaps counter intuitive result is due to the presence of the bridging carbons in the alkaline earth butadiene compounds. All five compounds incorporate metal–carbon ionic interactions.     

Coordination chemistry of the alkaline earth metal ions with Zwitterionic forms of the Schift bases. X-Ray studies and other spectroscopic properties

The non-ionized forms of tetradentate Schiff bases NN′-ethylenebis(salicylideneimine), H₂L and NN′-propane-1,3-diylbis(salicylideneimine), H₂L′ react with hydrated alkaline earth halide and nitrate to give complexes of the type: M(H₂L)Cl₂·nH₂O [M = Mg(II), Ca(II), Sr(II); n = 0–4], M(H₂L)₂Cl₂ [M = Ca(II), Sr(II), M(H₂L)_nBr₂ [M = Ca(II), Sr(II); n = 2, 3 and Mg₂(H₂L)₃Br₄], M(H₂L)_nI₂ [M = Mg(II), Ca(II), Sr(II), Ba(II); n = 2, 3)], M(H₂L)_n(NO₃)₂ and M(H₂L′)_n(NO₁)₂[M = Mg(II), Ca(II);n = 1, 2)]. Because of distinct spectral similarities with structurally known Ca(H₂L′)(NO₃)₂ compound, the Schiff bases are coordinated through the negatively charged phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups, which carry the protons transferred from phenolic groups on complexation. Halide and nitrate are coordinated to the central metal ion except in 2:1 nitrato complexes where the presence of both ionic and coordinated nitrate groups are evident and also in 3:1 halide complexes where the presence of non-coordinated halide cannot be excluded. X-Ray powder photographs showed no marked similarities between Ca(H₂L′)(NO₃)₂ and Mg(H₂L′)(NO₃)₂ while there are some isomorphic features between the same types of halide complexes. Infrared spectra and other structural information revealed the polymeric nature of the complexes. Therefore the coordination numbers exhibited by the alkaline earth metal cations would be 4, 6 or 8 in these series of Schiff base complexes.     

Extraction behavior of U(IV) from nitric acid medium using di-isodecyl phosphoric acid dissolved in dodecane

Solvent extraction of U(VI) with di-isodecyl phosphoric acid (DIDPA)/dodecane from nitric acid medium has been investigated for a wide range of experimental conditions. Effect of various parameters including nitric acid concentration, DIDPA concentration, temperature, stripping agents, and other impurities like rear earths, transition metal ion, boron, aluminum ion on U(VI) extraction has been studied. The species extracted in the organic phase is found to be UO₂(NO₃)(HA₂)·H₂A₂ at lower acidity (<3.0 M HNO₃). Increase in temperature lead to the decrease in extraction with the enthalpy change by ∆H = −16.27 kJ/mol. Enhancement in extraction of U(VI) from nitric acid medium was observed with the mixture of DIDPA and tri butyl phosphate (TBP). The stripping of U(VI) from organic phase (DIDPA–U(VI)/dodecane) with various reagents followed the order: 4 M H₂SO₄ > 5% (NH₄)₂CO₃ > 8 M HCl > 8 M HNO₃ > Water. High separation factors between U(VI) and impurities suggested that the use of DIDPA for purification of uranium from multi elements bearing solution.     

Extraction and extraction chromatographic separation of minor actinides from sulphate bearing high level waste solutions using CMPO

Bench-Scale studies on the partitioning and recovery of minoractinides from the actual and synthetic sulphate-bearing high level waste (SBHLW) solutions have been carried out by giving two contacts with 30% TBP to deplete uranium content followed by four contacts with 0.2M CMPO+1.2M TBP in dodecane. The acidity of the SBHLW solutions was about 0.3M. In the case of actual SBHLW, the final raffinate contained about 0.4% -activity originally present in the HLW, whereas with synthetic SBHLW the -activity was reduced to the background level.¹⁴⁴Ce is extracted almost quantitative in the CMPO phase,¹⁰⁶Ru about 12% and¹³⁷Cs is practically not extracted at all. The extraction chromatographic column studies with synthetic SBHLW (aftertwo TBP contacts) has shown that large volume of waste solutions could be passed through the column without break-through of actinide metal ions. Using 0.04M HNO₃>99% Am(III) and rare earths could be eluted/stripped. Similarly >99% Pu(IV) and U(VI) could be eluted.stripped using 0.01M oxalic acid and 0.25M sodium carbonate, respectively. In the presence of 0.16M SO ₄ ^2– (in the SBHLW) the complex ions AmSO ₄ ⁺ , UO₂SO₄, PuSO ₄ ²⁺ and Pu(SO₄)₂ were formed in the aqueous phase but the species extracted into the organic phase (CMPO+TBP) were only the nitrato complexes Am(NO₃)₃·3CMPO, UO₂(NO₃)₂·2CMPO and Pu(NO₃)₄·2CMPO. A scheme for the recovery of minor actinides from SBHLW solution with two contacts of 30% TBP followed by either solvent extraction or extraction chromatographic techniques has been proposed.     

Thermal studies and decomposition kinetics of alkaline earth metal trichloroacetates

Alkaline earth metal trichloroacetates M(O₂CCCl₃)₂·nH₂O, where M = Be (1), n = 4; M = Mg (2), n = 6; M = Ca (3) or Sr (4) or Ba (5), n = 4, were synthesized and their thermal behavior analyzed using thermogravimetric analysis (TG/DTG/DSC). A critical examination was made for the apparent activation energy by means of non-isothermal kinetic methods employing multiple heating rates. A systematic and comparative study of thermal decomposition was carried out at different heating rates i.e., 5, 10, 15, and 20 °C min^?1 for various trichloroacetates synthesized. It was observed that the Ca, Sr, and Ba trichloroacetates decompose preferentially to respective metal halides while Be and Mg compounds decompose to metal and metal oxide, respectively. The composition of the final residues was also confirmed using FT-IR spectroscopy. The activation energy follows the order: Mg > Ca > Sr > Ba, Be being the exception. Results reveal that each metal trichloroacetate decomposes through its unique thermolysis mechanism.     

Photolysis of alkaline-earth nitrates

Peroxynitrite and nitrite ions are the diamagnetic products of photolysis (with light at a wavelength of 253.7 nm) of alkaline-earth nitrates; the paramagnetic products and hydrogen peroxide were not found. The structural water in alkaline-earth nitrate crystals did not affect the qualitative composition of the photodecomposition products. The quantum yield of nitrite ions was 0.0012, 0.0038, 0.0078, and 0.0091 quanta^?1 and that of peroxynitrite ions was 0.0070, 0.0107, 0.0286, and 0.0407 quanta^?1 for Sr(NO₃)₂, Ba(NO₃)₂, Ca(NO₃)₂ · 4H₂O, and Mg(NO₃)₂ · 6H₂O, respectively.     

Gamma-ray induced decomposition of some divalent and trivalent nitrates

Gamma-ray induced decomposition of some divalent nitrates, viz. Mg(NO₃)₂·6H₂O, Ca(NO₃)₂·4H₂O, Sr(NO₃)₂, Ba(NO₃)₂, Zn(NO₃)₂·6H₂O, Cd(NO₃)₂·4H₂O, Hg(NO₃)₂·2H₂O, Mn(NO₃)₂·4H₂O, Cu(NO₃)₂·3H₂O and trivalent nitrates, viz. Al(NO₃)₃·9H₂O, Fe(NO₃)₃·9H₂O, Cr(NO₃)₃·9H₂O, Y(NO₃)₃·6H₂O, In(NO₃)₃·3H₂O, La(NO₃)₃·6H₂O, Ce(NO₃)₃·6H₂O, Pr(NO₃)₃·6H₂O, Bi(NO₃)₃·5H₂O has been studied in solid state at room temperature. G(NO ₂ ^– ) values (after applying appropriate dose correction) have been found to vary in the range 0.12–3.16 and 0.069–2.15 for divalent and trivalent nitrates respectively. G'-values were calculated by dividing G by the ratio of number of electrons in nitrate ion to the total number of electrons in the nitrate salt. Cation size, its polarizing power, available free space in the crystal lattice and the number and location of water molecules seem to play a dominant role in radiolytic decomposition. For Zn, Sr, In, La and Ce nitrates dose variation studies have been carried out.     

Solid state photodecomposition of alkaline earth tris/malonato/ferrates/III/

Solid state photolysis of alkaline earth tris/malonato/ferrates/III/, i.e., M₃[Fe(CH₂C₂O₄)₃]₂.xH₂O /M=Mg, Ca, Sr, Ba/ has been investigated employing Mössbauer, infrared and reflectance spectroscopic techniques. The complexes were irradiated for 400 h using a medium pressure mercury vapour lamp of 250 Watts. Photoreduction led to the formation of M[Fe^II(CH₂C₂O₄)₂(H₂O)₂]. The extent of photoreduction showed the following order: Ca>Sr>Mg>Ba. The results have been compared with those of analogous alkaline earth tris/oxalato/ferrates/III/.     

Synthese,Struktur und Reaktivität der Erdalkalihydrogensulfate des Mg,Ca, Sr und Ba

Synthesis, Structure, and Reactivity of the Alkaline Earth Hydrogen Sulfates of Mg, Ca, Sr, and Ba The pure compounds of Ba(HSO₄)₂, Sr(HSO₄)₂ and Mg(HSO₄)₂ were prepared and identified as real hydrogensulfates. In contact with moist air Mg(HSO₄)₂ forms the monohydrate Mg(HSO₄)₂ · H₂O which can be dehydrated into Mg(HSO₄)₂ at about 120°C. The hydration of Mg(HSO₄)₂ proceeds crystallographically oriented. The unit cell parameters and the d-values of the new compounds were determined. Ba(HSO₄)₂ and Sr(HSO₄)₂ cristallize orthorhombic, Mg(HSO₄)₂ monoclinic and Mg(HSO₄)₂ · H₂O triclinic. Sr(HSO₄)₂ is isotypic in regard to Ca(HSO₄)₂. The relationship between the crystal structures and the chemical properties of the earth alkaline sulfates are discussed.     

Raman studies of molten salt hydrates: the beryllium and aluminium nitrate-water systems

Raman spectra of the liquid systems Be(NO₃)₂ · 20H₂O, Be(NO₃)₂ · 4H₂O, Al(NO₃)₃·20H₂O, and Al(NO₃)₃ · 9H₂O have been recorded. The spectra are analysed in terms of vibrational modes arising from water, the nitrate ion, the aquated metal ions and hydrolysis products. For the concentrated beryllium system, though not for the aluminium system, the spectra suggest a significant degree of proton transfer from [Be(OH₂)₄]²⁺ to NO₃^?. Solvent-separated metal-nitrate ion pairs appear to be present in all the systems studied.     

Extraction of pertechnetate anion as a ligand in metal complexes with tributylphosphate

The extraction of the pertechnetate anion has been investigated in the systems tributylphosphate (TBP)—solvent (carbon tetrachloride, n-heptane, chloroform)—metal salt (uranyl nitrate and chloride, thorium nitrate)—ammonium salt. In the absence of a metal, the solvates HTeO₄. iTBP (i=4) are extracted, while in the presence of uranium and thorium, the distribution of technetium corresponds to the formation of the mixed complexes: UO₂(NO₃)(TeO₄)·2TBP, UO₂Cl(TcO₄)·2TBP and Th(NO₃)₃ (TcO₁)·2TBP. The effective constants of the reactions H⁺+TcO ₄ ⁻ +i(TBP)_org←(HTcO₁·iTBP)_org, and (ML_n·2TBP)_org+TcO ₄ ⁻ ←(ML_n−1TcO₄·2TBP)_org+L were established in the above systems. The extraction of pertechnetate ion is more effective when it is coordinated to a cation solvated by TBP than the extraction in the form of pertechnetate acid solvated by TBP.     

The Valence Orbitals of the Alkaline-Earth Atoms

Quantum chemical calculations of the alkaline-earth oxides, imides and dihydrides of the alkaline-earth atoms (Ae=Be, Mg, Ca, Sr, Ba) and the calcium cluster Ca₆H₉[N(SiMe₃)₂]₃(pmdta)₃ (pmdta=N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) have been carried out by using density functional theory. Analysis of the electronic structures by charge and energy partitioning methods suggests that the valence orbitals of the lighter atoms Be and Mg are the (n)s and (n)p orbitals. In contrast, the valence orbitals of the heavier atoms Ca, Sr and Ba comprise the (n)s and (n−1)d orbitals. The alkaline-earth metals Be and Mg build covalent bonds like typical main-group elements, whereas Ca, Sr and Ba covalently bind like transition metals. The results not only shed new light on the covalent bonds of the heavier alkaline-earth metals, but are also very important for understanding and designing experimental studies.     

Zur Kenntnis der Hydrate des Typs MX2 · 1 H2O mit M = Sr,Ba und X = Cl,Br, I. Kristallstrukturen des Strontiumchlorid-Monohydrats,SrCl2 · 1 H2O,und des Strontiumbromid-Monohydrats,SrBr2 · 1 H2O

On Hydrates of the Type MX₂ · 1 H₂O with M = Sr, Ba and X = Cl, Br, I. Crystal Structures of Strontium Chloride Monohydrate, SrCl₂ · 1 H₂O, and Strontium Bromide Monohydrate, SrBr₂ · 1 H₂O The structures of SrCl₂ · 1 H₂O, orthorhombic, Pnma, a = 1088.1(1), b = 416.2(1), c = 886.4(1) pm, Z = 4, d_c = 2.92 Mg m^?3, R = 0.052 for 755 reflections, and of SrBr₂ · 1 H₂O, orthorhombic, Pnma, a = 1146.4(1), b = 429,5(1), c = 922.9(1) pm, Z = 4, d_c = 3.88 Mg m^?3, R = 0.056 for 762 reflections have been determined from a Patterson synthesis and refined by Fourier and Least Squares methods. The structure consists of [SrX₂ = H₂O]_n-layers normal to [100] and Sr? H₂O? Sr? H₂O-chains parallel [010]. The Sr? O distances are 265.1(3) pm, SrCl₂ · 1 H₂O, and 265.9(4) pm, SrBr₂ · 1 H₂O. The shortest Sr? Cl and Sr? Br distances (298.9(1) and 315.3(1) pm) are within the layers. The environment of oxygen and strontium is a distorted tricapped trigonal prism. The orientation of the water molecules has been determined from vibrational spectroscopic measurements. The hydrogen atoms H₁ and H₂ form bifurcated hydrogen bonds of different strength to neighbouring halide ions. The corresponding O···X distances are 331.9(4) and 320.2(4) pm, SrCl₂ · 1 H₂O, and 340.8(4) and 333.8(4) pm, SrBr₂ · 1 H₂O. The other O? X distances are between 310.3(5) and 323.7(5) pm, SrCl₂ · 1 H₂O, and 323.5(5) and 333.2(6) pm, SrBr₂ · 1 H₂O.     

Über Tetraiodomercurate des Calciums und Strontiums

On Tetraiodomercurates of Calcium and Strontium Tetraiodomercurates MHgI₄ · 8 H₂O (M ? Ca, Sr) as yellow crystals are obtainable by crystallization from aqueous solutions. Both compounds are not isotype in spite of consisting isolated [M(OH₂)₈] cations and tetrahedral [HgI₄] anions which are cubic closed packed. In the structure of the tetragonal CaHgI₄ · 8 H₂O (a = 13.972(3) Å; c = 18.155(4) Å; Z = 8; P4₂/mbc) are dodecahedral [Ca(OH₂)₈] cations, but antiprismatic [Sr(OH₂)₈] groups in the orthorhombic compound SrHgI₄ · 8 H₂O (a = 9.616(3) Å; b = 10.610(3) Å; c = 17.731(4) Å; Z = 4; Pcmn). The relations between both structure concerning a tetragonal “Aristotype” are discussed.     

Behavior of nitrite forms of nitrosylruthenium on extraction and back extraction of heterometalic Ru/Zn complexes with trioctylphosphine oxide

The state of ruthenium in conjugated phases upon extraction of trans-[Ru(¹⁵NO)(¹⁵NO₂)₄(OH)]^2? complex with tri-n-octylphosphine oxide (TOPO) in the presence of Zn²⁺ and subsequent back extraction with H¹⁵NO₃ and NH₃(concd.) solutions was studied by ¹⁵N NMR. Binuclear complexes [Ru(NO)(NO₂)_5?n (μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ] and [Ru(NO)(NO₂)_4?n (ONO)(μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ], where n = 2, 3, are predominant forms in extract. Kinetic restrictions for ruthenium extraction with TOPO solution in hexane and its back extraction with aqueous solutions of nitric acid and ammonia are eliminated in the absence of direct coordination of extractant to ruthenium. fac-Dinitronitrosyl forms [Ru(NO)(H₂O)₃(NO₂)₂]⁺, [Ru(NO)(H₂O)₂(NO₂)₂(NO₃)]⁰ (3 and 6 M HNO₃) and [Ru(NO)(H₂O)(NO₂)₂(NO₃)₂]^? (6 M HNO₃) prevail in nitric acid back extracts. Equilibrium constant at ambient temperature (0.05 ± 0.01) was assessed for the coordination of second nitrate ion to nitrosylruthenium dinitronitrato complex. Complex species [Ru(NO)(NO₂)₄(OH)]^2? and [Ru(NO)(NO₂)₃(ONO)(OH)]^2? prevail in ammonia back extract.     

Analytical application of embelin

Summary Embelin is reported as a new reagent for gravimetric estimation of (1) uranium in pure solutions at p_H 6.0–6.5 and (2) thorium in acid solutions of 0.4 N HCl. In both cases, the precipitates were ignited and weighed as U₃O₈ and ThO₂. The separation of thorium from large excess of uranium and rare earths could also be effected employing this reagent. In addition, Cu, Cd, Ca, Ba, Sr, Al, Be, Mn, Mg and Zn do not interfere.     

Applcation of the Pitzer equations to the solubility of ternary aqueous nitrate solutions at 25°C

The solubilities of the ternary systems Cu(NO₃)₂–Ca(NO₃)₂–H₂O and Cu(NO₃)₂–Mg(NO₃)₂–H₂O at 25°C were calculated from the solubility data for the binary systems by using the Pitzer equations. The calculated solubility isotherms were confirmed experimentally. The activity coefficients of the components, the osmotic coefficient, and the activity of water were calculated from the experimental isotherms.     

Extraction of U(VI) by cyanex-272

Extraction of U(VI) from HNO₃, HCl and HClO₄ media using cyanex-272 (bis[2,4,4 trimethyl pentyl] phosphinic acid)/n-dodecane has been carried out. In the case of HNO₃ and HClO₄ media, the distribution ratio (D) value first decreases and then increases, whereas from HCl medium it first decreases and then remains constant with increase in H⁺ ion concentration. At lower acidities, U(VI) was extracted as UO₂(HA₂)₂ by an ion exchange mechanism, whereas at higher acidities as UO₂(NO₃)₂ ^.2(H₂A₂) following a solvation mechanism. The D for U(VI) by cyanex-272, PC-88A and DEHPA at low acidities follows the order cyanex-272 > PC-88A > DEHPA. Also, cyanex-272 was found to extract U(VI) more efficiently than TBP at 2M HNO₃. The effect of diluents on the extraction of U(VI) by cyanex-272 followed the order cyclohexane > n-dodecane > CCl₄ > benzene. The loading of U(VI) into cyanex-272/n-dodecane from 2M HNO₃ has shown that at saturation point, cyanex-272 was 78% loaded. No third phase was observed at the saturation level. The stripping of U(VI) from the loaded organic phase was not possible with water, it was poor with acetic acid and sodium acetate but quantitative with oxalic acid, ammonium carbonate and sodium carbonate.     

Extraction of micro- and macroconcentrations of rare earth ions with the mixture of D2EHPA and TBP in n-hexane and cyclohexane

The synergistic solvent extraction of Eu(III) and some other rare earth elements from nitrate solutions (HNO₃+LiNO₃) by a mixture of (TBP+D2EHPA) in n-hexane and cyclohexane has been investigated at 22 °C. Antagonism found in europium extraction from 0.1M HNO₃ transforms into a synergistic effect. The synergistic effects existing for all investigated metals in extraction from 0.1M HNO₃+3M LiNO₃ were caused by formation of mixed complexes of the type Ln(D2EHPA)_2nH_2n–3+1(NO₃)₁TBP_m, where 1=1 or 2. The selectivity of the extraction in a synergistic system is lower for the La–Yb pair than in the case of D2EHPA extraction under the same conditions. On the other hand, the application of the synergistic mixture is more suitable for Eu–Ho separation. Thus the synergistic effect can be used for the separation or refining of some lanthanides.     

Solvent Extraction of Alkaline Earths with 1-Phenyl -3-Methyl 4 Stearoylpyrazol - 5 - One and Topo

Abstract

The synergic extraction of Ca, Sr, and Ba ions from aqueous solutions into cyclohexane or benzene containing 1- pheny 1 - 3 - methyl - 4 - stearoylpyrazol - 5 - one (HPMSP) and TOPO has been studied. Quantitative extraction (log D>2) was attained at pH>5.4 for Ca, pH>6.5 for Sr, and pH>7.3 for Ba when cyclohexane containing 0.05 M HPMSP and 0.01 M TOPO was used, and the corresoponding values for benzene were 6.5, 7.8, and 8.4. Extracted species were M(PMSP)₂(TOPO)₃ (M=Ca, Sr, Ba) for cyclohexane and Ca(PMSP)₂(TOPO)₃ and Sr (or Ba) (PMSP)₂(TOPO)₂ for benzene.