Solid-state 31P CPMAS Research Articles

Direct Synthesis of Low-Coordinate Pd Catalysts Supported on SiO2 via Surface Organometallic Chemistry

Highly dispersed low-coordinate Pd sites on SiO2 are fabricated by grafting the PdII PCP-pincer complex (tBuPCP)Pd–OH (tBuPCP = 2,6-C6H3(CH2PtBu2)2) on SiO2, followed by calcination with ozone (100 °C) and reduction with H2 (300 °C). The chemisorption process and structure of this organometallic complex on SiO2 is established by solution-phase 1H and 31P NMR and solid-state 31P CPMAS NMR spectroscopy, XPS, DRIFTS, and AC-HAADF-STEM. The CO adsorption properties of the Pd centers reveal a surprisingly high fraction of adsorption sites where CO is bound in a linear fashion, indicative of low-coordinate Pd. Furthermore, enhanced selectivity of these catalyst centers in aerobic alcohol oxidation versus a control catalyst argues that these low-coordinate sites are the catalytically active sites.

Reaction products of titanium(IV) sulfate with the two, dimeric precursors, 1,2,3-tri-titanium(IV)- and 1,2-di-titanium(IV)-substituted α-Keggin polyoxometalates (POMs), under acidic conditions. A tetra-titanium(IV) oxide cluster and one coordinated sulfate ion grafted on a di-lacunary Keggin POM

Abstract A novel, monomeric species containing a tetra-titanium(IV) oxide cluster and one coordinated sulfate ion grafted on a di-lacunary Keggin polyoxometalate (POM), [[{Ti(H2O)3}2{Ti(H2O)2}2(μ-O)3(SO4)](PW10O37)]− 1, was derived from reactions of Ti(SO4)2 with two precursors, i.e., [(α-1,2-PW10Ti2O38)2O2]10 − 2 and [(α-1,2,3-PW9Ti3O37)2O3]12 − 3, under strongly acidic conditions. [Note: the potassium salts of POMs 1–3 are represented as K1 to K3, respectively.] The potassium salt of 1, which was stable in the solid state, but unstable in water, was unequivocally characterized by complete elemental analysis, TG/DTA, FTIR, X-ray crystallography, and solid-state 31P CPMAS and solution 31P NMR spectroscopy. Both precursors have been considered as relatively stable forms of titanium(IV)-substituted Keggin POMs. A deposit of crystals from the reaction system consisting of precursor 3, Ti(SO4)2, and a strong acid (HCl, HNO3, or H2SO4) was significantly affected by the conjugate base of the acid, while crystallization from the reaction using precursor 2 was not affected by the base. The Ti4 center in 1 belongs to a class of a 2-host (di-lacunary site)/4-guest (four Ti atoms) coordination relationship, or a combination of two sets of a 1-host/2-guest coordination.

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).

Light-stable and antimicrobial active silver(I) complexes composed of triphenylphosphine and amino acid ligands: Synthesis, crystal structure, and antimicrobial activity of silver(I) complexes constructed with hard and soft donor atoms ( n∞{[Ag(L)(PPh 3)] 2} with L = α-ala − or asn − and n = 1 or 2)

Three novel silver(I) complexes consisting of both hard Lewis bases (O and N atoms) and one soft Lewis base (P atom) (( dl-α-alaninato)(triphenylphosphine)silver(I) ( 1), ( dl-asparaginato) (triphenylphosphine)silver(I) ( 2) and ( l-asparaginato) (triphenylphosphine)silver(I) ( 3)) were prepared from stoichiometric reactions of amino acid–silver(I) complexes with PPh 3 in a 1:1 molar ratio in a mixed organic solvent. These silver(I) complexes were soluble in organic solvents but insoluble in water; they are also more light-stable as compared to the corresponding precursors, amino acid–silver(I) complexes. Their solid-state and solution structures were unequivocally characterized using elemental analysis, TG/DTA, FTIR, X-ray structure analysis, solution ( 1H, 13C, and 31P) NMR and solid-state 31P CPMAS NMR spectroscopy. The X-ray structure analysis of complexes 1 and 2 revealed that these complexes were dimers with an inversion center. Each silver(I) atom was coordinated in a distorted four-coordinate environment containing an AgNO 2P core. Complexes 1 and 2 formed 1D and 2D networks in the crystal through intermolecular hydrogen bonding networks that can be described as ∞{[Ag( dl-α-ala)(PPh 3)] 2 · 2H 2O} and 2 ∞{[Ag( dl-asn)(PPh 3)] 2 · 2H 2O · 2EtOH}, respectively. Complexes 1– 3 showed moderate to modest antimicrobial activities against selected bacteria and yeasts in a water-suspension system.

Copper(I) O , O ′-dialkyldithiophosphate clusters: EXAFS, NMR and X-ray diffraction studies

Copper K-edge EXAFS data for six polycrystalline cubic cluster compounds, {Cu8[S2P(OR)2]6(μ8-S)} with R = Et, n Pr, i Pr, n Bu, i Bu and i Am, show that the architecture of their Cu8(S2P)2S cores is fairly rigid and independent of both length and branching of the alkyl chain, and that the structure of the cluster is maintained in acetone solution. Solid-state 31P CP-MAS and static 65Cu NMR data for {Cu8[S2P(O n Pr)2]6(μ8-S)} and {Cu8[S2P(OEt)2]6(μ8-S)} show similarities in the icosahedral O,O′-dialkyldithiophosphate shells and in the ‘cubic’ copper cores in these cluster compounds. The crystal structure of {Cu8[S2P(O n Pr)2]6(μ8-S)} was resolved using single-crystal X-ray diffraction.

Syntheses, Structures, and Antimicrobial Activities of Light-Stable and Di- and Mononuclear Silver(I) Carboxylate Complexes Composed of Triphenylphosphine, and Chiral and Racemic Forms of 2-Pyrrolidone-5-carboxylic Acid (H2pyrrld). A Variety of Ag–O Bonding Modes in the Silver(I) Complexes Constructed with Hard Oxygen and Soft Phosphorus Atoms

Abstract Using light-stable dimeric silver(I) carboxylate precursors {[Ag(Hpyrrld)]2}n formed with chiral and racemic forms of 2-pyrrolidone-5-carboxylic acid (H2pyrrld) ligand, six novel light-stable, triphenylphosphinesilver(I) complexes consisting of both a hard Lewis base (O atom) and a soft Lewis base (P atom) were prepared, i.e. [Ag2(R-Hpyrrld)2(H2O)(PPh3)2]·H2O (1), [Ag(R-Hpyrrld)(PPh3)2]2 (2), [Ag2(S-Hpyrrld)2(H2O)(PPh3)2]·H2O (3), [Ag(S-Hpyrrld)(PPh3)2]2 (4), {[Ag(R,S-Hpyrrld)(PPh3)]2}n (5), and [Ag(R,S-Hpyrrld)(PPh3)2] (6). Their solid-state and solution structures were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray structure analysis, molecular weight measurements in EtOH with the vaporimetric method, solution (1H, 13C, and 31P) NMR, and solid-state 31P CPMAS NMR spectroscopy. Two sets of the enantiomeric complexes were isolated as (1 and 3) and (2 and 4). X-ray crystallography revealed that these complexes possessed different Ag–O bonding modes, depending on the number of PPh3 ligands and the chirality of the Hpyrrld− ligand. The complexes 1–6 behaved as a monomeric species in EtOH and CD2Cl2. The antimicrobial activites by the silver(I) complexes in the water–suspension system against selected bacteria, yeast, and molds, were significantly correlated with the number of coordinating PPh3 ligands per silver(I) atom in the complexes.

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

Co-ordination and conformational isomerism in bis(tricyclohexylphosphine) gold(I) halides

Solid state complexes of bis(tricyclohexylphosphine)gold(I) with halide counter ions, Au(PCy3)2X (X = Cl, Br or I), have been crystallised from solutions of [NBu4][AuX2] and PCy3 in dimethylformamide and characterised by single crystal structure determinations, far-infrared spectroscopy and solid state 31P CP MAS NMR spectroscopy. The results show the complexes crystallise as a unique array of co-ordination and conformational isomers which reflect the conformational flexibility of the tricyclohexylphosphine ligand and the relative preferences of the halide anions for C–H· · ·X–versus Au+· · ·X– bonding interactions. The chloride crystallises as a single ionic complex, [Au(PCy3)2]+Cl–, with the gold two-co-ordinate and the cations and anions well separated in the crystal lattice. The bromide crystallises as three different polymorphs with four distinct molecular structures. The first (α) form crystallises as ionic [Au(PCy3)2]+Br– with the bromide adjacent to but not co-ordinated to the gold. The second (β) form presents two crystallographically independent [Au(PCy3)2Br] molecules with semi-co-ordinated bromide and significant differences in the conformational dispositions of the PCy3 ligands. The third (γ) form crystallises as [Au(PCy3)2Br] with fully co-ordinated bromide. The iodide crystallises with semi-co-ordinated and co-ordinated iodide in [Au(PCy3)2I]·PCy3 and [Au(PCy3)2I] complexes respectively. The study provides an unusual series of molecular ‘vignettes’ in which the response of the [Au(PCy3)2]+ cation to halide anion can be monitored as it passes through the ligand substituents and co-ordinates to the central gold atom.

Structural and 31P CP MAS NMR spectroscopic studies of the P2CuN2 copper(I) complexes [Cu(PPh3)2(MeCN)2]X for X = PF6, BF4 and ClO4

The mixed ligand P2CuN2 copper(I) complexes [Cu(PPh3)2(MeCN)2]X have been studied by one- and two-dimensional 31P CP MAS NMR spectroscopy for X = PF6, BF4 or ClO4 and single crystal X-ray diffraction for X = PF6 and ClO4, completing availability of precise structural data for this isomorphous series. The compounds crystallise as discrete cations and anions in space group P21/n with a ≈ 15, b ≈ 27, c ≈ 9 A, β = 95°, Z = 4. The anion is located ca. 6 A from the copper atom and adjacent to a cleft formed between the acetonitrile ligands and phosphine ligand 2 while the crystallographically independent PPh3 ligands adopt staggered three-bladed propeller-type conformations of opposite chirality. The geometric symmetry of the P2CuN2 co-ordination sphere is low with Cu–P(1) 2.276(4)–2.287(2), Cu–P(2) 2.258(4)–2.269(1) A, Cu–N 2.023(9)–2.053(3) A, P–Cu–P 126.82(4)–127.73(5), N–Cu–N 99.5(4)–100.3(1), P(1)–Cu–N 100.87(8)–102.34(9) and P(2)–Cu–N 110.4(1)–111.9(3)°. One- and two-dimensional solid state 31P CP MAS NMR spectra of the compounds at 9.40 T show chemical shift differences of 6 ppm between the signals arising from the two P sites which form part of an ABX spin system with 1J[31P(1)–63Cu] 1.13–1.14 kHz, 1J[31P(2)–63Cu] 1.30 kHz and 2J(31P–31P) 75 Hz. The copper quadrupolar induced distortion of the line spacings is different for the two sites and is postulated to be a consequence of variation in the angle between the Cu–P vectors and the z axis of the electric field gradient tensor. The magnitude of the distortion is relatively small and consistent with small copper quadrupolar coupling constants for the compounds and a balanced electronic charge distribution about the copper(I) site in spite of the low geometric symmetry of the P2CuN2 co-ordination sphere.

Structural Alternatives in R2(Cl)P:GaCl3 Systems (R = Alkyl, Phenyl), Including Examples of Intermolecular P → P Coordination

Systematic NMR studies of (dialkyl/diaryl)chlorophosphine−gallium chloride reaction mixtures reveal three structural alternatives, which are related by equilibria in solution, and their relative stability is dependent on the nature of the substituent (R = Me, Et, iPr, tBu, Ph) and the reaction stoichiometry. The coordination complex R2(Cl)P→GaCl3 is observed in all cases, and a derivative (R = iPr) has been crystallographically characterized. Tetrachlorogallate salts of the diphosphorus cations [R2(Cl)P−PR2]+ are observed for smaller R substituents (R = Me, Et, iPr, Ph), consistent with a previous report. Solid-state 31P CP-MAS NMR spectra distinguish the methyl derivative from the novel salt [Me2(Cl)P−P(Me2)−GaCl3][GaCl4], containing a phosphine−phosphenium−gallium chloride cation, which has been crystallographically characterized. Factors governing the relative stabilities of the structural alternatives are discussed, and comparisons are made between the isomeric forms for R2(Cl)P:GaCl3.

METHYLTRITHIOPHOSPHONIC ACID AND RELATED COMPOUNDS - SYNTHESIS, SOLUTION, AND SOLID-STATE NMR SPECTROSCOPY AS WELL AS SHIELDING TENSOR CALCULATIONS

Abstract Methyltrithiophosphonic acid (1) has been prepared in a pure state. The thermal decomposition of 1 into 2,4-dimethyl-2,4-dithio-1,3,2,4-dithiadiphosphetane (3) proceeds via dimethylpentathiodiphosphonic acid (2), which has been characterized by its 1H and 31P high resolution NMR parameters and by a derivatization reaction with norbornadiene. Solid-state 31P CP MAS spectra of 1, 3, and the related compounds, 3,5-dimethyl-3,5-dithio-1,2,4,3,5-trithiadiphospholane (4), and 3,6-dimethyl-3,6-dithio-1,2,4,5,3,6-tetrathiadiphosphorinane (5), have been measured. The experimentally determined phosphorus anisotropic shielding tensors are compared with results of IGLO calculations. From a comparison of the experimental values with those calculated for different geometry optimized conformations of 1, 4, and 5 structural assignments became possible: In the solid state 1 most probably shows a trans orientation of the H-S-P─S unit, 4 probably realizes a half-chair and 5 a chair conformation, both with bisaxial ...

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 Spectroscopic Studies on the Dimeric Complexes of Tris(2-methylphenyl)phosphine With Copper(I) Halides

1:1 adducts of the copper(I) halides, CuX (X = Cl, Br, I), with the sterically hindered ligand tris (2-methylphenyl) phospine [P(o- tol )3] have been synthesized as crystalline dihalo -bridged centrosymmetric binuclear species; six compounds have been characterized by solid-state CP-MAS n.m.r. and far-infrared spectroscopy and by room-temperature single-crystal X-ray structure determination. For X = Cl , the dimeric complex. [P(o- tol )3CuCl]2, with three-coordinate copper atoms has been obtained from acetonitrile solution. Similar dimeric complexes for X = Br and I were obtained from toluene solution, the iodide adduct incorporating cocrystallized toluene. The X = Br and I complexes crystallized from acetonitrile solution yield mixed- ligand four-coordinate copper(I) dimers, [( MeCN )P(o- tol )3CuX]2, the iodide as a 2MeCN solvate. An additional crystalline phase incorporating crystallographically independent molecules of both the three-coordinate dimer and the four-coordinate mixed- ligand dimer has also been characterized for X = Br. Solid-state 31P CP-MAS n.m.r. spectra of the complexes at B = 7.05 T show well resolved asymmetric quartets with a ∆v3/∆v1 of 1.4 for the PcuX2 complexes and 1.1-1.2 for the PcuX2N complexes; these results reflect the geometric and bonding changes in the copper coordination sphere. Far-infrared spectra of the complexes show two strong halogen-sensitive bands, with a wavenumber separation of 30-40 cm-1, which have been assigned to copper-halogen stretching modes v( CuX ), this assignment being supported by a normal coordinate analysis on the Cu2X2 core.

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.

Structural and Solid-State 31P N.M.R. Studies on a Novel Fluorotris(triphenyl-phosphine)copper(I) Adduct

The synthesis of the title compound as its triphenylphosphine /methanol solvate, [(PPh3)3CuF].- 4PPh3.4MeOH, is reported together with characterization by solid-state 31P CP-MAS n.m.r. and single-crystal X-ray diffraction. Crystals are trigonal, space group P3, with a 14.453(5), c 15.388(6)Ǻ. The structure refined to a final R value of 0.049 for 1926 'observed' [I> 3σ(I)] reflections. The (PPh3)3CuF molecule lies on a crystallographic threefold axis. Cu-F is 2.115(9)Ǻ, and Cu-P 2.323(3)Ǻ. The solid-state 31P n.m.r. spectrum is dominated by peaks from each of the four solvated PPh3 molecules at -1.6, -5.4, -10.6 and -14.2 ppm with respect to 85% H3PO4. The quartet of lines arising from the ligands coordinated to the copper atom shows an average chemical shift of -5 ppm and approximately equal line spacings of 1.0 kHz.