Solvent effects on the dimensionality of oxamato-bridged manganese(II) compounds

Abstract

Two new oxamate-containing manganese(II) complexes, [{Mn(H₂edpba)(H₂O)₂}₂]_n (1) and [Mn(H₂edpba)(dmso)₂]?dmso?CH₃COCH₃?H₂O (2) (H₄edpba = N,N′-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of 1 and 2 were characterized by single crystal X-ray diffraction. The structure of 1 consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H₂edpba^2? ligand and two carboxylate–oxygens from two other H₂edpba^2? ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an anti-syn conformation. A dmso solution of single crystals of 1 was placed under acetone atmosphere affording 2, whereas putting 2 in equimolar water:ethanol mixture results in 1. The molecular structure of 2 is made up of mononuclear manganese(II) units which are interlinked by weak C–H?π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic b axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through anti-syn carboxylate bridges for 1 [J = ?1.18 cm^?1, the Hamiltonian being defined as H = ?J S₁^.S₂] and very weak intrachain ferromagnetic interactions in 2 [J = + 0.046 cm^?1, H = ?J ∑_iS_i^.S_i + 1].     

Aluminum complexes with mono-and dianionic diimine ligands

The metathesis reaction of the magnesium complex [(dpp-BIAN)²⁻Mg²⁺(THF)₃] (dpp-BIAN is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with one equivalent of AlCl₃ in toluene gave the [(dpp-BIAN)²⁻AlCl₂]⁻[Mg₂Cl₃(THF)₆]⁺ complex (1). Reduction of dpp-BIAN with aluminum metal in the presence of AlCl₃ and AlI₃ in toluene and diethyl ether afforded the radical-anionic complex [(dpp-BIAN)⁻AlCl²] (2) and the dianionic complexes [(dpp-BIAN)²⁻AlI(Et₂O)] (3) and [(dpp-BIAN)²⁻AlCl(Et₂O)] (4), respectively. Compounds 1–4 were isolated in the crystalline state and characterized by IR spectroscopy and elemental analysis. The structures of compounds 1–3 were established by X-ray diffraction. Compound 2 was characterized by ESR spectroscopy. Compounds 3 and 4 were studied by 1H and 13C NMR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–415, March, 2006.     

Strained Structure in Ho0.5Sr0.5MnO3

The Ho_0.5Sr_0.5MnO₃ perovskite, synthesized in air, has been studied by combining neutron powder and electron diffraction techniques. The Pnma-type structure exhibits a strong tilting of the MnO₆ octahedra. This octahedra tilting and microtwinning involve a complex strained structure. No structural transition is observed down to 1.4 K, but short-range A-type antiferromagnetism running over only a few perovskite subcells is evidenced below ≈90 K. The different behavior of this perovskite compared to other Ln_0.5Sr_0.5MnO₃ perovskites is discussed in terms of A-site cationic mismatch.     

Interaction of bis(trimethylsilyl)acetylene complex of titanocene with mercury trifluoroacetate

The reaction of the bis(trimethylsilyl)acetylene complex of titanocene Cp₂Ti(Me₃SiC₂SiMe₃) with mercury trifluoroacetate (NF₃COO)₂Hg at 20 °C in a THF medium affords titanocene bis(trifluoroacetate) Cp₂Ti(OCOCF₃)₂ and metallic mercury. The structure of Cp₂Ti(OCOCF₃)₂ was established by the analytical and spectroscopic methods and X-ray diffraction analysis.     

Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Synthesis conditions, crystal structures, and magnetic properties of quasi-one-dimensional complex oxides Ca₃CuMnO₆ (space group P-1, z=4, triclinic cell) and Ca₃Co_1+xMn_1−xO₆ with x=0, 0.25, 1.0 (structural type K₄CdCl₆, space group R-3c, z=6) are presented. The crystal structures of Ca₃CoMnO₆ and Ca₃CuMnO₆ were refined using neutron and combined X-ray and neutron diffraction analysis, respectively. The interatomic distances in oxygen polyhedra were found. In contrast to ferromagnetic Ca₃Co₂O₆ (T_c=24 K), manganese-containing phases Ca₃Co_1+xMn_1−xO₆ are characterized by antiferromagnetic interactions with Neel temperatures 18 K (x=0.25) and 13 K (x=0). For Ca₃CuMnO₆T_N was established to be 6 K.     

Liquid Nickel Salts: Synthesis,Crystal Structure Determination,and Electrochemical Synthesis of Nickel Nanoparticles

New nickel‐containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so‐called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N‐alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf₂N^?), trifluoromethanesulfonate (OTf^?) and methanesulfonate (OMs^?). Several different N‐alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd‐even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements.     

Novel crystal modification of <Emphasis Type="Italic">fac</Emphasis>-triamminetrinitrorhodium(III) — β-<Emphasis Type="Italic">fac</Emphasis>-[Rh(NO<Subscript>2</Subscript>)<Subscript>3</Subscript>(NH<Subscript>3</Subscript>)<Subscript>3</Subscript>]

The paper describes the preparation techniques for β-fac-[Rh(NO₂)₃(NH₃)₃]. The complex crystallizes as colorless prisms belonging to the monoclinic crystal system. Crystal data: a = 6.6338(2) Å, b = 11.0627(3) Å, c = 11.5314(3) Å; β = 96.608(1)°, V = 840.64(4) ų, space group P2₁/n, Z = 4, d_calc = 2.308 g/cm³. The structure is molecular and contains neutral complex molecules having the fac configuration. Crystal chemical analysis of the complex in comparison to α-fac-[Rh(NO₂)₃(NH₃)₃] is performed.     

An EXAFS Study on Iron-Cobalt-Silica Nanocomposite Materials Prepared by the Sol-Gel Method

The structural evolution of FeCo-SiO₂ xerogel and aerogel nanocomposite samples during their sol-gel preparation have been studied by EXAFS (extended X-ray absorption fine structure) technique. Depending on the precursors of the alloy nanoparticles different intermediate are formed which have a strong influence on the formation of the FeCo alloy of the desired composition. The porous structure also plays an important role.     

Using Pseudoperiodicity for Polycrystal XRD Determination of the General Structural Motif of Coordination Compounds

This review summarizes experience in polycrystal diffractogram analysis for 100 coordination compounds using the translation sublattice isolation technique. The most widespread cases are described, and the general strategy of analysis is proposed. Conditions for transition from a rhombohedral sublattice to cubic lattices with different centerings are discussed.     

Pseudohalonium Ions: [Me3Si–X–SiMe3]+ (X=CN,OCN, SCN,and NNN)

By utilizing reaction mixtures, such as Me₃Si–X/[Me₃Si–X–SiMe₃]⁺ (X=CN, OCN, SCN, and NNN), it was possible to prepare the first examples of bissilylated pseudohalonium cations in high yields. The structure and bonding of a whole series of salts containing pseudohalonium cations is discussed on the basis of experimentally observed (X‐ray diffraction, Raman, and IR spectroscopy, and mass spectrometry) and theoretically obtained data. Salts containing pseudohalonium cations are only stable in the presence of weakly coordinating anions, such as the well‐known tetrakis(pentafluorophenyl)borate, [B(C₆F₅)₄]^?.