Sodium and potassium pervanadates

Russian Chemical Bulletin -     

Coordination polymers of copper(I) halides and neutral heterocyclic thiones with new coordination modes

Reaction of copper(I) chloride or bromide with equimolar amounts of the neutral pyrimidine-2-thione ligand (pymtH) afforded linear chain polymers [Cu(pymtH)X]n (X = Cl, Br) with the pymtH ligand acting as a bridging N, S donor. In contrast, copper(I) iodide under the same conditions gave the dimeric complex [Cu(pymtH)2I]2 with the pymtH ligand adopting monodentate coordination mode through the exocyclic sulfur atom in terminal and bridging modes. Reactions of the heterocyclic thione ligand 2,4,6-trimercaptotriazine (H3TMT) with copper(I) halides afforded novel three-dimensional polymers, which crystallized in the cubic space group Pa. Each copper(I) ion is coordinated by three S atoms of three distinct H3TMT ligands, and each H3TMT acts as a tridentate bridging ligand linking three copper(I) ions through its sulfur atoms, thus forming two independent three-dimensional (3D) networks. The network belongs to a three-connected (10, 3)-a topology, which is enantiometric and interpenetrating. In all complexes the ligands are present in the thione form, and all halides are terminally coordinated to copper(I) ions. The photoluminescent and thermal properties of the complexes have also been investigated.     

Transition-metal complexes of boron-new insights and novel coordination modes

Since the publication of the last review in 1998, the transition-metal chemistry of boron has continued to raise unceasing interest. Boryl complexes, representing the most extensive subclass, have remained a focus of intense research, particularly for their implication in the metal-mediated functionalization of organic substrates. Absolute novelties such as borane complexes and terminal borylene complexes have been structurally authenticated. Upon further elaboration of these compounds, the known coordination modes of boron-based ligands have grown considerably. Combined structural and theoretical investigations have contributed to elucidate the fundamental electronic characteristics of the transition-metal-boron bond and are leading to applications of these compounds. The most useful synthetic strategies for the generation of transition-metal-boron bonds are highlighted here, and the most recent and intriguing compounds that have been reported are outlined and discussed.     

Variation in coordination modes of aromatic N-oxides in lanthanum(III) coordination polymers

Two new coordination polymers of lanthanum(III) benzoate having pyridine N-oxide and 4,4′-bipyridyl-N,N′-dioxide as ancillary ligands are synthesized and characterized. Different binding modes of the N-oxide are demonstrated; pyridine N-oxide binds as a bridging ligand, whereas 4,4′-bipyridyl-N,N′-dioxide is monodentate.     

The Raman active internal vibrational modes of potassium nitrate

The Raman active internal vibrational modes of single crystal orthorhombic potassium nitrate have been studied in various polarizations. The full multiplet structure predicted by factor group analysis for the v₂ and v₃ regions has been observed for the first time. The expected site group splitting of the v₄ mode was not observed and can be assumed to be less than 0.5 cm^?1.     

New coordination modes at molybdenum for 2-diphenylphosphinoaniline derived ligands

The complexes [MoCl3(1-N,2-Ph2P-C6H4)2] (1) and {MoCl(Nt-Bu)[1-micro(N),2-(Ph2P)C6H4]}2 (2) have been obtained from the reaction of 2-diphenylphosphinoaniline [1,2(NH2)(Ph2P)C6H4] with either sodium molybdate [Na2MoO4] (in the presence of Et3N and Me3SiCl) or [MoCl2(Nt-Bu)2(DME)]; the crystal structure of 1 reveals a novel MoNC2PN six-membered conjugated ring system derived from a P-N coupling reaction between two ligands, whilst that of 2 reveals bridging imido/terminal phosphine ligation.     

Phase selection and discovery among five assembly modes in a coordination polymerization

The combination of zinc(II) nitrate with 1,3,5-(triscarboxyphenyl)benzene (H 3BTB) leads to five different microporous coordination polymers (MCPs). Two of these were previously known (MOF-177 and MOF-39), whereas polymer-induced heteronucleation was used in the discovery of three phases that have not been previously reported ( Zn/BTB ant, Zn/BTB tsx, and Zn/BTB dia). Modification of crystallization conditions allows for the bulk-scale synthesis of each of these MCPs. Zn/BTB ant and Zn/BTB tsx are each interpentrated 6,3-connected nets composed of the basic zinc carboxylate secondary building unit (SBU) and the tritopic linker BTB. The underlying noninterpenetrated net of Zn/BTB ant is derived for the net of anatase, whereas that of Zn/BTB tsx is the previously unreported "tsx" framework. Zn/BTB dia consists of an underlying diamondoid net in which four linear, trinuclear zinc hourglass SBUs are arranged about a central mu 4-oxo anion as the tetrahedral unit in the net and BTB further links the hourglass SBUs. Zn/BTB ant, Zn/BTB tsx, and MOF-177 are here defined as polymorphic frameworks in that each is composed of the same SBU and linker but differ in topology and thus pore structure. These frameworks may be called a polyreticular series by analogy to several reported isoreticular series. The effect of linker-linker interactions are discussed.     

PAs3S3 cage as a new building block in copper halide coordination polymers

First examples of the coordination chemistry of the PAs(3)S(3) cage were obtained from solutions of PAs(3)S(3)·W(CO)(5) (1) in CH(2)Cl(2) or CH(2)Cl(2)/toluene and CuX (X = Cl, Br, I) in MeCN through interdiffusion techniques. Crystals of [Cu(PAs(3)S(3))(4)]X (2, X = Cl; 3, X = Br) and [(Cu(2)I)(PAs(3)S(3))(3)]I (4) were obtained and characterized by Raman spectroscopy (2) and single-crystal X-ray crystallography. The solid-state structures reveal an unexpected coordination versatility of the PAs(3)S(3) ligand: apical phosphorus and bridging sulfur atoms interact with copper, while As···X interactions determine the dimensionality of the frameworks. The structures of 2 and 3 contain tetrahedral [(PAs(3)S(3))(4)Cu](+) cations as secondary building units (SBUs), which are arranged by interactions with Cl(-) or Br(-) anions into two- and three-dimensional substructures. These interpenetrate into a (2D + 3D) polycatenane. Compound 4 is built up by a one-dimensional [(Cu(2)I)(PAs(3)S(3))(3)](n)(n+) ribbon with PAs(3)S(3) cages as P,S-linkers. The As atoms of the exo PAs(3)S(4) linkers interact with iodide counterions (3.35 < d(As-I) < 3.59 ?). The resulting two-dimensional layer is organized by weak As···I interactions (d(As-I = 3.87 ?) into a 3D network.     

A calcium(II) coordination polymer showing two different bridging 2-carbamoyl-4-nitrobenzoate coordination modes

Aqueous reaction of CaCO₃ with 2-carbamoyl-4-nitrobenzoic acid (2-ca-4nbaH) results in the formation of a 1-D coordination polymer [Ca(H₂O)₂(2-ca-4nba)₂] (1), which crystallizes in the centrosymmetric triclinic space group P 1. The structure consists of a central Ca(II), two coordinated waters, a symmetrical bridging (µ₂-η ¹ : η ¹) 2-ca-4nba, and a tridentate bridging (µ₂-η ² : η ¹) 2-ca-4nba. The calcium in 1 is coordinated by two water molecules and five oxygens of four symmetry-related 2-ca-4nba, resulting in a distorted pentagonal bipyramidal {CaO₇} polyhedron. Pairs of {Ca(H₂O)₂} units are linked into a 1-D coordination polymer extending along the a-axis with the aid of pairs of bridging 2-ca-4nba ligands. In the infinite chain, alternating pairs of Ca(II) ions exhibit Ca ··· Ca separations of 4.124 and 4.855 Å.     

Different coordination modes and supramolecular aggregations in copper(II) pentane-2,4-dionato compounds with 2-pyridone and 3-hydroxypyridine

Abstract  

Copper(II) bis(pentane-2,4-dionato-κ² O,O′) compounds with 2-pyridone (1) and 3-hydroxypyridine (2) were prepared by the reaction of bis(pentane-2,4-dionato-κ² O,O′)copper(II) with selected ligands. The coordination of Cu(II) in both compounds is square pyramidal with the fifth coordination site occupied by the carbonyl oxygen atom of the 2-pyridone ligand in 1 and by the nitrogen atom of 3-hydroxypyridine in 2. The X-ray crystallographic studies revealed different crystal aggregation influenced by the ability of the 2-pyridone ligand to act as a hydrogen bond donor and acceptor, and 3-hydroxypyridine acting only as a hydrogen bond donor. Intermolecular N–H···O hydrogen bonding forms dimers in 1 and infinite chains in 2. Three-dimensional aggregation is achieved by π–π interactions and C–H···π (arene) hydrogen bonding.     

One- and two-dimensional coordination networks of the tetracyanoethylene anion-radicals with potassium counter-ions

Potassium-mirror reduction of tetracyanoethylene (TCNE) acceptor in tetrahydrofuran affords K(THF)₂ TCNE salt (1) showing double TCNE/K chains assembled via unusual μ₃-TCNE-bridging of potassium cations. These parallel ladder-type chains are further tethered by pairs of THF bridges between potassium centers and by intermolecular π-bonding in (TCNE)₂^2? dimers, and this results in formation of quasi-2-D coordination networks. In the presence of crown-ether ligand, the same potassium-mirror reduction lead to formation of [K(18-crown-6)(THF)₂]TCNE salt (2) in which monomeric tetracyanoethylene anion-radicals are positioned between bulky [K⁺(18-crown-6)(THF)₂] counter-ions. In comparison, crystallization of tetracyanoethylene anion-radicals with K⁺(18-crown-6) counter-ions in dichloromethane affords K(18-crown-6)TCNE salt (3) consisting of 1-D chains with 1,2-(N,N’)-TCNE bindings of potassium cations (nested in the crown-ether cavities). Temperature-dependent magnetic susceptibility study revealed essentially isolated tetracyanoethylene anion-radicals (S = 1/2) in this 1-D coordination polymer.     

Five coordination modes of 4-aminopyrimidine with N-hydroxy-ethylethylenediaminetriacetatoruthenate(II)

Summary The complex [Ru^II(hedta)(4NH₂pym)]⁻, hedta³⁻ = N-hydroxyethylethylenediaminetriacetate, 4NH₂pym = 4-aminopyrimidine, exists at pH 7 as five different coordination isomers, which are most readily distinguished by their electrochemical waves in comparison with the 2-aminopyridine (2NH₂py) complex. The 2NH₂py complex exhibits N(1) (pyridine bound), exo-NH₂ (amine bound) and N(1), NH₂-chelated species. The 4NH₂pym complex forms N(1), exo-amine and N(3), NH₂-chelated isomers analogues to the 2NH₂py species, but also engages in η² (olefin bound) coordination of the dearomatized 4NH₂pym ring in C(5)–C(6), and another η² type of complex involving electron density between N(1) and N(3) of the ring (η³ form). N(1), η² and η³ isomers have also been detected for unsubstituted pyrimidine (pym), 4-methylprimidine (4CH₃pym) and 2-aminopyrimidine (2NH₂pym). Electrochemical waves (V versus NHE) for the five isomers are assigned as follows: (Ru^II/III) exo-NH₂ (0.06 V), N(1) (0.29 V), η² (0.49 V); (Ru^II/III) η³ (0.76 V); N(3), NH₂-chelated (1.09 V).     

New series of indium formates: hydrothermal synthesis, structure and coordination modes

Three new indium(III) compounds, In(HCOO)3 (1), In2(HCOO)5(OH) (2), and In(HCOO)2(OH) (3), were synthesized under hydrothermal conditions and characterized by single crystal and powder X-ray diffraction experiments, as well as by IR spectroscopy, elemental analysis, and coupled TG-DSC-MS measurement. All of these compounds adopt 3D framework structures consisting of InO6 octahedra and the 2.11 binding modes of formate with the (syn, syn-; syn, anti-; anti, anti-) configurations. The structural investigation of these indium formates reveals that the gradual introduction of the hydroxyl groups into the structures induces the polymerization of the InO6 octahedra, that is, InO6 is isolated in 1, becomes dimeric in 2, and finally forms 1D chains in 3. In addition, a simple formula that may be used for estimating the overall coordination number of the formate in Ma(HCOO)bLc is proposed.     

Polynuclear palladium complexes with 3,5-dimethylpyrazolate exhibiting three different coordination modes

The characterisation of dinuclear pyrazolato-bridged Pd(II) complexes, [(Pd(mu-dmpz)Cl(Hdmpz))2] (1) and [(Pd(mu-dmpz)(dmpz)(Hdmpz))2] (2) (Hdmpz=dimethylpyrazole), has been carried out. An X-ray study of compound 2 reveals the existence of intramolecular N-H...N hydrogen bonds between neighbouring dmpz groups. Compound 2 has been deprotonated and both acidic hydrogen atoms substituted by two metal atoms of Cu(I), Ag(I) or Au(I) to give the tetranuclear compounds [Pd2M2(mu(2)-dmpz-kappaN,N')6] (M=Cu, Ag, Au). The structure of these compounds resembles a box with a small cavity inside. There are also three pi-electron-rich clefts between each of the three pairs of azolato rings, capable of further complexation. The reactions of [Pd2M2(mu(2)-dmpz-kappaN,N')6] (M=Cu, Ag, Au) with AgClO4 render compounds of the type [(Pd2M2(mu(2)-dmpz-kappaN,N')2(-)(mu(3)-dmpz-kappaN,N',C4)4Ag2(mu(2)-O2ClO2))2] (M=Cu, Ag, Au). The X-ray structures of crystals obtained from a solution of compounds [(Pd2M2(mu(2)-dmpz-kappaN,N')2(mu(3)-dmpz-kappaN,N',C4)4Ag2(mu(2)-O(2)ClO2))2] (M=Ag, Au) in acetone reveals a [(Pd2M2(mu(2)-dmpz-kappaN,N')2(mu(3)-dmpz-kappaN,N',C4)4Ag(OCMe2)(OClO3)Ag(mu(2)-O2ClO2))2] stoichiometry, indicating that only two of the three pi-electron-rich clefts have been used to accommodate Ag+ ions. Each of the silver atoms are located in between two 3,5-dmpz rings and are eta(1)-bonded to the C4 atom of each group.     

Photostereochemistry and photoaquation reactions of [Cr(tn)3]3+: theoretical studies show the importance of reduced coordination conical intersection geometries

We have performed TD-DFT and CASSCF calculations to understand the spectroscopy and reactive photochemistry of the [Cr(tn)(3)](3+) complex. Our results show that, after population of a quartet ligand field excited state, the system relaxes by dissociation of a Cr-N bond to reach a quasi-trigonal bipyramid five-coordinate species that is a conical intersection connecting the excited and ground quartet manifolds. Nonadiabatic relaxation through these leads to square pyramidal structures that can coordinate water and account for the observed monoaquated photoproducts. Such features are also present on the potential energy surfaces of these photoproducts and account for the range of experimentally observed photostereoisomers of the photoaquation reactions.     

Synthesis,structure, and properties of a new 3D hydrogen-bonded porous coordination polymer

A new coordination polymer, [Cd(HMal)(Bipy)(H₂O) · 2H₂O (I) (H₃Mal is malic acid, Bipy is 4,4′-bipyridine), has been synthesized from H₃Mal and Bipy under hydrothermal conditions and characterized by elemental analysis, IR, TG, and single-crystal X-ray diffraction. The X-ray diffraction analysis reveals that I (C₁₄H₁₆N₂O₇Cd) crystallizes in the orthorhombic system, space group Ibam. The adjacent cadmium(II) atoms were first interconnected by the HMal ligands via carboxylate oxygen atoms and its adjacent hydroxyl group to generate an infinite zigzag [Cd(HMal)] _n chain, which are further linked by Bipy ligands to form a 2D wavelike layer. Interestingly, the adjacent layers are further connected via hydrogen bonds, giving rise to a 3D porous framework with a cross-sectional area of 11.690 × 9.326 Ų. The unit cell parameters for I: a = 8,457(1), b = 22.030(7), c = 23.066(7) V = 4297(2) ų, Z = 4.