Synthesis of New Crystalline Pu(V) Compounds from Solutions: V. Crystal Structure of [Co(NH3)6][PuO2(C2O4)2] · 3H2O

The compound [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O was studied by single crystal X-ray diffraction. The structure contains dimeric complex anions [PuO₂(C₂O₄)₂] ₂ ⁶⁻ in which the coordination polyhedra of the Pu atoms are distorted pentagonal bipyramids sharing a common equatorial edge. In going from [Co(NH₃)₆] · [NpO₂(C₂O₄)₂] · 3H₂O to [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O, the An-O distances, both axial (in the actinyl group) and equatorial, decrease virtually isotropically. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 419–422. Original Russian Text Copyright ? 2005 by Grigor'ev, Antipin, Krot, Bessonov.     

Synthesis and characterisation of infinite coordination networks with 1,6-bis(4-pyridyl)hexane and copper nitrate

Crystallisation of 1,6-bis(4-pyridyl)hexane (Py₂C₆H₁₂) with copper nitrate gives two different phases. Phase 1 of composition [Cu(Py₂C₆H₁₂)₃(NO₃)₂]·2[Cu(Py₂C₆H₁₂)₂(H₂O)(NO₃)]·2(NO₃)·EtOH consists of two different infinite chains in a 1:2 ratio that are interlocked. Hydrogen bonds link chains I to II and chains II to II. In contrast phase 2 of composition [Cu₂(Py₂C₆H₁₂)₄(H₂O)₂]·(NO₃)₄·(Py₂C₆H₁₂)·(EtOH)·2(H₂O) is based upon an infinite 3D framework. It consists of four interpenetrating 3D networks that are crystallographically equivalent.     

Crystal Structure of Double Co(NH3)6 3 + Np(V) Malonates Co(NH3)6(NpO2C3H2O4)2A·H2O (A = OH and NO3)

X-ray diffraction analysis of Co(NH₃)₆(NpO₂C₃H₂O₄)₂NO₃·H₂O (I) and Co(NH₃)₆(NpO₂· C₃H₂O₄)₂OH·H₂O (II) showed that they consist of [NpO₂C₃H₂O₄] _n ^{n -} infinite anionic chains, [Co(NH₃)₆]^{3 +} cations, NO₃ ^- (I) and OH^- (II) anions, and molecules of crystallization water. The anionic chain structure is similar to that in the known compound Co(NH₃)₆(NpO₂C₃H₂O₄)₂C₃H₃O₄. Neptunium(V) atoms occur in hexagonal-bipyramidal environment. The coordination capacity of malonate anions is 6, and they simultaneously coordinate three neptunyl(V) cations NpO₂ ⁺ in the chain.     

Crystallization of salts M3[NpO4(OH)2]·nH2O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures. Synthesis and structure of a new Np(VII) compound, Na3[NpO4(OH)2]·6H2O

Precipitation of salts M₃[NpO₄(OH)₂]·nH₂O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures (about ?10°C) was studied. From solutions with [OH^?] > 9.5 M, these compounds are isolated as coarse black crystals in high yield without impurity of other phases. The K, Rb, and Cs salts crystallize in the form of the previously studied compounds K₃[NpO₄(OH)₂]·2H₂O and M₃[NpO₄(OH)₂]·3H₂O (M = Rb, Cs). In the case of Na, a new hydrate Na₃[NpO₄(OH)₂]·6H₂O was obtained, and its crystal structure was determined. Crystals of the hexahydrate consist of centrosymmetrical tetragonal-bipyramidal anions [NpO₄(OH)₂]^3?, crystallographically independent Na(1) and Na(2) cations, and water molecules. The coordination surrounding of the Np atom is characterized by noticeable difference (Δ = 0.0203 Å) in the Np-O bond lengths in the equatorial plane of the bipyramid. The [NpO₄(OH)₂]^3? anions are combined with the Na(2) cations to form infinite chains [Na(2)NpO₄(OH)₂(H₂O)₂]^2? in such a manner that the lateral edges of the anion are simultaneously the lateral edges of the Na(2) coordination polyhedron. Incorporation of one of the two crystallographically independent O atoms of the NpO₄ group into the Na(2) coordination surrounding is responsible for a noticeable difference in the Np-O bond lengths in the equator of the [NpO₄(OH)₂]^3? anion. The types of hydrogen bonding in the structures of Na3[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4, 6) are compared.     

Interaction of methanesulfonic acid with actinide ions. The new complexes HImid[Np(C2O4)(CH3SO3)3(H2O)2], [NpO2(Terpy)(CH3SO3)(H2O)]·2H2O, and [UO2(CH3SO3)2(H2O)]

Complexation of methanesulfonic acid with Np(IV), Np(V), and U(VI) ions in aqueous solutions was studied. New crystalline compounds HImid[Np(C₂O₄)(CH₃SO₃)₃(H₂O)₂] (I), [NpO₂(Terpy)(CH₃SO₃)·(H₂O)]·2H₂O (II), and [UO₂(CH₃SO₃)₂(H₂O)] (III) were isolated. The absorption spectra of all the compounds in the IR, visible, and UV ranges were examined. The relationship between the composition, crystal structure, and IR and electronic absorption spectra of the complexes is discussed. Original Russian Text ? G.B. Andreev, N.A. Budantseva, I.G. Tananaev, B.F. Myasoedov, 2009, published in Radiokhimiya, 2009, vol. 51, no. 3, pp. 197–201.     

Synthesis of co-ordination networks from flexible bis-(4-pyridyl) ligands and cadmium salts.

Crystallisation of flexible dipyridyl ligands with Cd(NO₃)₂·4H₂O, Cd(ClO₄)₂·xH₂O or Cd(NO₃)₂·4H₂O and KSCN gives co-ordination networks of composition [Cd(ClO₄)₂(Py₂C₃H₆)₂(H₂O)₂]·Py₂C₃H₆ 1 (Py₂C₃H₆ =1,3-bis(4-pyridyl)propane); [Cd(ClO₄)₂(Py₂C₂H₄)₃] 2 (Py₂C₂H₄ =1,2-bis(4-pyridyl)ethane); [Cd(NCS)₂(Py₂C₃H₆)] 3; [Cd₂(NO₃)₄(o-C₆H₄(CH₂CH₂4-Py)₂)₄] 4 (o-C₆H₄(CH₂CH₂Py)₂ =1,2-bis[2-(4-pyridyl)ethyl] benzene and [Cd(NO₃)₂(PyCH₂CH₂CH=CHCH₂CH₂Py)₃] 5 (PyCH₂CH₂CH=CHCH₂CH₂Py =1,6-bis(4-pyridyl)hex-3-ene). The compounds were characterised by X-ray single crystal diffraction studies which revealed the presence of different polymeric motifs. Structures 1 and 5 consist of 1-D polymeric chains, structure 4 consists of a 2-D polymeric network and structure 3 is a 3-D polymeric network. None of these exhibit lattice interpenetration. However structure 2 consists of three identical but independent interpenetrating 3-D lattice networks.     

New data on sodium salts of Np(VII) and Pu(VII)

A new Pu(VII) compound, Na₃[PuO₄(OH)₂]·2H₂O, was prepared by X-ray diffraction analysis, and its structure was studied. To reveal the character of actinide contraction in going from Np(VII) to Pu(VII), the geometric parameters of the tetragonal-bipyramidal surrounding of Pu(VII) in the [PuO₄(OH)₂]³⁻ anion were compared with those of Np(VII) in the previously studied isostructural compound Na₃[NpO₄(OH)₂]·2H₂O. To reveal the specific feature of hydrogen bonding in crystals of the general composition Na₃[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4), the structure of the compound Na₃[NpO₄(OH)₂]·4H₂O studied previously by the photographic method was refined. The effect of hydrogen bonds on the geometric characteristics of the coordination polyhedra of the Np and Na atoms was considered.     

Synthesis and X-ray diffraction study of monohydrates of rubidium and cesium salts of Np(VII) and Pu(VII)

The compounds Rb₃[AnO₄(OH)₂]·H₂O and Cs₃[AnO₄(OH)₂]·H₂O, where An = Np or Pu, were prepared as single crystals by crystallization from alkaline solutions of Np(VII) and Pu(VII) in the course of their drying at 70–75°C. The crystals were subjected to X-ray diffraction analysis. All the compounds are isostructural and contain An atoms in the form of [AnO₄(OH)₂]^3? anions in which the oxygen surrounding of the An atoms is a slightly distorted tetragonal bipyramid. The averaged An-O distances in the equatorial planes of the bipyramids vary insignificantly (within 1.884–1.892 Å), tending to slightly decrease in going from Np to Pu. This trend is more pronounced for averaged An-OH distances, which vary in the range 2.328–2.368 Å. That is, as in the case of the other previously studied An(VII) compounds, the actinide contraction is mainly manifested in shortening of the An-OH distances. One of the features of Rb₃[AnO₄(OH)₂]·H₂O and Cs₃[AnO₄(OH)₂]·H₂O structures, as compared with the trihydrates, is the lack of the symmetry center in [AnO₄(OH)₂]^3? anions.     

Crystal Structure of a Double Oxalate of Np(V) and Co(NH3)

The crystal structure of a dioxalate complex Co(NH₃)₆NpO₂(C₂O₄)₂·1.5H₂O was studied. The structure consists of centrosymmetrical dimeric anions [NpO₂(C₂O₄)₂] ₂ ⁶⁻ , [Co(NH₃)₆]³⁺ cations, and water molecules of crystallization. The NpO ₂ ⁺ dioxocations have close Np-O bond lengths (average 1.824 Å) and are noticeably bent (ONpO angle 175.6°). Each dioxocation in the [NpO₂(C₂O₄)₂] ₂ ⁶⁻ anion is surrounded by five oxygen atoms of three C₂O ₄ ²⁻ anions; the Np coordination polyhedra are pentagonal bipyramids sharing a common edge. __________ Translated from Radiokhimiya, Vol. 47, No. 6, 2005, pp. 495–499. Original Russian Text Copyright ? 2005 by Charushnikova, Krot, Polyakova.     

Synthesis and structure of actinide(VII) compounds Rb3NpO4(OH)2·3H2O and Rb3PuO4(OH)2·3H2O

Actinide(VII) salts Rb₃[NpO₄(OH)₂]·3H₂O (I) and Rb₃[PuO₄(OH)₂]·3H₂O (II) were prepared as single crystals and examined by X-ray diffraction. The compounds are isostructural and crystallize in the monoclinic system, space group C2/c, Z = 4; unit cell parameters: a = 12.1544(3), b = 10.9942(2), c = 7.789(2) ?, ?? = 91.0930(11)° for I and a = 12.1254(3), b = 10.9506(2), c = 7.7699(2) ?, ?? = 90.8253(12)° for II. The main structural elements of I and II are centrosymmetrical anions [AnO₄(OH)₂]^3? forming together with water molecules, owing to strong hydrogen bonding, chains oriented along [101]. In [AnO₄(OH)₂]^3? anions, the central An(VII) atom has a tetragonal-bipyramidal oxygen surrounding. The An-O(OH) interatomic distances decrease in going from I to II owing to actinide contraction by a factor of ??2 more strongly than the An-O bond lengths in the equatorial planes of the bipyramids. The previously studied structure of Cs₃[NpO₄(OH)₂]·3H₂O (III) was refined.     

Synthesis and study of Np(V) sesquioxalates

Neptunium(V) at its relatively high concentrations in oxalate solutions forms, along with the mono-and bioxalate complexes, the intermediate binuclear anion (NpO₂)₂(C₂O₄) ₃ ^4? . This anion gradually crystallizes from cold aqueous-ethanol solutions in the form of the compound Na₄(NpO₂)₂(C₂O₄)₃ · 6H₂O, and from hot aqueous-ethanol solutions, in the form of a lower hydrate, Na₄(NpO₂)₂(C₂O₄)₃ · 2H₂O. Both compounds were characterized by powder X-ray diffraction and by electronic absorption and IR spectra. The thermal behavior of the hexahydrate in air was studied. Attempts to prepare the related crystalline compounds M₄(NpO₂)₂(C₂O₄)₃ · nH₂O with M = Li or NH₄ failed.     

Layered double hydroxides intercalated with EDTA as effective sorbents for U(VI) recovery from wastewater

The performance of the synthetic hydrotalcite-like sorbents, initial {[Zn₄Al₂(OH)₁₂]CO₃·nH₂O} and heat-treated (Zn₄Al₂O₇) forms and the form intercalated with EDTA and prepared in a nitrogen atmosphere from [Zn₄Al₂(OH)₁₂]Cl₂·nH₂O, was evaluated and compared. Increased concentrations of hydrocarbonate and carbonate ions do not noticeably affect the degree of U(VI) recovery from wastewaters with pH 8, which is due to tight binding of U(VI) with EDTA anions in the interlayer space of layered double hydroxides. [Zn₄Al₂(OH)₁₂]EDTA·nH₂O is one of the most effective and cheapest synthetic sorbents for recovering from aqueous media not only cationic but also anionic U(VI) species, which is particularly important. Therefore, the sorbent can be recommended for practical use.     

Synthesis and crystal structure of double Ln(III) malonates with Co(NH3) 6 3+ in the outer sphere

Double Ln(III) malonates of two different compositions crystallize from malonate solutions containing [Co(NH₃)₆]³⁺ ions. Lanthanides of the beginning of the series form compounds of the composition [Co(NH₃)₆][Ln(mal)₂]₃·6H₂O (I) (Ln = La, Ce, Pr, Nd; mal = C₃H₂O^2?), and those of the end of the series form compounds of the composition [Co(NH₃)₆]₂[Ln₃(mal)₇(Hmal)(H₂O)₄]·nH₂O (II) (Ln = Tb, Ho, Er, Tm). Structure I is based on trimeric anionic complexes [Ln₃(mal)₆]^3? linked with each other to form a branched 3D network with [Co(NH₃)₆]³⁺ cations and water molecules accommodated in large voids. The coordination mode of malonate ions in I with the coordination capacity equal to 5 was unknown previously for lanthanide malonate compounds. The Ln(1) atom has the maximum possible for malonate compounds coordination number (CN) 12, and the Ln(2) atom has CN 9. The structure of II consists of anionic chains [Ln₃(mal)₇(Hmal)(H₂O)₄] _n ^3? between which the [Co(NH₃)6]₃₊ cations and water molecules are arranged. One independent malonate ion in the structure is coordinated in the bidentate chelate fashion to the Ln(1) atom, and the other independent chelate-bridging ligand is coordinated in the bidentate fashion to the Ln(2) atom and in the monodentate fashion to the Ln(1) atom. As a result, tetrameric fragments linked in anionic chains are formed in the structure of II. The Ln(1) and Ln(2) atoms have CN 8.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: II. Double Pu(V) Oxalates with Co(NH<Subscript>3</Subscript>)<Subscript>6</Subscript><Superscript>3+</Superscript> Ions in the Outer Sphere

Crystalline compounds of the general composition Co(NH³)⁶PuO₂(C₂O₄)²·nH₂O (n = 2, 3, 5) were isolated from freshly prepared neutral oxalate solutions of Pu(V) by addition of Co(NH₃)₆³⁺ ions. These compounds are fairly stable in storage in air and poorly soluble in water. Previously unknown double Np(V) oxalates Co(NH₃)₆NpO₂(C₂O₄)·nH₂O (n = 2, 5) were also synthesized and studied. All the compounds of Pu(V) and Np(V) of the same composition are mutually isostructural. The behavior of these compounds at heating was studied, and their IR spectra were measured. The optical spectra of new Np(V) compounds were measured.     

Synthesis,electronic state,and particle size stabilization of nanoparticulate [Co(OH)<Subscript>2</Subscript>(H<Subscript>3</Subscript>O)<Stack><Subscript>δ</Subscript><Superscript>+</Superscript></Stack>]<Superscript>δ+</Superscript>

We have synthesized nanoparticulate cobalt(II) hydroxide containing Co²⁺ in tetrahedral oxygen coordination (Co _Td ²⁺ ), atypical of such systems: nano- [Co(OH)₂(H₃O) _δ ⁺ ]^δ+. The (Co _Td ²⁺ ) coordination in the hydroxide is inferred from its electronic diffuse reflectance spectrum, which shows a multiplet of strong absorption bands at 14500, 15000, and 16000 cm^?1 (⁴ A ₂(F)-⁴ T ₁(P) transition). Nanoparticulate cobalt(II) hydroxide forms in a weakly acidic medium under essentially nonequilibrium conditions due to supersaturation (by three to four orders of magnitude) with the starting reagents (CoCl₂ and LiOH) at the instant of the formation of the poorly soluble phase Co(OH)₂. Presumably, colloidal particles of nanoparticulate cobalt(II) hydroxide in a weakly acidic aqueous medium have a positive surface charge, compensated by a counter-ion (Cl^?) layer: nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ · δCl^?. The XRD patterns of pastes (gels) containing this hydroxide show three broad-ened lines with d = 5.31 (2θ = 16.7°), 2.77 (2θ = 32.3°), and 2.32 Å (2θ = 38.8°). According to small-angle X-ray scattering data, nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ has a narrow particle size distribution (1.0–2.0 nm). Synthesis and storage conditions are identified which ensure stabilization of the electronic state and particle size of nano-[Co(OH)₂(H₃O) _δ ⁺ ]^δ+ for a long time.     

Synthesis and structural features of Np(VI) and Pu(VI) isophthalates

New An(VI) isophthalate complexes [PuO₂(C₈H₄O₄)] (I), Cs₂[(NpO₂)₂(C₈H₄O₄)₃]·4H₂O (II), [H₃O]₂[(NpO₂)₂(C₈H₄O₄)₃]·nH₂O (III), and [H₃O][NpO₂(C₈H₄O₄)(C₈H₅O₄)]·2H₂O (IV) with the An(VI): Lig ratios of 1: 1 (I), 1: 1.5 (II, III), and 1: 2 (IV) were synthesized and studied by single crystal X-ray diffraction. In complex I, the coordination polyhedron of the Pu(1) atom is a pentagonal bipyramid whose equatorial plane is formed by the oxygen atoms of four [C₈H₄O₄]^2– anions. The coordination capacity of the ligand in complex I is maximal among compounds I–IV and equal to 5, with each [C₈H₄O₄]^2– anion binding four PuO₂²⁺ cations into electrically neutral layers. In the structures of II and III, the coordination polyhedra of the Np(1) atoms are hexagonal bipyramids whose equatorial planes are formed by the oxygen atoms of three [C₈H₄O₄]^2– anions. Two crystallographically independent [C₈H₄O₄]^2– anions exhibit the coordination capacity equal to 4, each binding two NpO₂²⁺ cations in the chelate fashion. As a result, doubled anionic layers are formed in the crystals of II and III. Outer-sphere cations influence the packing of doubled layers in the crystals: Complex II crystallizes in the monoclinic system, and complex III, in the orthorhombic system. In the structure of IV, the coordination polyhedron of the Np(1) atom is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of two [C₈H₄O₄]^2– anions and one [C₈H₅O₄]^– anion. The crystallographically independent bridging anion [C₈H₄O₄]^2– exhibits the coordination capacity equal to 4 and binds in the chelate fashion two NpO₂²⁺ cations to form chains, and the independent hydrogen isophthalate anion [C₈H₅O₄]^– binds one neptunyl(VI) cation in the chain in the chelate fashion, exhibiting the coordination capacity equal to 2.     

Synthesis and structure of crystalline complexes of Np(V) with 1,10-phenanthroline-2,9-dicarboxylic acid. Complexation in solution and spectral studies

Complexes of Np(V) with 1,10-phenanthroline-2,9-dicarboxylic acid, C₁₂H₆N₂(COOH)₂ (H₂PDA), of the compositions [(NpO₂)₂(PDA)(H₂O)₃]·H₂O (I), (NH₄)₂[NpO₂(PDA)]₂·3H₂O (II), and [C(NH₂)₃]₂[NpO₂·(PDA)]₂·4H₂O (III) were synthesized. The Np atoms in the crystal lattices of all the compounds have the pentagonal bipyramidal coordination surrounding, with the [C₁₂H₆N₂(COO)₂]^2? anions acting as chelate-bridging N,O-donor ligands. In the structure of I, two crystallographically independent NpO ₂ ⁺ dioxocations participate in the cation-cation interaction leading to the formation of tetrameric cation-cation complexes. The nonequivalence of the Np atoms is manifested in splitting of the main absorption band of Np(V) in the electronic spectrum of solid compound I. The structures of II and III are based on dimeric anionic complexes [NpO₂(C₁₂H₆N₂(COO)₂)] ₂ ^2? . Only one kind of complexes, NpO₂(PDA)^?, was detected in the solution, and high value of the concentration stability constant β, ～10¹² L mol^?1, is due to tetradentate coordination of the ligand.     

Synthesis,crystal structure,and spectral properties of a complex of U(VI) with <Emphasis Type="Italic">m</Emphasis>-hydroxybenzoic acid

A new complex compound of U(VI) with m-hydroxybenzoic acid, K[(UO₂)(C₇H₅O₃)₃]·5H₂O, was prepared and characterized. A single crystal X-ray diffraction study showed that the coordination polyhedron of the U atom is a hexagonal bipyramid whose equatorial plane is formed by the O atoms of carboxy groups of three anions of m-hydroxybenzoic acid. The K atoms act as outer-sphere cations linking the adjacent anions [UO₂(C₇H₅O₃)₃]⁻ into neutral dimers {[UO₂(C₇H₅O₃)₃]K(H₂O)₃}₂. The structure also contains water molecules of crystallization, retained by hydrogen bonds.     

Preparation of new zirconium phosphates by solvothermal reaction

Two types of new zirconium phosphates, [enH₂]Zr(OH)(PO₄)(HPO₄) (en; ethylene diamine) and (NH₄)₅[Zr₃(OH)₉(PO₄)₂(HPO₄)] were prepared under solvothermal condition using diethylene glycol as a solvent and their crystal structures were determined by using single crystal X-ray diffraction data. The former compound has the layer structure similar to that of γ-Zr(PO₄)(H₂PO₄) · 2H₂O, and protonated ethylene diamines were located in the interlayer space. At elevated temperatures, this compound decomposed by releasing protonated ethylene diamines and finally changed to ZrP₂O₇. The interlayer space was soft-chemically inactive unlike α-Zr(HPO₄)₂ · H₂O and γ-Zr(PO₄)(H₂PO₄) · 2H₂O. The later compound has the tunnel structure built up by corner-sharing ZrO₆ octahedra and PO₄ tetrahedra, and NH₄ ⁺ ion was located in the tunnel.