New binuclear ferrocenecarboxylates of rare-earth metals as precursors for ferrites: Syntheses,structures, and solid-phase thermolysis

New ferrocenecarboxylates of rare-earth metals, [Ln₂(μ-O,η²-OOCFc)₂(μ₂-O,O′-OOCFc)₂(η²-NO₃)₂(DMSO)₄] (Ln = Gd (I), Tb (II), and Y (III)) and [Gd₂(μ-O,η²-OOCFc)₂(η²-OOCFc)₄(DMSO)₂(H₂O)₂] · 2DMSO · 2CH₂Cl₂ (IV), are synthesized and characterized by X-ray diffraction analysis. Unlike all earlier known ferrocenecarboxylates of rare-earth metals, in isostructural compounds I–III the Ln atoms are linked by four bridging carboxyl residues, two of which are chelate-bridging (the coordination number of Ln is 9). Binuclear structure IV is formed by two chelate-bridging carboxylate ligands (the coordination number of Gd is 9). Weak antiferromagnetic and weak ferromagnetic interactions between the Gd atoms are observed in complexes I and IV, respectively. The thermal decomposition of the synthesized compounds is studied by differential scanning calorimetry and thermogravimetry. According to the X-ray diffraction data, the final thermolysis products of the complexes in air are garnets Ln₃Fe₅O₁₂.     

Hydrothermal synthesis and comparative coordination chemistry of new rare-earth V4+ compounds

Several new hydrated rare earth vanadates and rare earth oxy-vanadates have been synthesized using hydrothermal techniques and characterized using single crystal and powder X-ray diffraction and infrared and UV-vis absorption spectroscopies. The hydrated rare earth vanadates adopt the space group P2(1)/m with general formula A(3)VO(5)(OH)(3) (A = Y (1), Dy (2), or La (3)) and contain anionic distorted square pyramidal [VO(5)](-6) units and AO(7) and AO(8) polyhedra. The oxy-vanadates with the general formula A(2)O(VO(4)) (A = Y (4), Dy (5; 6), or Yb (7)) form two polymorphs in either P2(1)/c or C2/c space groups and contain anionic tetrahedral [VO(4)](-4) units and nonvanadium bonded O(2-) anions in distorted [OA(4)] tetrahedra. In all cases, the vanadium ion is in the tetravalent oxidation state, and its original source was the trace V(4+) impurities in YVO(4). The observed vanadyl and equatorial vanadium-oxygen bond lengths about the square pyramid in compounds 1-3 and the tetrahedral vanadium coordination found in compounds 4-7 are unusual for V(4+). The electronic and vibrational spectra are also reported and correlated with the appropriate coordination environment.     

Investigations on synthesis,thermolysis, and coordination chemistry of aminophosphine oxides

Some aminophosphine oxides (AmPOs), (R ₁)(R ₂)(R ₃)P=O [R ₁?=?R ₂?=?R ₃?=?HNCH₂CH=CH₂; R ₁?=?R ₂?=?Ph, R ₃?=?HNCH₂CH=CH₂; R ₁?=?R ₂?=?R ₃?=?HNNMe₂; R ₁?=?R ₂?=?Ph, R ₃?=?HNNMe₂; R ₁?=?R ₂?=?R ₃?=?NC₄H₈O; R ₁?=?R ₂₌Ph, R ₃?=?NC₄H₈O], have been synthesized. The coordination chemistry of these AmPOs is studied with La(III), Th(IV), and U(VI) salts. The products are characterized by various analytical and spectroscopic techniques, and the thermal properties of the ligands and their complexes examined. The TGA data for these compounds show different decomposition temperatures, as well as thermal stability of the metal complexes. Comparisons are made among different ligands on their selective complexing ability towards some chosen metal salts. Mulliken population analysis shows that the basicity of P=O of ligand increases with an increase in the number of P-bonded amino groups.     

A versatile solvent-free mechanochemical route to the synthesis of heterometallic dicyanoaurate-based coordination polymers

The solid-state mechanochemical method was proved to be a fast, simple, and efficient route to the synthesis of heterometallic [Au(CN)(2)]-based coordination polymers. Thus, a series of mixed-metal complexes, such as KCo[Au(CN)(2)](3), KNi[Au(CN)(2)](3), Cu(H(2)O)(2)[Au(CN)(2)](2), and Zn[Au(CN)(2)](2), was obtained by grinding stoichiometric amounts of K[Au(CN)(2)] and transition metal(II) chlorides. This solid-state method rapidly yields pure dicyanoaurate-based compounds, also in cases when the aqueous solution synthesis leads to an unseparable mixture of products. In addition, in some cases, the solid state reaction was faster than the corresponding solvent-based reaction. This mechanochemical method can be applied also to main group metals to obtain various cyanoaurate-based heterometallic coordination polymers, such as Me(2)Sn[Au(CN)(2)](2) and Ph(3)Sn[Au(CN)(2)]. For the 2:1 mixture of K[Au(CN)(2)] and Me(2)SnCl(2), the dramatic enhancement of the reaction rate by the presence of a minor amount of water was noticed. In Ph(3)Sn[Au(CN)(2)], as was revealed by single-crystal X-ray diffraction, each Ph(3)Sn unit is linked to two others by two Au(CN)(2) bridges via Sn-N bonds to form an infinite cyanide-bridged chain. There are no Au···Au contacts between the chains due to the sterical hindrance of the phenyl groups. A dehydrated blue Co[Au(CN)(2)](2) complex was obtained during grinding or heating of the moderate-pink Co(H(2)O)(2)[Au(CN)(2)](2) complex. This complex displays a vapochromic response when exposed to a variety of organic solvents, as well as water and ammonia vapors.     

New heterometallic coordination polymers derived form chalcogenocyanates: synthesis,characterization and electrical properties

A series of conducting mixed-metallic coordination polymers: Cu₂Pb(SCN)₄, CuPb(SeCN)₄, Cu^II _0.50Cu^IPb (SCN·SeCN)₂, CuAg(SCN)₂, CuAg(SeCN)₂ and CuAg(SCN·SeCN) have been synthesized by the reaction of Cu and Pb^II or Ag^Initrates with KSCN or KSeCN, or both KSCN and KSeCN in H₂O. Of significance are the aerobic reactions which yield heterometallic complexes viaoxidation of SCN^– and SeCN^– into (SCN)₂ and (SeCN)₂ followed by quantitative reduction of Cu^II into Cu^I; in the case of CuPb(SeCN)₄ reduction of Cu^II into Cu^I is not observed, while in Cu^{II 0.50}Cu^IPb(SCN·SeCN)₂, Cu^II is partially reduced to Cu^I. These compounds have been characterized by elemental (C, N, S and Se) analyses, magnetic moment measurements, relevant spectroscopies (i.r., far i.r., Raman, u.v.–vis. and e.p.r.), powder X-ray diffraction pattern and conductivity technique. The v(CN) vibrations in 2162–2087cm^–1 and far i.r. bands (500–100cm^–1) corroborated by Raman bands are conclusive of the bridging (N, S/Se) mode and metal-NCS and metal-SCN/SeCN^– bonding respectively in the complexes. Room temperature magnetic moment, electronic absorption spectra and e.p.r. active/silent nature confirm the oxidation state of copper in these solids. Room temperature compressed pellet conductivities _rt, 10^–9to 10^–7Scm^–1 with activation energies, E _a=0.19–0.25eV and increase in the conductivity with increase in temperature in the 305–423K, range and decrease in conductivity with decrease in temperature in the 295–200K range, show their semiconductor properties.     

Tetralones as precursors for the synthesis of 2,2′-disubstituted 1,1′-binaphthyls and related compounds

Using tetralones as starting materials, the synthesis of biaryl compounds is described in this paper. The tetralones were initially converted into 1-bromo-3,4-dihydro-2-naphthalenecarbaldehydes before effecting aromatization into the corresponding naphthalenes. These products were then subjected to Suzuki-Miyaura cross-coupling reactions, with a variety of aromatic boronic acids containing substituents in the ortho position, to afford biaryl compounds. The biaryl compounds possess heteroatom containing substituents ortho to the newly formed biaryl axis.     

Structurally diverse coordination compounds of zinc as effective precursors of zinc oxide nanoparticles with various morphologies

The structurally diverse coordination compounds of zinc were designed and synthesized using two types of building blocks: short‐chain carboxylate ions and hexamethylenetetraamine. They were characterized by X‐ray crystallography, infrared spectroscopy and thermal analysis. The studied compounds were used as precursors for production (via controlled thermal conversion) of zinc oxide nanoparticles. The conversion process was optimized in terms of two parameters (heating rate and maximum temperature). Such an approach, combined with proper design of the precursor structure, allows fabrication of various zinc oxide micro‐ and nanoparticles. The influence of a precursor structure and modifications of conversion parameters on size and morphology of ZnO particles were studied and discussed.     

Metals and coordination compounds as modifiers for epoxy resins

This review concentrates on the use of metals in the formulation of epoxy resin systems and the effect that this has on the physical and mechanical properties of the polymer system. Epoxy resins are one of the most important higher performance polymer systems in use today, ranging from simple two-part adhesives and sports equipment to high-tech applications such as formula one racing cars and the aerospace industry. Epoxy resins are capable of undergoing homopolymerisation, although this process generally yields products with inadequate properties for high-tech applications. Consequently, in many cases catalysts, additives and co-curing-agents are formulated with the epoxy resin to significantly increase the storage stability, decrease the cure time and improve the final properties. The use of metals to formulate resin systems with excellent storage stability is discussed, along with the use of coordination compounds to improve cured resin properties such as fracture toughness, thermal stability and water absorption, etc.     

The organic ligands as template: the synthesis, structures and properties of a series of the layered structure rare-earth coordination polymers

A series of new 2D-layered structural rare-earth coordination polymers with the general formal [Ln(C₈H₄O₅)(H₂O)₅]·(H₂O)·(C₈H₄O₅)_1/2 (Ln=Eu for (1); Gd for (2); Tb for (3); Dy for (4); and Er for (5)) have been yielded by hydrothermal synthesis. The coordination polymers crystallize in monoclinic space group C/2c with a=19.838(16), b=10.529(8), c=17.752(14) Å, β=107.503(14)° for (1), with a=19.823(7), b=10.552(4), c=17.762(6) Å, β=107.443(6)° for (2), with a=19.770(4), b=10.519(2), c=17.698(4) Å, β=107.52(3)° for (3), with a=19.632(2), b=10.492(2), c=17.617(3) Å, β=107.470(12)° for (4), with a=19.648(7), b=10.480(3), c=17.598(6) Å, β=107.502(6)° for (5), respectively. And the metal ions (Ln³⁺) are located in nine-member coordination environment. The carboxyl groups from 5-hydroxyisophthalate chelate the metal ions to form 1D helical cation chains. It is interesting that these helical cation chains are arranged to form 2D anion–cation layers by the uncoordinated ligands' anions as template. And the luminescence properties of the rare-earth ions are studied in the paper.     

Solvothermal synthesis and structures of three novel heterometallic microporous coordination polymers assembled from 2-hydroxy-nicotinic acid

Abstract  

Three novel heterometallic microporous coordination polymers {M(Hnico)₃M′} _n (1, M = Co, M′ = K; 2, M = Ni, M′ = K; 3, M = Co, M′ = Na, Hnico is the anion of 2-hydroxy-nicotinic acid, where the proton is transferred from the phenolate hydroxy group to the nitrogen atom of imine pyridine ring) were synthesized by hydrothermal reaction between M(Ac)₂·4H₂O, M′OH and a multifunctional organic aromatic H₂nico ligand and characterized by IR spectrum, elemental analysis, raman spectrum and the single crystal X-ray diffractions. In complexes 1–3, the M²⁺ ions linked three different Hnico ligand formed [M(Hnico)₃]⁻ subunit which further interlinked the six-coordination M′⁺ cation constructed 3D network. The network topology of 1–3 can be simplified a rare 3D (4,4)-connected (4¹²6³) net.     

Thermal solid state synthesis of coordination complexes from hydrogen bonded precursors

Thermal dehydrochlorination of crystalline 4-picolinium salts of [PtCl4]2- and [PdCl4]2- leads to formation of trans-[MCl2(4-picoline)2](M = Pt, Pd).     

Three-dimensional 3d-4f heterometallic coordination polymers: synthesis, structures, and magnetic properties

Three new 3d-4f heterometallic coordination polymers, [Ln(2)(H(2)O)(4)M(2)(H(2)O)(2)(QA)(5)].nH(2)O (H(2)QA = quinolinic acid; Ln = Gd, M = Ni, n = 7 (1); Ln = Gd, M = Co, n = 6.5 (2); Ln = Dy, M = Co, n = 6.5 (3)), have been synthesized through hydrothermal pretreatment and cooling-down crystallization. These compounds possess the isostructural 3D frameworks with 1D chairlike channels along the c axis, which are occupied by noncoordinating water molecules. Crystal data: for 1, C(35)H(41)Gd(2)Ni(2)N(5)O(33), orthorhombic, space group Pna2(1), with a = 28.567(6) A, b = 14.498(3) A, c = 12.250(2) A, and Z = 4; for 2, C(35)H(40)Gd(2)Co(2)N(5)O(32.5), orthorhombic, space group Pna2(1), with a = 28.843(3) A, b = 14.4325(13) A, c = 12.2275(9) A, and Z = 4; for 3, C(35)H(40)Dy(2)Co(2)N(5)O(32.5), orthorhombic, space group Pna2(1), with a = 28.8471(14) A, b = 14.4534(10) A, c = 12.2520(7) A, and Z = 4. The magnetic behaviors for the three compounds have been investigated.     

Hexadecapropyloxy-substituted diphthalocyanine complexes of rare-earth elements: synthesis,spectroscopic and electrochemical studies

Hexadecapropyloxy-substituted diphthalocyanine complexes of rare-earth elements (REE = Lu, Tm, Sm) were synthesized. The new symmetrically substituted diphthalocyanine complexes prepared starting from 4,5-dipropyloxyphthalodinitrile (phthalogen) are characterized by better solubilities compared to the known hexadecamethyl-substituted diphthalocyanine complexes of the same REE. Spectral and electrochemical characteristics of the complexes were studied. The compounds can be used as materials for high-contrast electrochromic devices.     

Kinetics of thermolysis of sterically hindered phenols used as polymeric material stabilizers

The thermolysis kinetics of a series of sterically hindered phenols was studied.     

Synthesis of N-methoxy-N-methyl-beta-enaminoketoesters: new synthetic precursors for the regioselective synthesis of heterocyclic compounds

[Structure: see text] Weinreb amides react with the lithium or sodium acetylide of ethyl propynoate in a hitherto unexplored acyl substitution-conjugate addition sequence to furnish (E)-N-methoxy-N-methyl-beta-enaminoketoesters. This approach provides a diverse entry to densely functionalized heterocyclic compounds, including pyrazoles through regioselective cyclocondensations with hydrazines in a microwave-assisted reaction.     

δ-Nitroalkanols as precursors for the one-pot synthesis of substituted tetrahydrofurans

DBU catalyses the one-pot Michael addition of nitroalkanes to 1,4-dienone derivatives, elimination of nitrous acid, then intramolecular conjugate addition-ring closure to allow the direct formation of a variety of tetrahydrofurans.