Acta Cryst. (2008). E64, i84 [ doi:10.1107/S1600536808038518 ]
Disilver(I) palladium(II) diphosphate, Ag2PdP2O7, is isotypic with Na2PdP2O7. It consists of infinite diphosphato-palladate(II) [Pd(P2O7)2/2]2- ribbons with the PdII ion in an almost square-planar coordination (
symmetry) and the P2O7 group exhibiting 2 symmetry. The [Pd(P2O7)2/2]2- ribbons are linked by distorted [AgO6] octahedra. 31P-MAS NMR studies on Ag2PdP2O7 are in accordance with one independent site for phosphorus; its isotropic chemical shift ![[delta]](/logos/entities/delta_rmgif.gif)
iso = 21.5 p.p.m. is similar to that of Pd2P2O7.
Microcrystalline Ag2PdP2O7 was synthesized via a solid state reaction by heating an amorphous precursor for 24 h at T = 773 K in air. The precursor was obtained by drying a mixture of 100.0 mg (0.94 mmol) palladium powder (99.99%, UMICORE AG, Hanau–Wolfgang) with an excess of conc. nitric acid and stoichiometric amounts of 319.2 mg AgNO3 (1.88 mmol) (p.A., Merck) and 18.8 ml H3PO4 (0.1 M) at 423 K as a brownish powder.
Isothermal heating of 100.0 mg (0.82 mmol) PdO, 189.3 mg (0.82 mmol) Ag2O (p.A. Merck) and 116.0 mg (0.41 mmol) P4O10 (99%, Riedel de Häen) (addition of 8.0 mg PdCl2 as mineralizer) carried out in sealed and evacuated silica tubes at 773 K for seven days gave besides microcrystalline, single-phase Ag2PdP2O7 (eq. 1) also small amounts of yellow plate-like single crystals which were distributed over the whole ampoule.
PdOs + Ag2Os + 1/2 P4O10,s → Ag2PdP2O7,s (eq. 1)
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: WinGX (Farrugia, 1999).
![[Figure 1]](./br2086fig1thm.gif)
| Fig. 1. Projection of the crystal structure of Ag2PdP2O7 along [010] with tetrahedral [PO4] units (yellow), Pd2+ (red) and Ag+ grey (DIAMOND v3.1f). |
![[Figure 2]](./br2086fig2thm.gif)
| Fig. 2. Diphosphato-palladate(II) ribbon [Pd(P2O7)2/2]2- along [001]. Thermal elipsoids with 50% probability (DIAMOND, v3.1f). |
| Ag2PdP2O7 | F(000) = 904 |
| Mr = 496.10 | The lattice parameters given were refined with the program SOS (Soose & Meyer, 1980), using 40 reflections from a Guinier IP photograph. |
| Monoclinic, C2/c | Dx = 5.008 Mg m−3 |
| Hall symbol: -C 2yc | Mo Kα radiation, λ = 0.71073 Å |
| a = 15.739 (2) Å | Cell parameters from 40 reflections |
| b = 5.7177 (7) Å | θ = 6.3–34.3° |
| c = 8.187 (1) Å | µ = 9.08 mm−1 |
| β = 116.75 (1)° | T = 293 K |
| V = 657.91 (15) Å3 | Prism, yellow |
| Z = 4 | 0.08 × 0.05 × 0.05 mm |
| Enraf–Nonius CAD-4 diffractometer | 591 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.080 |
| graphite | θmax = 29.9°, θmin = 2.9° |
| Nonprofiled ω scans | h = −22→22 |
| Absorption correction: ψ scan (North et al., 1968) | k = −8→0 |
| Tmin = 0.551, Tmax = 0.631 | l = −11→11 |
| 1890 measured reflections | 3 standard reflections every 60 min |
| 947 independent reflections | intensity decay: none |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.035 | w = 1/[σ2(Fo2) + (0.0245P)2] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.074 | (Δ/σ)max < 0.001 |
| S = 0.97 | Δρmax = 1.30 e Å−3 |
| 947 reflections | Δρmin = −1.14 e Å−3 |
| 58 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 0 restraints | Extinction coefficient: 0.00104 (17) |
| 0 constraints |
| Ag2PdP2O7 | V = 657.91 (15) Å3 |
| Mr = 496.10 | Z = 4 |
| Monoclinic, C2/c | Mo Kα radiation |
| a = 15.739 (2) Å | µ = 9.08 mm−1 |
| b = 5.7177 (7) Å | T = 293 K |
| c = 8.187 (1) Å | 0.08 × 0.05 × 0.05 mm |
| β = 116.75 (1)° |
| Enraf–Nonius CAD-4 diffractometer | 591 reflections with I > 2σ(I) |
| Absorption correction: ψ scan (North et al., 1968) | Rint = 0.080 |
| Tmin = 0.551, Tmax = 0.631 | θmax = 29.9° |
| 1890 measured reflections | 3 standard reflections every 60 min |
| 947 independent reflections | intensity decay: none |
| R[F2 > 2σ(F2)] = 0.035 | Δρmax = 1.30 e Å−3 |
| wR(F2) = 0.074 | Δρmin = −1.14 e Å−3 |
| S = 0.97 | Absolute structure: ? |
| 947 reflections | Flack parameter: ? |
| 58 parameters | Rogers parameter: ? |
| 0 restraints |
Geometry. All e.s.d.'s are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances and angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
| x | y | z | Uiso*/Ueq | ||
| Pd1 | 0 | 0 | 0 | 0.0145 (2) | |
| Ag1 | 0.23426 (5) | 0.85894 (13) | 0.79398 (9) | 0.0217 (2) | |
| P1 | 0.10116 (14) | 0.3445 (4) | 0.8422 (3) | 0.0137 (4) | |
| O1 | 0.8200 (4) | 0.5226 (10) | 0.5959 (7) | 0.0177 (13) | |
| O2 | 0 | 0.4744 (14) | 0.75 | 0.0139 (16) | |
| O3 | 0.8949 (4) | 0.1859 (11) | 0.8057 (7) | 0.0220 (14) | |
| O4 | 0.6031 (4) | 0.2953 (11) | 0.5045 (8) | 0.0213 (14) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Pd1 | 0.0103 (4) | 0.0178 (5) | 0.0135 (4) | −0.0012 (4) | 0.0036 (3) | 0.0055 (4) |
| Ag1 | 0.0197 (4) | 0.0247 (4) | 0.0171 (3) | −0.0044 (3) | 0.0050 (3) | −0.0017 (3) |
| P1 | 0.0111 (9) | 0.0152 (11) | 0.0146 (9) | −0.0028 (9) | 0.0055 (8) | 0.0003 (10) |
| O1 | 0.016 (3) | 0.016 (3) | 0.019 (3) | 0.011 (3) | 0.006 (2) | 0.005 (3) |
| O2 | 0.014 (4) | 0.011 (4) | 0.015 (4) | 0 | 0.006 (3) | 0 |
| O3 | 0.018 (3) | 0.027 (4) | 0.019 (3) | −0.003 (3) | 0.007 (3) | 0.010 (3) |
| O4 | 0.011 (3) | 0.026 (4) | 0.023 (3) | 0.004 (3) | 0.004 (2) | −0.012 (3) |
| Pd1—O4i | 1.987 (5) | P1—O4x | 1.539 (6) |
| Pd1—O4ii | 1.987 (5) | P1—O2 | 1.605 (4) |
| Pd1—O3iii | 2.007 (6) | O1—P1vii | 1.505 (6) |
| Pd1—O3iv | 2.007 (6) | O1—Ag1xi | 2.321 (5) |
| Ag1—O1v | 2.321 (5) | O1—Ag1vii | 2.436 (6) |
| Ag1—O4vi | 2.368 (6) | O2—P1xii | 1.605 (4) |
| Ag1—O1vii | 2.436 (6) | O3—P1vii | 1.537 (6) |
| Ag1—Ag1viii | 3.0427 (6) | O3—Pd1xiii | 2.007 (6) |
| Ag1—Ag1ix | 3.0427 (6) | O4—P1xiv | 1.539 (6) |
| P1—O1vii | 1.505 (6) | O4—Pd1xv | 1.987 (5) |
| P1—O3vii | 1.537 (6) | O4—Ag1xvi | 2.368 (5) |
| O4i—Pd1—O4ii | 180.0 (4) | Ag1viii—Ag1—Ag1ix | 139.96 (5) |
| O4i—Pd1—O3iii | 94.5 (2) | O1vii—P1—O3vii | 110.2 (3) |
| O4ii—Pd1—O3iii | 85.5 (2) | O1vii—P1—O4x | 111.6 (3) |
| O4i—Pd1—O3iv | 85.5 (2) | O3vii—P1—O4x | 112.4 (4) |
| O4ii—Pd1—O3iv | 94.5 (2) | O1vii—P1—O2 | 109.8 (4) |
| O3iii—Pd1—O3iv | 180.0 (6) | O3vii—P1—O2 | 106.6 (3) |
| O1v—Ag1—O4vi | 159.7 (2) | O4x—P1—O2 | 106.0 (3) |
| O1v—Ag1—O1vii | 88.23 (19) | P1vii—O1—Ag1xi | 123.5 (3) |
| O4vi—Ag1—O1vii | 87.5 (2) | P1vii—O1—Ag1vii | 141.5 (3) |
| O1v—Ag1—Ag1viii | 116.60 (15) | Ag1xi—O1—Ag1vii | 91.77 (19) |
| O4vi—Ag1—Ag1viii | 77.30 (15) | P1xii—O2—P1 | 124.9 (5) |
| O1vii—Ag1—Ag1viii | 57.82 (14) | P1vii—O3—Pd1xiii | 128.7 (3) |
| O1v—Ag1—Ag1ix | 84.21 (15) | P1xiv—O4—Pd1xv | 126.2 (3) |
| O4vi—Ag1—Ag1ix | 93.96 (16) | P1xiv—O4—Ag1xvi | 127.8 (3) |
| O1vii—Ag1—Ag1ix | 161.97 (14) | Pd1xv—O4—Ag1xvi | 105.4 (2) |
| Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) x−1, y, z−1; (iv) −x+1, −y, −z+1; (v) x−1/2, −y+3/2, z+1/2; (vi) x−1/2, y+1/2, z; (vii) −x+1, y, −z+3/2; (viii) −x+1/2, y−1/2, −z+3/2; (ix) −x+1/2, y+1/2, −z+3/2; (x) x−1/2, −y+1/2, z+1/2; (xi) x+1/2, −y+3/2, z−1/2; (xii) −x, y, −z+3/2; (xiii) x+1, y, z+1; (xiv) x+1/2, −y+1/2, z−1/2; (xv) −x+1/2, y+1/2, −z+1/2; (xvi) x+1/2, y−1/2, z. |
We thank Dr M. Schöneborn (University of Bonn) for the data collection. For the 31P-MAS NMR measurement we thank Dr W. Hoffbauer (University of Bonn). A noble metal donation by UMICORE AG (Hanau–Wolfgang) is gratefully acknowledged.
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With the synthesis and crystal structure refinement of the first gold phosphate AuIIIPO4 (Panagiotidis et al., 2005a) and two modifications of IrIII(PO3)3 (Panagiotidis et al., 2008) we have widened the crystal chemical knowledge on anhydrous phosphates of the noble metals. Investigations in the ternary system Pd/P/O provided, apart from the already existing phosphates Pd(PO3)2 (Palkina et al., 1978) and Pd2P2O7 (Panagiotidis et al., 2005b), no evidence for further thermodynamically stable palladium phosphates. Due to our interest in network structures built from square-planar units [MO4] (M = PdII, AuIII) and phosphate tetrahedra we focused therefore our search on polynary palladium phosphates. Polynary phosphates of divalent palladium are rare in literature. Up to now, only the compositions MI2PdP2O7 (M = Li (Laligant, 1992a), Na (Laligant, 1992b), K (El Maadi et al., 2003), K3.5Pd2.25(P2O7)2 (El Maadi et al., 2003) and Cs2Pd3(P2O7)2 (Lii et al., 2004) were reported. In Pd2P2O7 itself, Li2PdP2O7, and Na2PdP2O7 infinite ribbons [Pd(P2O7)2/2]2- are the characteristic structural motif. K2PdP2O7 adopts a layer structure with the crystal chemical composition [Pd(P2O7)4/4]2-. The structures of K3.5Pd2.25(P2O7)2 and Cs2Pd3(P2O7)2 consist of [PdIIO4] and [P2O7] groups generating a three-dimensional framework.
According to our X-ray single-crystal study Ag2PdP2O7 is isotypic to Na2PdP2O7. The unit cell contains four formula units Ag2PdP2O7 with one crystallographically independent site for silver, palladium and phosphorus (Fig. 1). As in the crystal structures of PdO (Waser et al., 1953), M-PdIISO4 (Dahmen et al., 1994), PdII(NO3)2(H2O)2 (Laligant et al., 1991), and Pd2P2O7 the Pd2+ ions show a square-planar coordination by oxygen. In Ag2PdP2O7 palladium is coordinated in a chelating way by two [P2O7] groups. This coordination mode, with a, for such diphosphates typically observed, bridging angle 〈(P—O2—P) = 124.9°, leads to the formation of corrugated ribbons [Pd(P2O7)2/2]2- (Fig. 2). These ribbons are linked by significantly distorted [AgIO6] octahedra. Due to different crystal chemical environment of the four independent oxygen atoms, with O1 forming one bond to P and two to Ag, O2 forming two bonds to P and O3 and O4 forming one bond each to P, Pd and Ag, a radial distortion of the phosphate groups with one very short, two medium long and one elongated distance d(P—O) is observed. In accordance with the crystal structure of Ag2PdP2O7 31P-MAS-NMR investigations (Varian Infinity Plus, 9.4 tesla-magnet, 2.5-mm MAS double resonance NMR probe, rotation frequency 3.0 kHz) show the presence of just one phosphorus site. Chemical shift parameters were determined by means of numerically calculated spectra (programme SIMPSON (Bak et al., 2000), MINUIT routine in SIMPSON (Vosegaard et al., 2002)) to δiso = 21.5 p.p.m., δaniso = 79.0 p.p.m. and η = 0.87. The chemical shifts are reported in parts per million (p.p.m.) from the external standard 85% H3PO4. As in Pd2P2O7 (η = 0.86) and in contrast to other diphosphates (Moreno et al., 2002; Griffiths et al., 1986; Hayashi & Hayamizu, 1989) a remarkably high value for η is observed. The isotropical chemical shift of Ag2PdP2O7 which is similar to the one observed for Pd2P2O7 (δiso = 28.3 p.p.m.) is exceptionally high in comparison to δiso values of diphosphates of the alkaline and alkaline earth metals (Moreno et al., 2002; Griffiths et al., 1986; Hayashi & Hayamizu, 1989). We attribute this observation to significant covalency in the Pd—O interaction.