A 31P CP/MAS NMR study of PbS surface O,O'-dialkyldithiophosphate lead(II) complexes

31P CP/MAS NMR spectroscopy was used to study the adsorption of six different O,O'-dialkyldithiophosphate ions on the surface of synthetic galena (PbS). The 31P CP/MAS NMR spectra of the surface lead(II) dithiophosphates were compared with the 31P CP/MAS NMR spectra of polycrystalline lead(II) dithiophosphate complexes of the same ligands. Surface complexation of the dialkyldithiophosphate ions was established on the surface of PbS. A terminal S,S(')-chelating coordination is suggested for the surface complexes. The bulkier alkyl groups lead to surface precipitation in addition to the surface adsorption. Derivatives of monothiophosphoric and phosphoric acids were displayed as hydrolysis products of dialkyldithiophosphates on the synthetic PbS, the amount of which depends on the type of alkyl group.     

Characterization of active phosphorus surface sites at synthetic carbonate-free fluorapatite using single-pulse 1H, 31P, and 31P CP MAS NMR

The chemically active phosphorus surface sites defined as PO(x), PO(x)H, and PO(x)H2, where x = 1, 2, or 3, and the bulk phosphorus groups of PO4(3-) at synthetic carbonate-free fluorapatite (Ca5(PO4)3F) have been studied by means of single-pulse 1H,31P, and 31P CP MAS NMR. The changes in composition and relative amounts of each surface species are evaluated as a function of pH. By combining spectra from single-pulse 1H and 31P MAS NMR and data from 31P CP MAS NMR experiments at varying contact times in the range 0.2-3.0 ms, it has been possible to distinguish between resonance lines in the NMR spectra originating from active surface sites and bulk phosphorus groups and also to assign the peaks in the NMR spectra to the specific phosphorus species. In the 31P CP MAS NMR experiments, the spinning frequency was set to 4.2 kHz; in the single-pulse 1H MAS NMR experiments, the spinning frequency was 10 kHz. The 31P CP MAS NMR spectrum of fluorapatite at pH 5.9 showed one dominating resonance line at 2.9 ppm assigned to originate from PO4(3-) groups and two weaker shoulder peaks at 5.4 and 0.8 ppm which were assigned to the unprotonated PO(x) (PO, PO2-, and PO3(2-)) and protonated PO(x)H (PO2H and PO3H-) surface sites. At pH 12.7, the intensity of the peak representing unprotonated PO(x) surface sites has increased 1.7% relative to the bulk peak, while the intensity of the peaks of the protonated species PO(x)H have decreased 1.4% relative to the bulk peak. At pH 3.5, a resonance peak at -4.5 ppm has appeared in the 31P CP MAS NMR spectrum assigned to the surface species PO(x)H2 (PO3H2). The results from the 1H MAS and 31P CP MAS NMR measurements indicated that H+, OH-, and physisorbed H2O at the surface were released during the drying process at 200 degrees C.     

X-Ray and 31P CP MAS NMR studies of bis(dialkoxythiophosphoryl) disulfides

The crystal and molecular structures of the title compounds were determined by X-ray diffraction technique from diffractometer intensity measurements. It has been found that two homologous disulfides, bis(dimethoxythiophosphoryl) disulfide 1 and bis(dineopentoxythiophosphoryl) disulfide 2 , form different molecular and crystal structures with space groups C2/c and P&1macr;, respectively. These results were confirmed by ³¹P CP MAS NMR studies, which showed that under favorable conditions the solid state NMR may lead to determination of the number of crystallographically unique phosphorus atoms. Moreover, the variation of the disulfide S–S bond length versus torsional P–S–S–P angles was observed.     

Study of potassium O,O'-Dibutyldithiophosphate combining DFT, 31P CP/MAS NMR and infrared spectroscopy

Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O, O'-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and (31)P CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and (31)P NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or (31)P chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them.     

Structural organization of the tetranuclear zinc di-iso-propyl phosphorodithioate complex [Zn4O{S2P(O-iso-C3H7))2}6] as probed by single-crystal x-ray diffraction and 13C and 31P CP/MAS NMR

The zinc O,O’-di-iso-propyl phosphorodithioate complex [Zn₄O?ub;S₂P(O-iso-C₃H₇)₂?ub;₆] (I) has been synthesized and characterized by multinuclear MAS NMR (¹³C, ³¹P). The metal core of the tetranuclear structure of I, determined by single-crystal X-ray diffraction, is a tetrahedron centered by an oxygen atom. All Dtph ligands are structurally nonequivalent and act as μ₂ bridges combining pairs of zinc atoms. Bonding of all metal atoms to the μ₄ oxygen atom provides additional stabilization of the structure. For ³¹P NMR signals, the chemical shift anisotropy δ_aniso and the asymmetry parameter η were calculated, which allowed to assign them to the phosphorus positions in the structure of I.     

Adducts of zinc and copper(II) dimethyland diethyldithiocarbamates with piperidine: Synthesis, EPR, solid-state natural abundance 13C and 15N CP/MAS NMR and single-crystal X-ray diffraction studies

Crystalline adducts of zinc and copper(II) dimethyl-and diethyldithiocarbamates with piperidine (Pip) of the general formula [M{NH(CH₂)₅}(S₂CNR₂)₂] (M = Zn and ⁶³Cu; R = CH₃ and C₂H₅) were obtained. Their structures and spectroscopic characteristics were studied by X-ray diffraction analysis, EPR spectroscopy, and solid-state natural abundance ¹³C and ¹⁵N MAS NMR spectroscopy. The most substantial differences between the adducts of the formula [Zn{NH(CH₂)₅}(S₂CNR₂)₂] (R = CH₃ and C₂H₅) were found in the spatial orientations of the coordinated heterocycles and the geometries of the zinc polyhedra. The individual character of the EPR spectra of magnetically diluted isotope-substituted copper(II) adducts was determined by computerassisted modeling. The adducts of copper(II) and zinc dimethyldithiocarbamates proved to exist as two isomers. The coordination polyhedra of copper(II) and zinc are intermediate between a tetragonal pyramid (TP) and a trigonal bipyramid (TBP). The contributions from the TBP/TP components to the coordination polyhedra were quantitatively estimated from X-ray diffraction data. The ¹³C and ¹⁵N NMR signals were assigned to the positions of the atoms of the =NC(S)S^? groups in the resolved (according to X-ray diffraction data) molecular structures of the adducts.     

Multinuclear (11B, 31P) MAS NMR spectroscopy of borophosphates

¹¹B and ³¹P MAS NMR spectroscopy of three borophosphates was used to monitor their phase composition via the isotropic chemical shifts. CaBPO₅ and BPO₄ represent nearly pure samples, SrBPO₅ contains β-Sr₂P₂O₇ as well as BPO₄ as impurities. The anisotropic chemical shift data provide additional information on the geometry and connectivity of the BO₄ and PO₄ building units. Received: 25 July 1996 / Revised: 19 August 1996 / Accepted: 23 August 1996     

Multinuclear (11B, 31P) MAS NMR spectroscopy of borophosphates

¹¹B and ³¹P MAS NMR spectroscopy of three borophosphates was used to monitor their phase composition via the isotropic chemical shifts. CaBPO₅ and BPO₄ represent nearly pure samples, SrBPO₅ contains β-Sr₂P₂O₇ as well as BPO₄ as impurities. The anisotropic chemical shift data provide additional information on the geometry and connectivity of the BO₄ and PO₄ building units. Received: 25 July 1996 / Revised: 19 August 1996 / Accepted: 23 August 1996     

C CP MAS NMR, FTIR, X-ray diffraction and PM3 studies of some N-(ω-carboxyalkyl)morpholine hydrohalides

N-(ω-carboxyalkyl)morpholine hydrochlorides, OC₄H₈N(CH₂)_nCOOH·HCl, n=1–5, were obtained and analyzed by ¹³C cross polarization (CP) magic angle spinning (MAS) NMR, FTIR and PM3 calculations. The structure of N-(3-carboxypropyl)morpholine hydrochloride (n=3) has been solved by X-ray diffraction method at 100 K and refined to the R=0.031. The crystals are monoclinic, space group P2₁/c, a=14.307(3), b=9.879(2), c=7.166(1) Å, β=93.20(3)°, V=1011.3(3) ų, Z=4. In this compound the nitrogen atom is protonated and two molecules form a centrosymmetric dimer, connected by two N⁺–HCl⁻ (3.095(1) Å) and two O–HCl⁻ (3.003(1) Å) hydrogen bonds. ¹³C CP MAS NMR spectra, contrary to the solution, showed non-equivalence of the ring carbon atoms. The PM3 calculations predict a molecular dimer without proton transfer for an HCl complex, while for an HBr complex an ion pairs with proton transfer, and reproduces correctly the conformation of both dimers but overestimates H-bond distances. Shielding constants calculated from the PM3 geometry of ion pairs gave a linear correlation with the ¹³C chemical shifts in solids.     

X-ray, 31P CP/MAS,and single-crystal NMR studies,and 31P DFT GIAO calculations of inclusion complexes of bis[6-O,6-O'-(1,2:3,4- diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] disulfide: the importance of C-H...S=P contacts in the solid state

Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl) thiophosphoryl] disulfide shows a strong tendency to form inclusion compounds. The crystal and molecular structure of eight different solvates was established by X-ray analysis. The results indicate three different types of disulfide arrangements in the crystal lattice. By means of 31P CP/MAS NMR experiments the principal values delta 11, delta 22, and delta 33 of the 31P chemical shift tensor were obtained for each form. The orientation of its principal axes with respect to a molecular frame was investigated by means of 31P CP and single-crystal NMR for the complex with propan-2-ol. The principal axis 1 of both chemically equivalent phosphorus atoms is nearly parallel to the P-S bond and the principal axis 3 is very close to the P=S bond. DFT GIAO calculations of the model compound (EtO)2(S)P1SSP2(S)-(OEt)2 allowed assignment of the experimental chemical shift curves to the magnetically nonequivalent atoms P1 and P2. The maximum difference between calculated angles [symbol: see text] i-P-X)calcd and experimental angles [symbol: see text] i-P-X)exptl is 8.3 degrees and the rms distance 3.8 degrees (i = principal axes 1, 2, 3; X = S, -S-, -O1-, -O2-). The influence of C-H...S weak hydrogen bonding on phosphorus shielding was tested theoretically (31P DFT GIAO) employing the dimethoxythiophosphoryl disulfide.CH4 complex as a model compound. The sensitivity of 31P delta ii parameters to intermolecular forces is demonstrated.     

Characterization of Five-Coordinate Ruthenium(II) Phosphine Complexes by X-ray Diffraction and Solid-State (31)P CP/MAS NMR Studies and Their Reactivity with Sulfoxides and Thioethers

31P CP/MAS NMR spectroscopy is examined as a method of characterization for ruthenium(II) phosphine complexes in the solid state, and the results are compared with X-ray crystallographic data determined for RuCl(2)(dppb)(PPh(3)) (dppb = Ph(2)P(CH(2))(4)PPh(2)), RuBr(2)(PPh(3))(3), and the previously determined RuCl(2)(PPh(3))(3). Crystals of RuBr(2)(PPh(3))(3) (C(54)H(45)Br(2)P(3)Ru) are monoclinic, space group P2(1)/a, with a = 12.482(4) ?, b = 20.206(6) ?, c = 17.956(3) ?, beta = 90.40(2) degrees, and Z = 4, and those of RuCl(2)(dppb)(PPh(3)) (C(46)H(43)Cl(2)P(3)Ru) are also monoclinic, space group P2(1)/n, with a = 10.885(2) ?, b = 20.477(1) ?, c = 18.292(2) ?, beta = 99.979(9) degrees, and Z = 4. The structure of RuBr(2)(PPh(3))(3) was solved by direct methods, and that of RuCl(2)(dppb)(PPh(3)) was solved by the Patterson method. The structures were refined by full-matrix least-squares procedures to R = 0.048 and 0.031 (R(w) = 0.046 and 0.032) for 5069 and 5925 reflections with I >/= 3sigma(I), respectively. Synthetic routes to RuBr(2)(dppb)(PPh(3)) and [RuBr(dppb)](2)(&mgr;(2)-dppb) are reported. The reactivity of RuCl(2)(dppb)(PPh(3)) with the neutral two-electron donor ligands (L) dimethyl sulfoxide, tetramethylene sulfoxide, tetrahydrothiophene, and dimethyl sulfide to give [(L)(dppb)Ru(&mgr;-Cl)(3)RuCl(dppb)] is discussed.     

CP/MAS 13C NMR characterization of the isomeric states and intermolecular packing in tris(8-hydroxyquinoline) aluminum(III) (Alq3)

The isomeric states and intermolecular packing of tris(8-hydroxyquinoline) aluminum(III) (Alq(3)) in the alpha-, gamma-, and delta-crystalline forms and in the amorphous state, which are important for understanding the light-emitting and electron-transport properties, have been analyzed by CP/MAS (13)C NMR. This simple NMR experiment shows that the isomeric state of alpha- and amorphous Alq(3) is meridional, whereas that of gamma- and delta-Alq(3) is facial. In the amorphous Alq(3), the inclusion of facial isomers has been under debate. Our experiments show that meridional isomers are dominant in the amorphous Alq(3), although the existence of facial isomers cannot be completely denied. The local structure of amorphous Alq(3) is similar to that of alpha-Alq(3) and is significantly different from those of gamma- and delta-Alq(3). Among these Alq(3) samples, the effect of intermolecular interaction is not found only for gamma-Alq(3). This finding can explain the good solvent solubility of gamma-Alq(3), compared with the other crystalline forms. It is also shown that the structures are locally disordered not only for amorphous Alq(3) but also for alpha-Alq(3), although clear X-ray diffraction peaks are observed for alpha-Alq(3). In contrast, the local structures of gamma- and delta-Alq(3) are well defined. A clear relation is found between the spectral patterns of CP/MAS (13)C NMR and the fluorescence wavelengths; the samples, which consist of facial isomers, show blue-shifted fluorescence compared with those of meridionals.     

Tetraphenyl-and tetratolylantimony complexes with N,N-dialkyldithiocarbamate ligands: Synthesis, X-ray diffraction analysis, and 13C and 15N CP/MAS NMR studies

Crystalline tetraphenylantimony and tetratolylantimony complexes with N,N-dialkyldithiocarbamate ligands [Sb(C₆H₅)₄(S₂CNR₂)] (R = CH₃, C₂H₅, and C₃H₇ and R₂ = (CH₂)₆) were synthesized by ligand exchange reactions and studied by ¹³C and ¹⁵N CP/MAS NMR spectroscopy. X-ray diffraction analysis revealed that the complex [Sb(n-CH₃-C₆H₄)₄{S₂CN(C₃H₇)₂}] exists as the single molecular form, while [Sb(C₆H₅)₄{S₂CN(CH₂)₆}] exists as two molecular conformers. The ¹³C and ¹⁵N signals were assigned to the positions of the atoms in the isomeric structures [Sb(C₆H₅)₄{S₂CN(CH₂)₆}] in terms of different degrees of double bonding in the formally single =N-C(S)S-bond.     

Correlations between 31P chemical shift anisotropy and molecular structure in polycrystalline O,O'-dialkyldithiophosphate zinc(II) and nickel(II) complexes: 31P CP/MAS NMR and ab initio quantum mechanical calculation studies

Different potassium salts and zinc(II) and nickel(II) O,O'-dialkyldithiophosphate complexes were studied by solid-state 31P CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the 31P chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew kappa, while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the delta22 component of the 31P chemical shift tensor and the S-P-S bond angle in the O,O'-dialkyldithiophoshate zinc(II) and nickel(II) complexes was found: delta22 increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100 degrees to 120 degrees , while the other two principal values of the tensor, delta11 and delta33, are almost conserved. This eventually leads to the change in sign for kappa in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-dialkyldithiophosphate group forming chelating four-membered P(ss)Me heterocycles.     

Piperazinium dihydrogen phosphate,C4H12N2(H2PO4)2: Synthesis, 31P CP/MAS NMR,structural and thermal investigations

A new piperazinium dihydrogen orthophosphate, C₄H₁₂N₂(H₂PO₄)₂ was discovered and characterized by combining information from X-ray diffraction, ³¹P CP/MAS NMR and thermal analysis (TG/DTA). The compound C₄H₁₂N₂(HPO₄)·H₂O, was also studied in order to compare these two similar materials. The hydrothermal stability is investigated for the system: 1.0 C₄H₁₀N₂: n H₃PO₄: 55–60 H₂O, 0.5 < n < 3. The reaction mixtures with pH in the range 1.6–8.4 were placed at a fixed temperature in the range 20–180 °C for ca. 5 days. C₄H₁₂N₂(H₂PO₄)₂ was obtained when n > ca. 2. A crystal of piperazinium dihydrogen phosphate, C₄H₁₂N₂(H₂PO₄)₂ was structurally investigated using X-ray diffraction: triclinic, space group $P\overline{1}$, a = 7.023(2), b = 7.750(3), c = 12.203(4) Å, α = 84.668(7), β = 81.532(7) and γ = 63.174(6)°, V = 586.0(4) Å³ and Z = 2. The reactivity of C₄H₁₂N₂(H₂PO₄)₂ was investigated by systematic solvothermal syntheses.     

Synthesis,characterization and reactivity of a neutral antimony(III) complex

Pincer complexes are widely used in organometallic and coordination chemistry. The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years. Although phenylenediamine derived PXP (X = B, Al, C, Si, Ge, Sn, N) type ligands exhibit diverse reactivity, analogues species based on antimony have been reported less frequently. Herein, we report a new PSbP complex and evaluate its reactivity. These species will broaden the family of phenylenediamine derived pincer complexes.