Solid-state 31P CPMAS NMR Research Articles

Conductivity behavior and solid state NMR investigation of imidazolium-based polymeric ionic liquids

Novel proton-conducting anhydrous polymer electrolytes comprising imidazolium ionic liquid units in the polymeric structure have been synthesized. These polymeric ionic liquid electrolytes were doped with phosphoric acid to get Poly(AcIm-n)xH 3PO 4, where x is the number of moles of H 3PO 4 per polymer repeat unit and n is the number of alkyl spacers (–CH 2). Thermogravimetric analysis (TGA) illustrates that these materials are thermally stable up to about 200 °C. DSC results show the softening effect of the length of the spacers as well as phosphoric acid. Mechanical studies displayed the cross-linking of the samples which were also confirmed by solid state 31P CPMAS NMR spectra. The proton conductivity of the samples increases with x and reaches 10 −2 S cm −1 at 120 °C for both Poly(AcIm-2)2H 3PO 4 and Poly(AcIm-6)2H 3PO 4. The conductivity isotherms show that the proton transport in acid-doped polymeric ionic liquids obeys VTF behavior.

Novel bicyclic hexanuclear copper(I) aggregate: Structure and solid state 31P CPMAS NMR spectra of [(Cu 3L 3) 2] and [Cu(PPh 3) 2L] complexes of N-(diisopropoxythiophosphinyl)- N′-phenylthiourea (HL)

A new complex of N-thiophosphorylthiourea PhNHC(S)NHP(S)(O iPr) 2 ( HL) of formula [(Cu 3L 3) 2] has been synthesized and characterized by single crystal X-ray diffraction, FT-IR, 1H, 31P NMR in solution and by 31P CPMAS NMR spectroscopy in the solid state. A comparison of the structure and the spectral parameters of [(Cu 3L 3) 2] with those of the mononuclear analogue [Cu(PPh 3) 2L] was performed. In the solid state the aggregate [(Cu 3L 3) 2] represents the first example of a spontaneous “side-by-side” association of two neutral cyclic [Cu 3L 3] moieties using two Cu–S–Cu bridges formed by the sulfur atoms of the PS-groups. The values of the 1 J( 31P– 63,65Cu) and 2 J( 31P– 31P) coupling constants of the [Cu(PPh 3) 2] + moiety in the solid state spectra are reported.

Syntheses, molecular structures and pH-dependent monomer–dimer equilibria of Dawson α2-monotitanium(iv)-substituted polyoxometalates

The preparation and structural characterization of a novel, solid Brønsted acid based on Dawson alpha2-monotitanium(IV)-substituted polyoxometalates (POMs) are described. The free-acid form of the POM, i.e., 13H+-heteropolyacid with the formula H13[1b].55H2O DH-1 (1b = [(alpha2-P2W17TiO61)(alpha2-P2W17TiO61H)(mu-O)]13-), was prepared by passing an aqueous solution containing a potassium salt precursor, K14[1a].17H2O DK-1 (1a=[(alpha2-P2W17TiO61)2(mu-O)]14-), through a cation-exchange resin column. Compound DK-1 was obtained by a stoichiometric reaction of mono-lacunary Dawson POM [alpha2-P2W17O61]10- with Ti(SO4)2 in an aqueous solution. [Note: the abbreviations D, M, K and H stand for dimer, monomer, potassium salt and free-acid form, respectively.] Compounds DK-1 and DH-1 were characterized by using complete elemental analysis, thermogravimetric (TG) and differential thermal analysis (DTA), FTIR, solution (31P and 183W) NMR spectroscopy, pH-varied 31P NMR spectroscopy, solid-state 31P CPMAS NMR, X-ray crystallography and acidity measurements in an organic solvent with a Hammett indicator for DH-1. The monomeric form, K8[alpha2-P2W17TiO62]. 18H2O MK-1, was derived from DK-1. The molecular structure of 1b was composed of a dimer connected through one Ti-O-Ti bond between two alpha2-mono-Ti(IV)-substituted Dawson POM subunits. BVS (bond valence sum) calculation showed that one oxygen atom (O(60A)) in one of the two Dawson subunits was protonated, therefore the two subunits were unequivalent. On the other hand, the molecular structure of la was a Ti-O-Ti bonding dimer of two equivalent Dawson subunits. The pH-varied 31P NMR spectra of DK-1 and DH-1 in aqueous solutions showed that the monomer at pH 7.0, the dimer at pH 1.0-3.0, and the mono-protonated species of the dimer at pH 0.5 were the predominant species in the solutions. The Hammett acidity constant (H0) of DH-1 in CH3CN (-2.87) was estimated to be almost the same as that of homo-Dawson heteropolyacid H6[P2W18O62].17H2O(-2.77).

Formation of nanosized zirconia-supported 12-tungstophosphoric acid in mesoporous silica SBA-15: A stable and versatile solid acid catalyst for benzylation of phenol

A nanosized zirconia-supported 12-tungstophosphoric acid (TPA) in SBA-15 composite was prepared by wet impregnation of TPA/ZrO 2 nanoparticles inside the mesoporous channels of SBA-15. The resulting composite material was calcined at 1123 K and characterized by elemental analysis, powder X-ray diffraction, nitrogen adsorption isotherms, transmission electron microscopy (TEM), scanning electron microscopy (SEM), solid-state 31P CP-MAS NMR, 29Si MAS NMR, UV–vis diffuse reflectance spectra, FTIR, TPD of ammonia, FTIR pyridine adsorption, and thermogravimetric analysis (TG-DTG). The synthesized TPA/ZrO 2/SBA-15 showed a well-ordered hexagonal mesoporous structure and mesoporous support SBA-15 stabilized ZrO 2-t (tetragonal) phase with crystal size in the range of 3–4 nm. SBA-15 was a better support than MCM-41 and MCM-48 because it retained its mesostructure even after high TPA loading and high calcination temperatures. Mesoporous silica support plays an important role in stabilizing the catalytically active tetragonal phase of zirconia, which gave the most active catalysts. The catalysts were examined for their catalytic activities in the liquid phase benzylation of phenol with benzyl alcohol and the catalyst 15 wt% TPA/22.4 wt% ZrO 2/SBA-15 calcined at 1123 K was found to have high acidity and to be 10 times more active than neat TPA/ZrO 2 under the reaction conditions studied in benzylation of phenol.

Structural and spectroscopic studies on three-coordinate complexes of copper(i) halides with tricyclohexylphosphine

Three-coordinate 1 ∶ 1 and 1 ∶ 2 compounds of copper(I) halides with tricyclohexylphosphine have been synthesised and characterized by single crystal X-ray structure determinations, 63Cu NQR spectroscopy, solid state 31P CPMAS NMR spectroscopy, and low frequency vibrational spectroscopy. The 1 ∶ 1 compounds crystallize as isomorphous, centrosymmetric [(PCy3)Cu(μ-X)2Cu(PCy3)] dimers with three-coordinate (PCuX2) copper. Solid state 31P CPMAS NMR spectra show asymmetric quartets with the spectra of the chloride and bromide compounds broadened by quadrupole relaxation effects. For X = I, 1J(31P–63Cu) is 1.74 kHz with the quadrupole distortion parameter, dνCu, 11.5 × 109 Hz2. Far infrared spectra of the compounds are unusually complex with groups of strong bands in the region expected for ν(CuX) vibrational modes (100–260 cm−1). The 1 ∶ 2 compounds crystallize as [CuX(PCy3)2] monomers. The solid state 31P NMR spectra of the bromide and iodide compounds show sharp asymmetric quartets with 1J(P–Cu) 1.20 and 1.23 kHz and dνCu 8.7 and 10.3 × 109 Hz2 respectively. Relaxation effects collapse the spectrum of the chloride to a broad doublet. Room temperature 63Cu NQR frequencies for [CuX(PCy3)2] are found to be 34.5, 33.43 and 32.06 MHz for X = Cl, Br and I respectively and are of the order of 4 MHz greater than values recorded for the 1 ∶ 1 complexes. Far infrared spectra of the complexes exhibit strong bands due to ν(CuX) vibrational modes at 253, 189 and 156 cm−1 for X = Cl, Br and I.

Structural and spectroscopic studies on three- and two-co-ordinate copper(I) halide tribenzylphosphine complexes

Three-co-ordinate, monomeric 1∶2 complexes of tribenzylphosphine (PBz3) with copper(I) halides, [Cu(PBz3)2X] (X = Cl, Br or I), have been synthesized and characterized by single crystal structure determinations, solid state 31P CPMAS NMR spectroscopy and low frequency vibrational spectroscopy. The two PBz3 ligands show different conformational structures and this is reflected in a distorted ‘P2CuX’ geometry for each complex. Solid state 31P CPMAS spectra show asymmetric quartets with 1J(31P–63Cu) ranging from 1.23 to 1.46 kHz and asymmetry parameters, dνCu, ranging from 8 × 109 to 13 × 109 Hz2. Reported also are the synthesis, structure, solid state 31P NMR and far-IR spectra of the two-co-ordinate complex [Cu(PBz3)2][CuCl2] and the crystal structure of the dimeric 1∶1 chloride complex, [Cu2(PBz3)2Cl2]·3C6H6, this latter structure being the first of this type reported for the PBz3 ligand. Attempts to synthesize a 1∶1 chloro complex using acetonitrile, rather than chloroform, as solvent led to the formation of tribenzylphosphine oxide. The conversion of [Cu2(PBz3)2Cl2]·3C6H6 into [Cu(PBz3)2][CuCl2] upon removal of benzene of solvation was followed by far-IR spectroscopy. The vibrational spectra of the bulk 1∶1 and 1∶2 complexes are consistent with the crystal structures. Bands due to the ν(CuX) modes of the neutral complexes and those due to the [CuX2]− ions in the ionic complexes have been assigned, and the relationship between the spectra and the structures of the compounds is discussed. p

CRYSTAL STRUCTURE, SOLID-STATE NMR STUDIES AND IGLO CALCULATIONS OF 1-HYDROXYCYCLOHEXANEPHOSPHONIC ACID

Abstract X-ray diffraction of 1-hydroxycyclohexanephosphonic acid, C6H13O4P, gives the following crystal data: orthorhombic, P212121 (no. 19), a = 6.558(1), b = 7.644(2), c = 16.271(1) A, V = 815.65 A3, Z = 4, and Dx = 1.467 g/cm3. The molecular structure shows a chair conformation of the cyclohexane ring with the phosphonate group in equatorial position. The asymmetric unit consists of the formula unit. Solid-state 31P CP MAS NMR spectroscopy of different crystallization fractions of the title compound gives two sets of principal values of the nuclear magnetic shielding tensor caused by different modifications of the acid. According to IGLO caculations the most shielded component is almost along the P[dbnd]O bond. The results are compared with the principal values of some other C6 phosphonic acids.

SOLID-STATE NMR STUDIES AND CRYSTAL STRUCTURE OF THE LAWESSON-REAGENT

Abstract X-ray diffraction of the toluene solvate of the Lawesson reagent, C14H14O2P2S4.C7H3, gives the following crystal data: triclinic, PT (no. 2). a = 6.831 (2), b = 9.393 (3), c = 9.793 (3) A, α = 70.33 (2), β = 83.28 (2). γ = 71.35 (2)°, V = 560.6 A3, Z = 1, and D2 = 1.471 Mg m−3. The bond lengths and angles are very close to those observed in the solvent-free crystals. The toluene molecule is disordered over two positions related by an inversion center. The asymmetric unit consists of half the formula unit. This is consistent with the fact that the solid-state 31P CP MAS NMR spectrum gives one set of principal values of the nuclear magnetic shielding tensor. Similar values were obtained for solvates of other aromatic compounds such as benzene, o-dichlorobenzene, methoxybenzene and p-dimethoxybenzene. A comparison with the data for the solvent-free Lawesson reagent shows that the nuclear shielding depends not only on the molecular structure but can also be influenced by short intermolecular S==S dis...

Structural and solid-state 31P nuclear magnetic resonance studies on 1 : 1 : 1 mixed nitrogen and phosphine base complexes with copper(I) halides

1 : 1 : 1 Adducts of copper(I) halides with phosphine and amine donor ligands, [{CuX[PPh2(C6H4Me-o)](cpy)}2] and [{CuX(PPh3)(pip)}2](cpy = 4-cyanopyridine, pip = piperidine; X = Cl, Br or I) have been synthesized as crystalline dihalide-bridged binuclear complexes and characterized by single-crystal structure determinations and solid-state 31P cross-polarization magic angle spinning (CPMAS) NMR spectroscopy. The [{CuX[PPh2(C6H4Me-o)](cpy)}2] complexes are isomorphous with their PPh3 analogues, crystallizing as centrosymmetric dimers in space group P21/n with a≈ 15.5, b≈ 8.0, c≈ 18.7 Å, β≈ 104°(Z= 2 dimers). Introduction of the o-tolyl group into the phosphine ligand increases all of the Cu–p, Cu–N and Cu–X bond distances by 1–2% with the increase in Cu–X accommodated primarily by an increase in the Cu ⋯ Cu distances by 2–6%. For [{CuX(PPh3)(pip)}2] the chloride and bromide complexes are isomorphous, crystallizing in space group Pbca with a≈ 16.5, b≈ 18.0, c≈ 14.6 Å(Z= 4 dimers). The monomer/asymmetric units are disposed close to a centre of symmetry but the two Cu–X distances at each copper site differ by over 0.3 Å and the resultant ‘dimers’ are better described as associated monomers with three- rather than four-co-ordinate copper. The iodide complex crystallizes in space group P, with a= 17.442(9), b= 16.532(6), c= 13.801(3)Å, α= 92.78(2), β= 112.08(3), γ= 112.65(3)°(Z= 3 dimers). The unit cell contains independent centro- and non-centro-symmetric dimers with significant differences in the geometric parameters of the two. Differences in the Cu–X distances are much smaller than for the X = Cl and Br complexes. The piperidine ligand co-ordinates through the nitrogen lone pair with the Cu–N bond approximately perpendicular to the Cu2X2 plane and is disposed away from the Cu2X2 plane and towards the phosphine ligand for all dimers except the centrosymmetric iodide dimer. The Cu ⋯ Cu distances are 7–11% longer than those of the corresponding pyridine base complexes, but are shorter than those in complexes with acetonitrile as the base. The solid-state 31P CP MAS NMR spectra of the complexes at B= 9.4 T show well resolved asymmetric quartets arising from a combination of scalar and dipolar coupling between the quadrupolar spin 3/2; copper and the spin ½ phosphorus nuclei. The structural and spectroscopic data are discussed in relation to steric and electronic properties of the donor ligands and the influence of these on the size and shape of the Cu2X2 core.

Synthesis, solid state 31P CP-MAS NMR infrared and Raman studies of mercury(II) complexes of 1,3,5-triaza-7-phosphaadamantane (PTA)

Insoluble mercury(II) complexes of a water-soluble phosphine, 1,3,5-triaza-7-phosphaadamantane (PTA), have been studied by solid state 31P CP-MAS NMR, infrared and Raman spectroscopies. Complexes of the type (PTA)HgX2 show larger coordination chemical shifts but similar J(31P—199Hg) coupling constants to those previously observed for similar trialkylphosphine complexes. These complexes all appear to be dimeric or polymeric. The nitrate complex of the form (PTA)2Hg(NO3)2 has also been isolated and complexes of the type (PTA)4Hg2+ are shown to exist. Keywords: mercury(II) phosphine complexes, solid state 31P NMR studies.