A new method for the synthesis of organic–polyoxometallate hybrid compounds

The reaction of the Na₂MoO₄ or Na₂WO₄ salt with organic amine and PCl₅, SiCl₄ or TiCl₄ in hydrochloric acid medium under hydrothermal conditions yields organic–polyoxometallate hybrid compounds, with the following reaction formula: Na₂MO₄ + Lewis-base + XCl_n + HCl → (Lewis-baseH)_m(XM₁₂O₄₀) + NaCl + H₂O (M = Mo or W; X = P, Si, Ti,; n = 3–5). By using this method, four new complexes, [(CH₃)₂NH]₃[H₃PW₁₂O₄₀] (1), (C₂H₅OH)₃(H₃PMo₁₂O₄₀) (2), [DMDA]₂[H₄SiW₁₂O₄₀]·H₂O (3) (DMDA = 1 N,3 N-dimethyl-1,3-diazolidine) and [(DAN)₆][H₄TiW₁₂O₄₀]·4H₂O (DAN = 4,4′-dianiline) (4), were obtained, and their crystal structures are reported. Thermal analysis of 1, 2 and 4 has been carried out. The thermal analysis indicates that the Keggin anion skeleton begins to decompose at about 300 °C. The possibility of constructing hydrogen-bond interactions by association between the polyoxometallate and the organic compound is explored. The roles of solvents and organic groups in the formation of specific crystalline architectures are discussed. The crystal structure of [H₄TiW₁₂O₄₀], a hetero-transition-metal Keggin polyoxometallate with a square-plane TiO₄, has been reported. Four architectures developed by hydrogen-bond associations of different Keggin polyoxometallates and organic bearing N–H or O–H donor functions are described. The selected organic modules (4,4′-dianiline, 1,3-dimethylimidazolidine, dimethylamine and ethanol) possess hydrogen-donor functions to allow them to act as bridges between polyoxometallate groups. Depending on the nature of the donor group, the number of hydrogens available for bonding, the geometric features and the sizes of the organic modules, diverse assembling patterns have been observed ranging from one-dimensional to three-dimensional networks. For all the networks, H₃O⁺ and H⁺ act as actual linkers between the molecular units.     

Syntheses,crystal structures,and magnetic and luminescent properties of a series of lanthanide coordination polymers with chelidamic acid ligand

A series of lanthanide(III) complexes with chelidamic acid ligand, [Ln(C₇H₂NO₅)·3H₂O]_n·nH₂O (Ln = La (1), Y (2), Sm (3), and Nd (4)), [Gd₂(C₇H₂NO₅)₃·4H₂O]_n·2nH₂O (5) and [Ce(C₇H₂NO₅)·1.5H₂O]_n (6), have been synthesized by hydrothermal method and structurally characterized by single-crystal X-ray diffraction. Complexes 1–4 are isostructural and possess 2D framework. Complex 5 contains two different Gd(III) ions linked through carboxylate group to form a 2D framework. Complex 6 exhibits a (4⁴) topology 2D network. The variable-temperature magnetic properties of 3 and 5 have been investigated. Furthermore, the photoluminescent properties of 1, 2, 3, and 5 at room temperature were also studied.     

Syntheses,structures, photoluminescences of silver(I) coordination polymers with 2-aminopyrazine and varied dicarboxylate ligands

Four new silver(I) coordination polymers, namely [Ag(NH₂pyz)(ox)_0.5]_n (1), [Ag(NH₂pyz)(adp)_0.5·2H₂O]_n (2), [Ag₂(NH₂pyz)₂(bdc)·H₂O]_n (3) and [Ag₂(NH₂pyz)_2.5(ndc)]_n (4) [NH₂pyz = 2-aminopyrazine, ox = oxalate anion, adp = adipate anion, bdc = 1,4-benzenedicarboxylate anion, ndc = 1,4-naphthalenedicarboxylate anion] have been synthesized by solution phase ultrasonic reactions of Ag₂O with heterocyclic NH₂pyz and various dicarboxylates under ammoniacal conditions. The complexes were characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Complex 1 is a three-dimensional (3D) framework with an α-ThSi₂ topology. Complex 2 features a 2D 4⁴-sql net involving infinite 1D double Ag-NH₂pyz chains and flexible adp anion spacers. Complex 3 is a 3D framework in which 1D single Ag-NH₂pyz chains are pillared by bdc anions to form a 2D 6³-hcb network, adjacent 2D networks are packed into a 3D framework through bridging O atoms of dbc anions. Complex 4 is a 2D structure built from infinite 1D stair-like chains containing finite Ag₄(NH₂pyz)₅ subunits. The results show that the structural diversity of the complexes result from the nature of the dicarboxylate ligands. The photoluminescence properties of the complexes were also investigated in the solid state at room temperature.     

Structural characterization of methanol substituted lanthanum halides

The first study into the alcohol solvation of lanthanum halide [LaX₃] derivatives as a means to lower the processing temperature for the production of the LaBr₃ scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H₂O)₇](Br)₂}₂ (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H₂O)₇(MeOH)₂](Br)₃ (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH₂, crystals of [Ca(MeOH)₆](Br)₂ (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr_2.75·5.25(MeOH)]^+0.25 [LaBr_3.25·4.75(MeOH)]^−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr₃ in MeOH forming the 8-coordinated [LaBr₃(MeOH)₅] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX₃ derivatives were isolated as [(MeOH)₄(Cl)₂La(μ-Cl)]₂ (6) and [La(MeOH)₉](I)₃·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (¹³⁹La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4–6 were slightly higher in comparison to their hydrated counterparts.     

Microwave-assisted and conventional synthesis and stereogenic properties of monospirocyclotriphosphazene derivatives

The reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆, with N/O donor type N-alkyl or (aryl)-o-hydroxybenzylamines HO(C₆H₄)CH₂NHR(Ar), [R(Ar) = C(CH₃)₃ (1), Ph (2)] produce monospirocyclic tetrachlorocyclotriphosphazenes (1a and 2a). The geminal substituted cyclotriphosphazenes (1b, 1d, 2b and 2d) are obtained from the reactions of 1 equiv. of 1a and 2a with 2 equiv. of pyrrolidine or morpholine in THF, while the fully substituted phosphazenes (1c, 1e, 2c and 2e) are formed from the reactions of 1a and 2a with the excess pyrrolidine or morpholine in toluene, between 24 and 48 h. The microwave-assisted reactions of 1a and 2a with excess pyrrolidine or morpholine in toluene afford the fully substituted products with higher yields than those which were obtained by conventional methods. The structural investigations of the compounds have been verified by elemental analyses, ESI-MS, FTIR, ¹H, ¹³C, ³¹P NMR and HETCOR techniques. The crystal structure of 2a is determined by X-ray crystallography and the phosphazene ring is in the flattened boat form. Compounds 1b, 1d, 2b and 2d in which the spiro aryloxy moiety provides the one centre of chirality exist as racemates and the chirality has been confirmed by ³¹P NMR spectroscopy on addition of a chiral solvating agent (CSA), (S)-(+)-2,2,2-trifluoro-1-(9′-anthryl)ethanol.     

Solvent-dependent formation of two different Cd(II) complexes with p-BrC6H4C(S)NHP(O)(OiPr)2 (HL). Crystallographic modification of Cd(HL)2L2

Reaction of the potassium salt of N-(diisopropoxyphosphoryl)-p-bromothiobenzamide p-BrC₆H₄C(S)NHP(O)(OiPr)₂ (HL) with Cd(II) cations in freshly dried and distilled EtOH leads exclusively to the complex [Cd(p-BrC₆H₄C(S)NH₂-S)(L-O,S)₂] ([Cd(L^I)L₂]), while the same reaction in H₂O leads to the complex [Cd(HL-O)₂(L-O,S)₂] ([Cd(HL)₂L₂]). The corresponding reactions with Zn(II) always lead to the complex [Zn(L-O,S)₂] ([ZnL₂]) regardless of the solvent. The crystal structure of [Cd(HL)₂L₂]^.2/3H₂O reveals to be a polymorph to the previously reported anhydrous [Cd(HL)₂L₂].     

Complexes of 4- and 5-bromo derivatives of 2-(hydroxymethyl)pyridine with copper(II) and cobalt(II) salts. Synthesis and X-ray crystal structures

Four copper(II) complexes (1–4) and a cobalt(II) complex (5) derived from 4-bromo-2-(hydroxymethyl)pyridine (L¹) or 5-bromo-2-hydroxymethyl)pyridine (L²) with Cu(NO₃)₂·3H₂O, CuCl₂·2H₂O and CoCl₂·6H₂O have been synthesized and their respective crystal structures studied. They show specific influences owing to the different kind of metal cations and counter anions, the hydration as well as the different position of the bromine substitution on both the coordination of the complex unit and the network structure of the crystal lattice. The Cu(II) complexes of L¹ are five-coordinate [Cu(L¹)₂NO₃]NO₃·H₂O (1) and [Cu(L¹)₂Cl]Cl·H₂O (2) species with distorted quadratic pyramidal and trigonal bipyramidal coordination geometries of the N₂O₃ and N₂O₂Cl donor atoms around the Cu(II), respectively. The Cu(II) complexes of L² are six-coordinate [Cu(L²)₂(NO₃)₂] (3) and [Cu(L²)₂Cl(H₂O)]Cl·H₂O (4) species with distorted octahedral coordination geometries of the N₄O₂ and N₂O₃Cl donor atoms. A distorted octahedral coordination geometry of the N₂O₂Cl₂ donor atoms is also found in the complex unit [Co(L²)₂Cl₂] of the Co(II) complex 5 but showing the oxygen atoms of the chelating ligand as well as the chloride ions in a cis-position. Depending on the complex, water molecules and chloride anions are shown to act as stabilizing components of the crystal structure. The comparative structural investigation includes also known structures of the bromine-free ligand analogue 2-(hydroxymethyl)pyridine, illustrating the basic implication of the bromine substitution, mostly perceptible in the different modes of crystal packing.     

Synthesis,crystal structures and spectroscopic studies of praseodymium(III) malonate complexes

Reactions of malonic acid (H₂mal) with PrCl₃·6H₂O afforded the known complex [Pr₂(mal)₃(H₂O)₆]_n (1), and compounds [Pr₂(mal)₃(H₂O)₆]_n·2nH₂O (2·2nH₂O), [PrCl(mal)(H₂O)₃]_n·0.5nH₂O (3·0.5nH₂O) and [Pr(mal)(Hmal)(H₂O)₃]_n·nH₂O (4·nH₂O) using various reaction ratios, reaction media (H₂O, MeOH) and pH values. Analogous reactions with CeCl₃·7H₂O afforded compounds [Ce₂(mal)₃(H₂O)₆]_n (5), [CeCl(mal)(H₂O)₃]_n·nH₂O (6·nH₂O) and [Ce(mal)(Hmal)(H₂O)₃]_n·nH₂O (7·nH₂O). Compounds 2·2nH₂O and 3·0.5nH₂O were characterized by X-ray crystallography, and 4–7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1–3, i.e., the μ₂-κO:κO′:κO″ and the μ₄-κ²O:κO′:κ²O″:κO? in 1 and 2 leading to a 3D network structure, and the μ₃-κ²O:κO′:κ²O″:κO? in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5nH₂O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1–3 are discussed in terms of known malonato(-2) Ln^III and Ca^II complexes. The bioinorganic chemistry relevance of our results is discussed.