The coordination chemistry of N , N ′-dimethylpropyleneurea (dmpu) coordinated metal ions and complexes is reviewed. Dmpu is space-demanding at coordination forcing most metal ions and complexes to adopt lower coordination numbers than in most cases.

The solvation and coordination chemistry of the manganese(II) ion in water, methanol, dimethylsulfoxide (dmso), N,N'-dimethylpropylene urea (dmpu), acetonitrile and N,N-dimethylthioformamide (dmtf) have been studied from solvation thermodynamic, structural and complex formation ability point of view by calorimetry and EXAFS spectroscopy. The heats of transfer from water to methanol, dmso, acetonitrile and dmtf have been determined to -37.7, -71.6, -23.1 and -36.3 kJ mol(-1), respectively, from the heats dissolution of anhydrous manganese(II) tri-fluoromethanesulfonate by ampoule calorimetry in the neat solvents. Refinement of the EXAFS data of the hydrated and methanol and dmft solvated manganese (II) ions in solution show octahedral configuration and mean Mn-O bond distances of 2.165(3), 2.161 (2) and 2.157(3) angstrom, respectively. The Mn-O bond distance is significantly shorter in dmpu solution, 2.087(3) angstrom. As dmpu is a space-demanding solvent upon coordination, the manganese(II) ion is only allowed to bind five dmpu molecules in the solvate complex. The acetonitrile solvated manganese(II) ion is six-coordinate in octahedral fashion in solution with a mean Mn-N bond distance of 2.193(3) angstrom. The relative permittivity of pyridine is too low to allow dissociation of salts of divalent metal ions and neutral pyridine solvated complexes are formed in pyridine solution. In concentrated manganese(II) trifluoromethanesulfonate dmtf solution a contact ion-pair is formed with one trifluoromethanesulfonate ion. In this complex manganese(II) binds five dmtf molecules and a trifluoromethanesulfonate oxygen with Mn-S and Mn-O bond distances of 2.598(6) and 2.16(1) angstrom, respectively, in an octahedral complex. Complex formation studies performed by titration calorimetry of the manganese(II)-bromide system show significantly more stable complexes in dmpu than in solvents where the solvated manganese(II) ion has regular octahedral symmetry. The dmpu solvated MnBr2 complex in dmpu solution is five coordinate with mean Mn-Br and Mn-O bond distances of 2.494(3) and 2.076(3) angstrom, respectively. The structure of the [MnBr2(dmpu)(2)] complex in solid state has distorted tetrahedral geometry with mean Mn-Br and Mn-O bond distances of 2.473(3) and 2.014(3) angstrom, respectively, and a Br-Mn-Br bond angle of 116.3(1) degrees. (C) 2021 Elsevier Ltd. All rights reserved.

Colloids and nanoparticles leached from agricultural land are major carriers of potentially bioavailable nutrients with high mobility in the environment. Despite significant research efforts, accurate knowledge of macronutrients in colloids and nanoparticles is limited. We used multi-elemental synchrotron X-ray fluorescence (XRF) microscopy with multivariate spatial analysis and X-ray atomic absorption near-edge structure (XANES) spectroscopy at the P and S K-edges, to study the speciation of P and S in two fractions of leached particles, >0.45 and <0.45 µm respectively, collected from four tile-drained agricultural sites in Sweden. P K-edge XANES showed that organic P, followed by P adsorbed to surfaces of aluminum-bearing particles were the most common forms of leached P. Iron-bound P (Fe-P) forms were generally less abundant (0-30 % of the total P). S K-edge XANES showed that S was predominantly organic, and a relatively high abundance of reduced S species suggests that redox conditions were adverse to the persistence of P bound to Fe-bearing colloids in the leachates. Acid ammonium-oxalate extractions suggested that P associated with Al and Fe (Al-P and Fe-P) in most cases could be explained by the adsorption capacity of non-crystalline (oxalate-extractable) oxides of Al and Fe. These results improve our understanding of particulate P and S speciation in the vadose zone and helps in developing effective technologies for mitigating colloidal driven eutrophication of water bodies near agricultural land.

The structures of the solvated copper(II) ion in water and nine organic oxygen donor solvents with similar electron-pair donor ability, but with different space-demanding properties at coordination, have been studied by EXAFS. N,N'-Dimethylpropyleneurea and N,N,N',N'-tetramethylurea are sufficiently space demanding at coordination to make the axial positions not accessible, resulting in square-planar copper(II) solvate complexes with an intense green color. The mean Cu-O bond distances in these two solvate complexes are 1.939(3) and 1.935(3) Å, respectively. The best fits of the remaining solvates, which are light blue in different hues, are obtained with a Jahn-Teller distorted-octahedral model consisting of four strongly bound solvent molecules in the equatorial positions at 1.96(2) Å and two in the axial positions but with different Cu-Oax bond distances: ca. 2.15 and 2.32 Å. This is in agreement with observations in solid-state structures of compounds containing hexaaquacopper(II) complexes crystallizing in noncentrosymmetric space groups and all reported crystal structures containing a [Cu(H2O)5(O-ligand)] complex with Jahn-Teller distortion. Such a structure is in agreement with previous EPR and EXAFS studies proving the hydrated copper(II) ion to be a noncentrosymmetric complex in aqueous solution. The refinements of the EXAFS data of the solids [Cu(H2O)6](ClO4)2, [Cu(H2O)6](BrO3)2, [Cu(H2O)6]SiF6, Cu(NO3)2·2.5H2O, and CuSO4·5H2O gave Cu-O bond distances significantly different from those reported in the crystallographic studies but similar to the configuration and bond distances in the hydrated copper(II) ion in aqueous solution. This may depend on whether the orientation of the axial positions is random in one or three dimensions, giving a mean structure of the solid with symmetry higher than that of the individual complexes. This study presents the very first experimental data from the new X-ray absorption spectroscopy beamline Balder at the MAX IV synchrotron radiation facility in Lund, Sweden, as well as the utilized properties of the beamline.

A very slow oxidation of dimethylsulfoxide (dmso) solvated tin(ii) ions in solution results in the formation of a crystalline, structurally determined compound, [CH3Sn(OS(CH3)2)5](ClO4)3, whereas a similar reaction in N,N-dimethylthioformamide (dmtf) forms a crystalline solid with a proposed binuclear [Sn2(SH)2(SCHN(CH3)2)8]6+ entity but whose exact formula remains undetermined. Both solids precipitate with time in their respective mother liquids and constitute the first two tin(iv) and even tetravalent d10 metal ion solvate complexes ever reported. An EXAFS study showed that the structure of the [CH3Sn(OS(CH3)2)5]3+ complex is identical in solid state and dmso solution. While the exact chemical reaction pathways are unknown, the formation of these complexes constitute a novel way of obtaining solvated tin(iv) ions in standard, commonplace organic media.

The K-edge X-ray absorption near-edge structure (XANES) spectra of 19 phosphorus-containing compounds have been measured in solution. The energy at maximum intensity of the primary phosphate peak, regardless of chemical species, is 2154.5 +/- 0.4 eV. A few of the compounds studied feature XANES spectra which are conceivably characteristic enough to be used as positive identifiers in solution, including O,O-diethyldithiophosphate, (C2H5O)(2)PS(SH), triphenylphosphine oxide, (C6H5)(3)PO, and triphenylphosphite (C6H5O)(3)P. However, most spectra are near-identical or similar enough to another compound to prohibit any useful quantification analysis. The narrow range of absorption edge energy, and all phosphorus compounds studied have an absorption edge at higher energy than elemental phosphorus (red phosphorus). This shows that the electron density of phosphorus in these compounds is lower than in elemental phosphorus, and the conventional use of oxidation numbers cannot be applied. (C) 2018 Published by Elsevier B.V.

Recent research suggests that Swedish organic arable soils have been under-recognized as a potential source of phosphorus (P) loading to water bodies. The aim of this study was to compare P losses through leaching from organic and high-fertility mineral soils. In addition, the effectiveness of a magnesium-salt-coated biochar applied below the topsoil as a mitigation strategy for reducing P losses was evaluated.

The use of replacement lanthanoid ions in actinoid chemistry is commonplace, which requires a full understanding of the similarities and differences between the two series. This overview lists, compares and discusses the available crystallographic data for N-donors for the lanthanoids and the actinoids using their trivalent state as a natural starting point for comparison.

The structures of the N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), and N,N-dimethylpropionamide (dmp) solvated strontium and barium ions have been determined in solution using large angle X-ray scattering and EXAFS spectroscopy. The strontium ion has a mean coordination number (CN) between 6.2 and 6.8, and the barium ion has a mean CN between 7.1 and 7.8 in these amide solvents. The non-integer numbers indicates that equilibria between different coordination numbers and geometries exist in these systems. Structural information of the alkali, alkaline earth, and selected transition metal and lanthanoid(iii) ions, and the halide ions in water, methanol, ethanol, dimethylsulfoxide, formamide, dmf and dma has been combined with previously reported standard partial molar volumes, V0. The ionic radii and charge densities (charge/ionic volume), and corresponding V0 values have been used to gain information on the relationship between structural and volumetric properties. For the structure-breaking ions, i.e. the alkali metal and halide ions, there is an almost linear relationship between the ionic radius and V0. On the other hand, for the structure-making ions, here the alkaline earth, transition metal and lanthanoid(iii) ions, a linear relationship is observed between the charge density and V0. Solvents with a well-defined bulk structure through hydrogen bonding, specifically, water, methanol and ethanol, will be more contracted through solvation than aprotic solvents, as the space between the solvent molecules is lost as a result of the hydrogen bonding. In this respect, methanol stands out as the most compressed solvent participating in solvation compared to its bulk structure.

The coordination chemistry of oxotitanium(IV) or titanyl(IV), TiO 2+ , has been studied in solution by X-ray methods. The titanyl(IV) ion hydrolyzes easily in aqueous systems to solid titanium dioxide as long as it is not stabilized through complexation. In this study the structures of the hydrated bissulfatotitanyl(IV) complex and the dimethylsulfoxide (DMSO) solvated titanyl(IV) ions have been determined. In isolated monomeric titanyl complexes titanium(IV) binds strongly to a doubly bound oxo group at ca. 1.64 Å, to four ligands in the equatorial plane almost perpendicular to the Ti=O bond at ca. 2.02 Å, and there is one weakly bound ligand, trans to the Ti=O bond, at ca. 2.22 Å, for oxygen donor ligands; the O=Ti–O eq bond angles are 95°–100°. The structure of the DMSO solvated titanyl(IV) ion in the solid state is maintained in DMSO solution.

The coordination chemistry of d10 s2 metal ions is strongly affected by an (at least partially) occupied d10 s2 metal ion-ligand atom antibonding orbital, which may cause a void in the coordination sphere due to repulsion between the electrons in the antibonding orbital on the metal ion and those on the ligands. The character of the formed d10 s2 metal ion-ligand atom bond plays an important role in the electron density in the antibonding orbital and thereby also in the coordination chemistry. The hydrated tin(II) ion, [Sn(H2 O)3 ]2+ , and the trihydroxidostannate ion, [Sn(OH)3 ]- , have very different mean Sn-O bond lengths (2.21 and 2.08 Å, respectively) and O-Sn-O angles (ca. 78 and 90°, respectively) both in the solid state and in solution. On increasing the covalency of the tin(II)-ligand bonds, the repulsion decreases and higher coordination numbers are obtained, as seen in the dimethylsulfoxide- and N,N-dimethylthioformamide-solvated tin(II) ions, both of which are five-coordinate with square-pyramidal structures.

Densities and sound velocities at temperatures (298.15, 303.15, 308.15, 313.15 and 318.15) K of magnesium( II), calcium(II) and strontium(II) trifluoromethanesulfonates (triflates), as well as barium(II) perchlorate in N,N-dimethylformamide (dmf) and N,N-dimethylacetamide (dma) have been measured over the composition range studied. From these results, apparent molar volumes and apparent molar isentropic compressibilities at infinite dilution, as well as expansibilities have been evaluated. The results have been discussed in terms of ion-solvent interactions and coordination number. (C) 2015 Elsevier Ltd. All rights reserved.

A fundamental property of ions is their size, a known fact since before the acceptance of the modern atom model. The common way to describe the size of an ion is to determine its radius, defined as one of a pair of radii adding up to the bond distance between the centers of two nuclei. There are numerous factors that influence the ionic radius of a metal ion, where both valence and coordination number are essential when explaining reactivity, complexation, and chemical behavior. The similarity in ionic radii and chemical behavior between the elements in the lanthanoid and actinoid series is well-known and frequently used, making members of the former safe substitutes to avoid hazardous experiments with the radioactive actinoids. This review establishes reliable ionic radii for the nine-coordinate actinoid(III) ions, based on reported structural data, shedding light upon common misconceptions and clarifying the relationship between the ionic radii in the lantanoid and actinoid series. (C) 2016 Elsevier B.V. All rights reserved.

Biochars are known to affect the environmental fate of pesticides when used as soil amendments and have been suggested to be useful as cheap adsorbents of organic contaminants. We studied the ability of a wood-based biochar produced by slow pyrolysis from a mixture of about 80 % hardwood (Betula sp.) and 20 % softwood (Picea abies) to adsorb pesticides in order to assess its potential use as a filter material to prevent point source pollution in agriculture. The pesticides bentazone, chlorpyrifos, diuron, glyphosate and (4-chloro-2-methylphenoxy)acetic acid (MCPA) were used as model compounds. Their adsorption and desorption to the biochar were tested before and after it had been subjected to treatments with heat and/or iron intended to enhance its adsorptive properties. The adsorption affinity of the native biochar, as indicated by the Freundlich K F value, varied greatly and decreased in the order diuron > chlorpyrifos > MCPA > bentazone > glyphosate. Activation with heat (t = 450 °C) increased the specific surface area and the wettability of the biochar, measured by a water drop penetration time assay, and increased the adsorption of bentazone and MCPA. Treatment with iron salts, which partially coated the biochar with an iron oxide identified as magnetite, decreased the specific surface area but increased the adsorption of glyphosate. Mixing biochar fractions subjected to different treatments was a successful approach for optimising the adsorption of all model compounds and could be a viable path for creating a versatile yet comparably cheap filter material.

A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and binding forms, P adsorption capacity of discrete sediment layers, and pore water P concentrations. Lanthanum phosphate mineral phases were confirmed by solid state 31P MAS NMR and LIII EXAFS spectroscopy. Rhabdophane (LaPO4 · nH2O) was the major phase although indications of monazite (LaPO4) formation were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the theoretical aerial load indicated translocation of the LMB towards the deepest areas of the lakes. Lanthanum was generally recovered from bed sediment samples following sequential chemical extraction from the HCl fraction. Soluble reactive P (SRP) release experiments on intact sediment cores indicated conditions of P retention (with the exception of two lakes) by sediments, indicating effective control of sediment P release, i.e. between two and nine years after treatment.

Separation of trivalent actinoid (An(iii)) and lanthanoid (Ln(iii)) ions is extremely challenging due to their similar ionic radii and chemical properties. Poly-aromatic nitrogen compounds acting as tetradentate chelating ligands to the metal ions in the extraction, have the ability to sufficiently separate An(iii) from Ln(iii). One of these compounds, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzol[1,2,4]triazin-3-yl)[2,2]bipyridine, CyMe4-BTBP, has proven to be resistant towards acidic environments and strong radiation from radioactive decomposition. EXAFS studies of the dicomplexes of CyMe4-BTBP with americium(iii) and europium(iii) in nitrobenzene, cyclohexanone, 1-hexanol, 1-octanol and malonamide (DMDOHEMA) in 1-octanol have been carried out to get a deeper understanding of the parameters responsible for the separation. The predominating complexes independent of solvent used are [Am(CyMe4-BTBP)2(NO3)](2+) and [Eu(CyMe4-BTBP)2](3+), respectively, which are present as outer-sphere ion-pairs with nitrate ions in the studied solvents with low relative permittivity. The presence of a nitrate ion in the first coordination sphere of the americium(iii) complex compensates the charge density of the complex considerably in comparison when only outer-sphere ion-pairs are formed as for the [Eu(CyMe4-BTBP)2](3+) complex. The stability and solubility of a complex in a solvent with low relative permittivity increase with decreasing charge density. The [Am(CyMe4-BTBP)2(NO3)](2+) complex will therefore be increasingly soluble and stabilized over the [Eu(CyMe4-BTBP)2](3+) complex in solvents with decreasing relative permittivity of the solvent. The separation of americium(iii) from europium(iii) with CyMe4-BTBP as extraction agent will increase with decreasing relative permittivity of the solvent, and thereby also with decreasing solubility of CyMe4-BTBP. The choice of solvent is therefore a balance of a high separation factor and sufficient solubility of the CyMe4-BTBP ligand.

A laboratory scale experiment was set up to test the effect of dissolved organic carbon (DOC) as well as ageing of the La-P complex formed during phosphorus (P) sequestration by a La modified clay (Phoslock(®)). Short term (7 days) P adsorption studies revealed a significant negative effect of added DOC on the P sequestration of Phoslock(®), whereas a long-term P adsorption experiment revealed that the negative effect of added DOC was reduced with time. The reduced P binding efficiency is kinetic, as evident from solid-state (31)P magic-angle spinning (MAS) NMR spectroscopy, who showed that the P binding did not change in the presence of DOC. (31)P MAS NMR also reveals that up to 26% of the sequestered phosphate is as loosely bound redox-sensitive P species on the surface of rhabdophane (LaPO4 · nH2O, n ≤ 3). The ratio between the loosely bound P and lanthanum phosphate did not change with time, however both NMR and La LIII-extended x-ray absorption fine structure (EXAFS) spectroscopy shows a transformation of lanthanum phosphate from the initially formed rhabdophane towards the more stable monazite (LaPO4). Furthermore, the effect of natural DOC on the P binding capacity was tested using water and pore water from 16 Danish lakes. Whilst DOC has an immediate negative impact on P binding in the lake water, with time this effect is reduced.

The structure of the title compound, [Al 2 (OH) 2 (C 6 H 12 N 2 O) 6 ]I 4 ·4C 6 H 12 N 2 O (systematic name: di-μ 2 -hydroxido-bis{tris[1,3-dimethyltetrahydropyrimidin-2(1 H )-one-κ O ]aluminium} tetraiodide 1,3-dimethyltetrahydropyrimidin-2(1 H )-one tetrasolvate), is composed of two Al(C 6 H 12 N 2 O) 3 moieties linked into a centrosymmetric dinuclear unit by a pair of bridging hydroxide ions. The aluminium cations show a distorted trigonal bipyramidal AlO 5 coordination environment formed only by monodentate ligands. The Al—O bond lengths are in the range 1.789 (2)–1.859 (2) Å (mean bond length = 1.818 Å). The non-coordinating iodide anions compensate the charge of the complex cation. The remaining solvent molecules and the iodide counter-anions interact with the complex cation by weak non-classical C—H...I and C—H...O hydrogen bonds.