Solid-state 31P MAS NMR Spectroscopy Research Articles

An investigation of the phosphate removal mechanism by MgFe layered double hydroxides

The phosphate adsorption properties including kinetics and uptake pathway of MgxFe layered double hydroxides (LDH) with targeted x values of 2 and 3 and intercalated with nitrate (NO3−) and chloride (Cl−) anions were investigated at a phosphate concentration of 16.31 mgP·L−1 and pH (pH = 5, 7, and 9) similar to wastewater conditions. The synthesized MgxFe-LDH show fast adsorption (90–98%) of the final phosphate removal within 3 h and remove 68–73% of the total phosphate content after 24 h. The pristine MgxFe-LDH and solid products after phosphate exposure were characterized by PXRD, FT-IR, zeta-potential, SEM, and solid-state 31P MAS NMR spectroscopy to investigate the phosphate removal pathway. Interestingly, the four MgxFe-LDH phase had similar Mg:Fe ratios irrespective of the Mg:Fe ratio of the reactants based on PXRD. The MgxFe-LDH plate-like morphology was preserved after phosphate exposure and no sign of phosphate intercalation were evident by PXRD, FT-IR, and SEM albeit a small amount of the MgxFe LDH was dissolved based on ICP-OES, PXRD and the final pH. Partial dissolution of the LDH was clearly evident by SEM for Mg2Fe-LDH exposed to 200% theoretical P capacity. The FT-IR spectra and zeta-potential values indicated that the phosphate ions are adsorbed by surface complexation. The 31P MAS NMR spectra of MgxFe-LDH exposed to phosphate has an intense spinning sideband manifold and only minor paramagnetic shifts (<30 ppm) are observed. Thus, phosphate is in the proximity of iron, but not directly bound to the paramagnetic iron via Fe-O-P bond (inner-sphere complexation or mineralization). Thus, the dominating phosphate uptake pathway by MgxFe-LDH is surface complexation similar to MgAl-LDH and possible the formation of ill-defined magnesium phosphate due to partial dissolution of the MgFe-LDH, especially at high P loading.

ChemInform Abstract: Synthesis and Structure of the Phosphorane P(CH2Cl)Cl4.

The compound P(CH2Cl)Cl4, which is molecular in the liquid phase, has been shown by solid-state 31P MAS NMR spectroscopy to have the structure [P(CH2Cl)Cl3]+[P(CH2Cl)Cl5]–; this is the first example of an organochlorophosphorane having a structure like that of solid [PCl4]+[PCl6]–.

Immobilization of platinum(ii) and palladium(ii) complexes on metal oxides by sol–gel processing and surface modification using bifunctional phosphine–phosphonate esters

The bifunctional phosphine–phosphonate ester derivatives Ph2P(CH2)3P(O)(OSiMe3)2 (L), (cis-Cl2Pt[Ph2P(CH2)3P(O)(OSiMe3)2]2 (1), trans-Cl2Pd[Ph2P(C6H4)P(O)(OSiMe3)2]2 (2) and trans-Cl2Pd[Ph2P(C6H4)P(O)(OEt)2]2 (3) were used to immobilize platinum(II) and palladium(II) complexes on metal oxide supports by three different routes: sol–gel incorporation of L in TiO2 or ZrO2 matrices followed by complexation with PtCl2(PhCN)2, direct sol–gel immobilization of 1 and 2, surface modification of TiO2nanoparticles with 2 and 3. The hybrid solids were characterized by solid-state 31P MAS NMR spectroscopy, surface area measurements and chemical analysis; the advantages and disadvantages of the different routes were discussed. This study demonstrates that phosphonic esters can provide a valuable alternative to phosphonic acids for the preparation of functional organic–inorganic hybrids based on metal oxides.

Au3SnP7@Black Phosphorus: An Easy Access to Black Phosphorus.

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Au3SnP7@Black Phosphorus: An Easy Access to Black Phosphorus

Black phosphorus can be prepared under low-pressure conditions at 873 K from red phosphorus via the addition of small quantities of gold, tin, and tin(IV) iodide. Au3SnP7, AuSn, and Sn4P3 were observed as additional phases. Tin(IV) iodide remains unreacted during the preparation process. The crystal structure of black phosphorus was redetermined from single crystals. P (295 K): a = 3.316(1) A, b = 10.484(2) A, c = 4.379(1) A, V = 152.24(6) A3, space group Cmce (No. 64). Solid-state 31P MAS NMR spectroscopy and X-ray powder diffraction were performed to substantiate the high crystal quality of black phosphorus. A possible mechanism for the formation is discussed in terms of the comparable structural features of black phosphorus and Au3SnP7. Thermodynamic calculations showed that the only relevant gas-phase species, P4, and the transport reactions are not suitable for the preparation of orthorhombic black phosphorus at temperatures above 773 K. A kinetically controlled mechanism must be favored instead of a thermodynamically controlled formation. The new preparation method of black phosphorus represents an easy and effective way to avoid complicated preparative setups, toxic catalysts, or "dirty" flux methods and is of general interest in elemental chemistry.

Dimolybdenum(III) Complexes of −OSi(OtBu)3, −O2P(OtBu)2, and −OB[OSi(OtBu)3]2as Single-Source Molecular Precursors to Molybdenum-Containing, Multi-Component Oxide Materials

The following dimolybdenum complexes containing −OSi(OtBu)3, −O2P(OtBu)2, and −OB[OSi(OtBu)3]2 ligands have been synthesized and structurally characterized: Mo2(NMe2)4[OSi(OtBu)3]2 (1), Mo2(OtBu)4[OSi(OtBu)3]2 (2), Mo2(NMe)4{OB[OSi(OtBu)3]2}2 (3), Mo2(NMe2)2[μ-O2P(OtBu)2]2[O2P(OtBu)2]2 (4), Mo2(NMe2)2[OSi(OtBu)3]2[μ-O2P(OtBu)2]2 (5), and Mo2(NMe2)2[μ-O2P(OtBu)2]2{OB[OSi(OtBu)3]2}2 (6). The isolation and structural characterization of trans- and cis-isomers of complexes 4 and 5 (4a and 4b, 5a and 5b, respectively) are also reported. Studies of the thermal decompositions of the complexes (by thermogravimetric analysis and solution 1H NMR spectroscopy) were performed. Xerogels with approximate compositions of 2MoO1.5·2P2O5 and 2MoO1.5·2P2O5·2SiO2 were derived from 4a and 5a or 5b, respectively, via solution thermolyses (toluene). The as-synthesized (and dried) xerogels contain one equiv of HNMe2 per molybdenum center (by combustion analysis, IR spectroscopy, and thermogravimetric analysis), and these materials have high surface areas (up to 270 m2 g-1). Upon calcination at 300 °C, the coordinated amines are lost and the surface areas are significantly reduced (to 40 m2 g-1 and <5 m2 g-1 for the materials derived from 4 and 5a or 5b, respectively). Solid-state 31P MAS NMR spectroscopy suggests that the as-synthesized xerogels retain structural features of the starting molecular precursors, as indicated by the presence of resonances that correspond to both bridging and terminal −O2P(OtBu)2 ligands. Upon calcination at 300 °C, the resonances for bridging −O2P(OtBu)2 groups are replaced by those for PO43-. The material derived from 4 exhibits low activity and poor selectivity for the oxidative dehydrogenation (ODH) of propane to propylene. Cothermolyses of 4 and Bi[OSi(OtBu)3]3 resulted in formation of Bi/Mo/P/Si/O materials with improved performance for the ODH of propane.

Solvent-free mechanochemical synthesis of two Pt complexes: cis-(Ph3P)2PtCl2 and cis-(Ph3P)2PtCO3.

Cis-(Ph3P)2PtCl2 and cis-(Ph3P)2PtCO3 were prepared mechanochemically from solid reactants in the absence of a solvent; cis-(Ph3P)2PtCl2 was obtained in 98% yield after ball-milling of polycrystalline PtCl2 and Ph3P; the mechanically induced solid-state reaction of cis-(Ph3P)2PtCl2 with an excess of anhydrous K2CO3 produced cis-(Ph3P)2PtCO3 in 70% yield; the formation of transition metal complexes as a result of mechanochemical solvent-free reactions has been confirmed by means of solid-state 31P MAS NMR spectroscopy, X-ray powder diffraction and differential thermal analysis.

Synthesis and Characterization of the Phosphorus Halide−Boron Halide Complexes X3PBY3 (X = Cl, Br, I; Y = Br, I) by31P MAS NMR, IR, and Raman Spectroscopy and the Crystal Structure of Br3PBBr3

The phosphorus halide−boron halide complexes X3PBY3 (X = Cl, Br, I; Y = Br, I) were prepared and characterized by Raman and IR spectroscopy. Density functional theory (B3LYP) was applied to calculate structural and vibrational data. Assignments of the vibrational normal modes for these Lewis acid−base adducts were made on the basis of their Raman and IR spectra in comparison with computational results. The compounds Cl3PBBr3, Br3PBBr3, I3PBBr3, and I3PBI3 were also studied by solid-state 31P MAS NMR spectroscopy. Second-order 31P−79,81Br dipolar coupling effects were observed in the 31P MAS NMR spectrum of Br3PBBr3. The molecular structure of Br3PBBr3 was determined by X-ray diffraction.

Synthesis and Crystal Structure of the Organically Templated Open Framework Magnesium Phosphate UiO-20 with DTF Topology

The synthesis and crystal structure of Mg4(PO4)4·2C2H10N2 (UiO-20), which is the first example of an organically templated open framework magnesium phosphate, is described. UiO-20 is characterized by means of single-crystal and powder X-ray diffraction, solid-state 31P MAS NMR spectroscopy, and thermogravimetric analysis. Crystal data for UiO-20: space group C2/c (no. 15); a = 20.9098(8) Å, b = 17.8855(7) Å, c = 14.7913(6) Å; γ = 134.842(2)°; V = 3922.3(3) Å3; and Z = 8. The framework topology is of zeolite type DFT, and UiO-20 is isostructural with compounds such as the cobalt phosphate DAF-2, zinc phosphate DAF-3, zinc arsenate UCSB-3ZnAs, and gallium germanate UCSB-3GaGe. The structure has a 3D 8-ring channel system with protonated ethylenediammonium cations in the channel junctions. The material turns amorphous upon removal of the organic template on heating.

Grafting of alumina by diphenylphosphinate coupling agents

ABSTRACTAlumina particles were treated under various conditions with different diphenylphosphinate compounds: diphenylphosphinic acid, ethyl diphenylphosphinate, and trimethylsilyl diphenylphosphinate. The balance between surface complexation (namely grafting) and surface phase transformation (formation of bulk aluminum phosphinate phase) was investigated by IR and solid-state 31P MAS NMR spectroscopy, using the model crystalline phase Al(O2PPh2)3 synthesized in a parallel work as a reference. Satisfactory grafting was obtained either by using diphenylphosphinic acid in aqueous medium at pH about 6, or by using ethyl diphenylphosphinate in organic medium as coupling agents.

Synthesis and ab-initio structure determination of organically templated magnesium phosphates from powder diffraction data

NH4MgPO4·H2O (dittmarite), 0.5·[NH3(CH2)2NH3]2+[MgPO4·H2O]− (UiO-24-EN) and 0.5·[NH3(CH2)4NH3]2+[MgPO4·H2O]−·H2O (UiO-24-DAB) were prepared by hydrothermal methods, and their structures were determined ab-initio from powder diffraction data. The three compounds are composed of inorganic magnesium phosphate layers separated by charge compensating ammonium or organic cations and water molecules. Corner sharing magnesium octahedra crosslinked by phosphate tetrahedra form the inorganic layers in dittmarite. This atomic arrangement is identical in the UiO-24 type of compounds, and these structures can be viewed as dittmarite being intercalated by diamines and water molecules. The compounds have been characterized by thermogravimetric analysis, solid-state 31P MAS NMR spectroscopy and ion exchange experiments.

Hydrothermal treatment and strontium ion sorption properties of fibrous cerium(IV) hydrogenphosphate

Fibrous cerium hydrogenphosphate, CeP, has been treated hydrothermally in 1 mol dm -3 phosphoric acid solution. CEP and its hydrothermally treated product, CeP(HT), have been characterized by X-ray powder diffractometry, scanning electron microscopy, solid-state 31 P MAS NMR spectroscopy, FTIR spectroscopy, chemical and thermal analyses. A poorly crystalline fibrous CeP with a d-spacing of 1.1 nm converted into a highly crystalline CeP(HT) with platelet morphology by hydrothermal treatment. Solid-state 31 P MAS NMR and FTIR measurements confirmed that one kind of phosphate (H 2 PO 4 ) is present in CeP and two kinds of phosphate (HPO 4 , PO 4 ) are present in CeP(HT), in which the integrated intensity ratio of HPO 4 to PO 4 is 2:1. From chemical and thermal analyses, structural formulae for CeP and CeP(HT) are assumed to be CeO(H 2 PO 4 ) 2 2H 2 O and Ce(HPO 4 ) (PO 4 ) 0.5 (OH) 0.5 , respectively. The Na + exchange capacity of CeP amounted to 4.5 mmol g -1 at pH 11 while that of CeP(HT) was less than 1.0 mmol g -1 in the pH range 2–12. The pH dependence of the metal ion distribution coefficients exhibited ideal ion-exchange behaviour on CeP while metal ion distribution coefficients on CeP(HT) scarcely depended on pH. The metal ion selectivities of CeP and CeP(HT) increased in the order: Na + <Ca 2+ <Sr 2+ <K + , and Na + <K + <Ca 2+ <Sr 2+ , respectively. The distribution coefficient for the Sr 2+ ion of CeP(HT) was higher than that of CeP under hydrothermal conditions.

Synthesis and structure of the phosphorane P(CH2Cl)Cl4

The compound P(CH2Cl)Cl4, which is molecular in the liquid phase, has been shown by solid-state 31P MAS NMR spectroscopy to have the structure [P(CH2Cl)Cl3]+[P(CH2Cl)Cl5]–; this is the first example of an organochlorophosphorane having a structure like that of solid [PCl4]+[PCl6]–.