Anna-Carin Larsson

Polycrystalline and surface O,O′-dialkyldithiophosphate zinc(II) complexes : preparation, 31P CP/MAS NMR and single-crystal X-ray diffraction studies

Abstract Dithiophosphate zinc(II) complexes with eight different O , O ′-dialkyldithiophosphate ligands have been prepared in solid/liquid states and as surface complexes on a synthetic sphalerite, and studied by means of 31 P NMR spectroscopy. All 31 P resonances, corresponding to dithiophosphate ligands with different structural functions (i.e. terminal chelating or bridging between two metal atoms in bi- and tetranuclear complexes), have been assigned on the basis of comparative analyses of chemical shift data for solid complexes, their melts and chloroform solutions at various concentrations. The bridging coordination of O , O ′-dialkyldithiophosphate ligands by the two neighbouring zinc(II) atoms was established in the case of zinc(II) complexes formed at the surface of the synthetic sphalerite. In addition, novel molecular and crystal structures of the binuclear O , O ′-di- cyclo -hexyldithiophosphate zinc(II) complex have been resolved by single-crystal X-ray diffraction data analysis, and useful correlations with 31 P NMR data for this complex were obtained.

Surface complexation modeling of inositol hexaphosphate sorption onto gibbsite.

The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, (31)P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. (31)P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, -6, -13 and -21ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and (31)P MAS NMR data, IP6 sorption to gibbsite was modeled with an extended constant capacitance model (ECCM). The adsorption reactions that best described the sorption of IP6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex: ≡AlOH + IP₆¹²⁻ + 5H⁺ ↔ ≡Al(IP₆H₄)⁷⁻ + H₂O, ≡3AlOH + IP₆¹²⁻ + 6H⁺ ↔ ≡Al₃(IP₆H₃)⁶⁻ + 3H₂O, ≡2AlOH + IP₆¹²⁻ + 4H⁺ ↔ (≡AlOH₂)₂²⁺(IP₆H₂)¹⁰⁻. The inner-sphere complex involving three surface sites may be considered to be equivalent to a surface precipitate. Thermodynamic parameters were obtained from equilibrium constants derived from surface complexation modeling. Enthalpies for the formation of inner-sphere surface complexes were endothermic, while the enthalpy for the outer-sphere complex was exothermic. The entropies for the proposed sorption reactions were large and positive suggesting that changes in solvation of species play a major role in driving the sorption process.

Study on Potassium iso-Propylxanthate and Its Decomposition Products: Experimental 13C CP/MAS NMR Combined with DFT Calculations

Solid-state (13)C NMR is believed to be a valuable tool for studying adsorption and speciation of xanthates on sulfide mineral surfaces, but to do that, model compounds of possible xanthate species need to be investigated. (13)C NMR chemical shift tensors for molecular fragments of potassium iso-propylxanthate and six of its decomposition products have been determined by combining DFT calculations and (13)C CP/MAS NMR experiments. DFT calculations were performed in NWChem using GIAO method for the NMR shielding tensor calculations. The results of the calculations are in good agreement with experimental data. In the -XCYZ moiety (X, Y, Z = O, S), the more sulfur atoms, the more deshielded the chemical shift becomes and the larger the span of the chemical shift tensor. The δ11 principal value has the largest influence on the span, decreasing when the number of sulfur atoms decreases and the number of oxygen atoms increases. The significant differences in chemical shifts make it possible to distinguish between different species and, hence, in future studies, interpret surface speciation. The tensor parameters can also aid in the interpretation.

The effect of inositol hexaphosphate on cadmium sorption to gibbsite.

HYPOTHESIS Oxides, hydrous oxides and hydroxides of aluminium and iron are important in determining the availability of trace and heavy metals in soil systems. The presence of complexing anions is also known to affect the binding of these metals in soils. Since organophosphates, such as inositol hexaphosphate (IP6), are present in most soil systems they are expected to affect the nature of the interaction between metal ions and metal (hyr)oxides. EXPERIMENTS Both adsorption edge and isotherm experiments were conducted on Cd(II)-gibbsite and Cd(II)-IP6-gibbsite systems. In addition, solid-state (31)P MAS NMR measurements were performed on the ternary system. All results were used to develop Extended Constant Capacitance surface complexation models of both the Cd(II)-gibbsite and IP6-Cd(II)-gibbsite sorption systems. FINDINGS The presence of IP6 significantly increased sorption of Cd(II) to gibbsite below pH 8 especially at higher concentrations of Cd(II) and IP6. The (31)P MAS NMR spectra, together with surface complexation modeling, indicated the presence of two outer-sphere ternary complexes with the first, [(SOH2)3(3+)(LHCd)(9-)](6-), important at relatively low concentrations, while the second, [SLH3(8-)Cd(2+)](6-), dominated sorption at higher sorbate concentrations. Thus the presence of organophosphates in soil systems increases sorption and may therefore decrease the availability of trace and heavy metals to plants.

Polymeric thallium(I) O,O′-diisopropyl dithiophosphate [Tl{S2P(O-iso-C3H7)2}]n: Synthesis, structure, and 13C and 31P CP/MAS NMR spectra

The crystalline polymeric thallium(I) O,O′-diisopropyl dithiophosphate [Tl{S2P(O-iso-C3H7)2}]n (I) was obtained and examined by solid-state 13C and 31P CP/MAS NMR spectroscopy. Diagrams of the χ2 statistic were constructed from the complete 31P MAS NMR spectra and used to calculate the 31P chemical shift anisotropy (δaniso = (δzz − δiso)) and the asymmetry parameter (η = (δyy − δxx)/(δzz − δiso)). The 31P chemical shift tensor has a nearly axial symmetry (η = 0.22, δzz < δyy ≈ δxx). The MAS NMR spectral patterns correspond to the negative sign of δaniso (δzz < δyy < δxx), which indicates bridging or chelating-bridging coordination of the dithiophosphate ligands (Dtph). X-ray diffraction analysis revealed a polymeric structure of compound I. The polymer chain consists of alternating mononuclear [Tl{S2P(O-iso-C3H7)2}] molecules with opposite spatial orientations. The Dtph ligands are coordinated in a mixed, chelating-μ3-bridging fashion. The shape of the 31P NMR signal was interpreted in terms of the 31P-203,205Tl coupling pattern proposed from crystallographic data.

DFT calculations in the assignment of solid-state NMR and crystal structure elucidation of a lanthanum(III) complex with dithiocarbamate and phenanthroline

The molecular, crystal, and electronic structures as well as spectroscopic properties of a mononuclear heteroleptic lanthanum(iii) complex with diethyldithiocarbamate and 1,10-phenanthroline ligands (3 : 1) were studied by solid-state 13C and 15N cross-polarisation (CP) magic-angle-spinning (MAS) NMR, X-ray diffraction (XRD), and first principles density functional theory (DFT) calculations. A substantially different powder XRD pattern and 13C and 15N CP-MAS NMR spectra indicated that the title compound is not isostructural to the previously reported analogous rare earth complexes with the space group P21/n. Both 13C and 15N CP-MAS NMR revealed the presence of six structurally different dithiocarbamate groups in the asymmetric unit cell, implying a non-centrosymmetric packing arrangement of molecules. This was supported by single-crystal X-ray crystallography showing that the title compound crystallised in the triclinic space group P1[combining macron]. In addition, the crystal structure also revealed that one of the dithiocarbamate ligands has a conformational disorder. NMR chemical shift calculations employing the periodic gauge including projector augmented wave (GIPAW) approach supported the assignment of the experimental 13C and 15N NMR spectra. However, the best correspondences were obtained with the structure where the atomic positions in the X-ray unit cell were optimised at the DFT level. The roles of the scalar and spin-orbit relativistic effects on NMR shielding were investigated using the zeroth-order regular approximation (ZORA) method with the outcome that already the scalar relativistic level qualitatively reproduces the experimental chemical shifts. The electronic properties of the complex were evaluated based on the results of the natural bond orbital (NBO) and topology of the electron density analyses. Overall, we apply a multidisciplinary approach acquiring comprehensive information about the solid-state structure and the metal-ligand bonding of the heteroleptic lanthanum complex.

Crystalline nickel(II) di-i-amyl dithiophosphate, [Ni{S2P(O-i-C5H11)2}2]: Preparation, structure, heteronuclear (13C, 31P) CP/MAS NMR spectra, and thermal behavior

The crystalline nickel(II) di-i-amyl) dithiophosphate (Dtph), [Ni{S2P(O-i-C5H11)2}2] (I) was isolated on a preparative scale and characterized by 13C, 31P MAS NMR, and X-ray diffraction (CIF file CCDC no. 1469369). The χ2-statistic diagrams were constructed from full 31P CP/MAS NMR spectra for calculating the 31P chemical shift anisotropy: δaniso = δzz–δiso and the asymmetry parameter η = (δyy–δxx)/(δzz–δiso). The key structural unit of I is the centrosymmetric [Ni{S2P(O-i-C5H11)2}2] molecule in which the nickel atom coordinates two Dtph ligands in the isobidentate fashion. In molecule I, each carbon, oxygen, and sulfur atom is statistically disordered over two sites with equal occupancies. However, the disorder does not affect nickel and phosphorus. These results were interpreted as the presence in I of two [Ni{S2P(O-i-C5H11)2}2] molecules rotated through 21.0(1)° (the angle between the [NiS4] chromophore planes) relative to each other around the bisecting P–Ni–P axis passing through both four-membered [NiS2P] rings. The two molecules occupy crystal lattice sites with equal probabilities. The thermal behavior of I was studied by simultaneous thermal analysis under argon. The course of the thermal destruction of the complex was established, nickel pyrophosphate (Ni2P2O7) was identified as the final product of thermal transformations.

Polymeric gold(I) diisobutyl dithiophosphate, [Au2{S2P(O-iso-C4H9)2}2]n: Synthesis, supramolecular self-organization (a role of aurophilic interaction), 13C and 31P MAS NMR spectroscopy, and thermal behavior

A new polymeric gold(I) diisobutyl dithiophosphate (Dtph), [Au2{S2P(O-iso-C4H9)2}2]n (I), was preparatively obtained and characterized by 13C and 31P MAS NMR spectroscopy and X-ray diffraction (CIF file CCDC no. 977818). Diagrams of the χ2 statistic were constructed from the complete 31P MAS NMR spectra and used to calculate the 31P chemical shift anisotropy (δaniso = δzz − δiso) and the asymmetry parameter η = (δyy − δxx)/(δzz − δiso). The main structural unit of complex I is the noncentrosymmetric dinuclear molecule [Au2{S2P(O-iso-C4H9)2}2], in which the gold atoms are linked by two bridging ligands Dtph. The central cyclic structural fragment of the dimer [Au2S4P2] is additionally stabilized by the intramolecular aurophilic interaction Au⋯Au. Further supramolecular self-organization of the complex involves intermolecular aurophilic bonds Au⋯Au that serve to unite adjacent dinuclear molecules [Au2{S2P(O-iso-C4H9)2}2] with different spatial orientations into the polymer chains ([Au2{S2P(O-iso-C4H9)2}2])n. The thermal behavior of complex I was examined by synchronous thermal analysis under argon. The character of the thermolysis of the complex to reduced metallic gold as a final product was determined.

Binding of Au3+ from solutions by nickel(II) and cadmium diisopropyl dithiophosphates: MAS 31P NMR, structure and thermal behavior of the polynuclear complex [Au2{S2P(O-iso-C3H7)2}2] n

The paper deals with reactions of freshly precipitated diisopropyl dithiophosphate (Dtph) complexes of nickel(II), [Ni{S2P(O-iso-C3H7)2}2] and cadmium, [Cd2{S2P(O-iso-C3H7)2}4], with the [AuCl4]− in 2M HCl, resulting in gold transition from the solution to the precipitate as polymeric gold(I) diisopropyl dithiophosphate. The reduction of gold(III) to gold(I) noted in both cases is due to oxidation of the relevant part of the Dtph group to bis(O,O′-di-(iso)-propoxythiophosphoryl) disulfide, (iso-C3H7O)2P(S)S-S(S)P(O-iso-C3H7)2. The polynuclear gold(I) complex [Au2{S2P(O-iso-C3H7)2}2]n (I) was isolated on a preparative scale from the chemisorption system and studied by MAS 31P NMR and X-ray diffraction. The key structural unit of I is the non-centrosymmetric binuclear molecule [Au2{S2P(O-iso-C3H7)2}2] in which the gold atoms are connected by two bridging Dtph groups. The structure contains two types of non-equivalent binuclear molecules related as conformational isomers. Owing to the relatively weak Au-Au contacts, the neighboring binuclear [Au2{S2P(O-iso-C3H7)2}2] molecules are involved in an infinite polymeric chain with conformer alternation along the chain. To elucidate the conditions for the recovery of bound gold(I), the precipitates formed in the sorption systems were studied by simultaneous thermal analysis under argon. As the final product, thermolysis gives reduced metallic gold. The ability of dithiophosphate complexes to bind gold from a solution is much lower than that of dithiocarbamate complexes, which is due to oxidation of some Dtph groups to disulfide.

The diethyl dithiophosphate complex of tetraphenylantimony(V) and its solvated form, [Sb(C6H5)4{S2P(OC2H5)2}] · 1/2 C6H6: Synthesis, crystal structure, and 13C, 31P CP/MAS NMR study. an example of monodentate coordination of dithio ligands

The O,O′-diethyl dithiophosphate complex of tetraphenylantimony(V) [Sb(C6H5)4{S2P(OC2H5)2}] (I) and its benzene-solvated form I · 1/2C6H6 (II) were synthesized and studied by high-resolution solid-state 13C and 31P NMR (MAS NMR). The diethyl dithiophosphate (Dtph) groups in I and II were quantitatively characterized by the 31P chemical shift anisotropy (δaniso), the asymmetry parameter (η), and the principal values of chemical shift tensors (δxx, δyy, δzz). The calculation of the anisotropy parameters included construction of χ2 statistic diagrams from full 31P MAS NMR spectra. In both complexes, the Dtph groups were found to have mainly axially symmetric 31P chemical shift tensors (for δzz < δxx ≈ δyy) with similar anisotropy parameters (δaniso and η), which is due to their identical S-monodentate function. According to X-ray diffraction data, II has a trigonal bipyramidal (TBP) molecular structure with Smonodentate coordination of Dtph in the TBP axial position and outer-sphere position of the benzene molecule. The desorption of the outer-sphere benzene solvent molecules from structure II, which was noted in MAS NMR experiment, passes through the formation of three intermediate solvated forms with benzene content n < 1/2.