*Acta Cryst.* (2012). E**68**, i91 [ doi:10.1107/S1600536812045667 ]

Abstract top

The silver zinc hexadecaphosphide Ag_{3.73(4)}Zn_{2.27(4)}P_{16} is the first polyphosphide in the ternary system Ag/Zn/P. It was synthesized from stoichiometric mixtures of Ag, Zn and P in the molar ratio 4:2:16, using AgI as a mineralizing agent in a gas-phase-assisted reaction. Ag_{3.73(4)}Zn_{2.27(4)}P_{16} crystallizes in the Cu_{5}InP_{16} structure type. The asymmetric unit contains two Ag/Zn sites with mixed occupancies and four P sites. One of the Ag/Zn sites is located on a twofold rotation axis. The polyanionic [P_{16}]-substructure consists of corrugated six-membered rings that are connected into a layer *via* the 1-, 2-, 4- and 5-positions of the rings by a bridging P atom in each case. The layers extend parallel to the *bc* plane and are stacked along the *a* axis. Both Ag/Zn sites are tetrahedrally coordinated by P atoms.

Experimental

Ag_{3.73 (4)}Zn_{2.27 (4)}P_{16} was prepared by reaction from the elements Ag
(ChemPur, powder, 99.9%), Zn (Sigma-Aldrich, pices, 99.9%), and P (ChemPur,
powder, 99.999%) in the stoichiometric ratio of 4:2:16 in a 500 mg batch.
As mineralizing agent, 10 mg AgI (ChemPur, powder, 99.9%) per 500 mg total
sample weight was added. The reaction was carried out in evacuated ampoules
in a muffle furnace at 823 K during 14 days using a heating ratio of 70 K/h. The sample was cooled down slowly at a rate of 5 K/h. For X-ray powder
phase analyses a fraction of the sample was ground. Phase purity has been
substantiated. Single crystals of suitable size for a
single-crystal structure determination could be separated from the bulk phase.
The sample was stable under atmospheric conditions for months.

Refinement

The mixed-occupied Ag/Zn sites
are located on Wyckoff positions 4*e* and 8*f*. The
refinement of the Ag and Zn content was constrained to an overall full
occupancy according to the sum of the two elements, each of them located
on the same coordinates and with the same displacement parameters.
The ratio of the two elements has been refined unrestricted.

Computing details top

Data collection: *X-AREA* (Stoe & Cie, 2011); cell refinement: *X-AREA* (Stoe & Cie, 2011); data reduction: *X-AREA* (Stoe & Cie, 2011); program(s) used to solve structure: *SUPERFLIP* (Palatinus & Chapuis 2007); program(s) used to refine structure: *JANA2006* (Petřiček *et al.*, 2006); molecular graphics: *DIAMOND* (Brandenburg & Putz, 2005); software used to prepare material for publication: *publCIF* (Westrip, 2010).

Figures top

Silver zinc hexadecaphosphide top

Crystal data top

Ag_{3.73}Zn_{2.27}P_{16} | F(000) = 966 |

M = 1046.3_{r} | D_{x} = 4.17 Mg m^{−}^{3} |

Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |

Hall symbol: -C 2yc | Cell parameters from 4528 reflections |

a = 11.492 (1) Å | θ = 2.8–30.5° |

b = 9.9604 (8) Å | µ = 9.05 mm^{−}^{1} |

c = 7.7106 (9) Å | T = 293 K |

β = 109.585 (9)° | Isomorphic, black |

V = 831.5 (2) Å^{3} | 0.02 × 0.02 × 0.02 mm |

Z = 2 |

Data collection top

IPDS Stoe 2T diffractometer | 1265 independent reflections |

Radiation source: X-ray tube | 1135 reflections with I > 3σ(I) |

Plane graphite monochromator | R_{int} = 0.015 |

Detector resolution: 6.67 pixels mm^{-1} | θ_{max} = 30.5°, θ_{min} = 2.8° |

rotation method scans | h = −16→16 |

Absorption correction: numerical ( X-AREA; Stoe & Cie, 2011) | k = −13→14 |

T_{min} = 0.730, T_{max} = 0.771 | l = −10→10 |

4398 measured reflections |

Refinement top

Refinement on F^{2} | 14 constraints |

R[F^{2} > 2σ(F^{2})] = 0.018 | Weighting scheme based on measured s.u.'s w = 1/(σ^{2}(I) + 0.0004I^{2}) |

wR(F^{2}) = 0.042 | (Δ/σ)_{max} = 0.038 |

S = 1.39 | Δρ_{max} = 0.56 e Å^{−}^{3} |

1265 reflections | Δρ_{min} = −0.66 e Å^{−}^{3} |

54 parameters | Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974) |

0 restraints | Extinction coefficient: 0.084 (5) |

Crystal data top

Ag_{3.73}Zn_{2.27}P_{16} | V = 831.5 (2) Å^{3} |

M = 1046.3_{r} | Z = 2 |

Monoclinic, C2/c | Mo Kα radiation |

a = 11.492 (1) Å | µ = 9.05 mm^{−}^{1} |

b = 9.9604 (8) Å | T = 293 K |

c = 7.7106 (9) Å | 0.02 × 0.02 × 0.02 mm |

β = 109.585 (9)° |

Data collection top

IPDS Stoe 2T diffractometer | 1265 independent reflections |

Absorption correction: numerical ( X-AREA; Stoe & Cie, 2011) | 1135 reflections with I > 3σ(I) |

T_{min} = 0.730, T_{max} = 0.771 | R_{int} = 0.015 |

4398 measured reflections |

Refinement top

R[F^{2} > 2σ(F^{2})] = 0.018 | 54 parameters |

wR(F^{2}) = 0.042 | 0 restraints |

S = 1.39 | Δρ_{max} = 0.56 e Å^{−}^{3} |

1265 reflections | Δρ_{min} = −0.66 e Å^{−}^{3} |

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^{2}) top

x | y | z | U_{iso}*/U_{eq} | Occ. (<1) | |

Ag1 | 0 | 0.41699 (3) | 0.25 | 0.01075 (10) | 0.422 (6) |

Zn1 | 0 | 0.41699 (3) | 0.25 | 0.01075 (10) | 0.578 (6) |

Ag2 | −0.089927 (17) | 0.13768 (2) | −0.08750 (3) | 0.01608 (7) | 0.721 (7) |

Zn2 | −0.089927 (17) | 0.13768 (2) | −0.08750 (3) | 0.01608 (7) | 0.279 (7) |

P1 | −0.16624 (5) | 0.56752 (5) | 0.05996 (7) | 0.00731 (15) | |

P2 | −0.24029 (5) | 0.32264 (5) | −0.24701 (7) | 0.00785 (15) | |

P3 | 0.09157 (4) | 0.27552 (6) | 0.07194 (7) | 0.00827 (15) | |

P4 | −0.33325 (5) | 0.48032 (5) | −0.14361 (8) | 0.00915 (15) |

Atomic displacement parameters (Å^{2}) top

U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} | |

Ag1 | 0.01067 (15) | 0.01146 (16) | 0.01117 (17) | 0 | 0.00506 (10) | 0 |

Zn1 | 0.01067 (15) | 0.01146 (16) | 0.01117 (17) | 0 | 0.00506 (10) | 0 |

Ag2 | 0.01637 (11) | 0.01572 (12) | 0.01331 (12) | −0.00637 (6) | 0.00121 (7) | −0.00034 (6) |

Zn2 | 0.01637 (11) | 0.01572 (12) | 0.01331 (12) | −0.00637 (6) | 0.00121 (7) | −0.00034 (6) |

P1 | 0.0079 (2) | 0.0074 (2) | 0.0071 (2) | 0.00021 (16) | 0.00310 (17) | 0.00069 (17) |

P2 | 0.0090 (2) | 0.0076 (2) | 0.0072 (2) | −0.00064 (16) | 0.00309 (17) | −0.00022 (18) |

P3 | 0.0077 (2) | 0.0082 (2) | 0.0093 (3) | 0.00004 (16) | 0.00342 (18) | 0.00121 (17) |

P4 | 0.0096 (2) | 0.0104 (2) | 0.0080 (2) | −0.00069 (17) | 0.00363 (17) | −0.00171 (18) |

Geometric parameters (Å, º) top

Ag1—P1 | 2.4836 (7) | Ag2—P4^{iii} | 2.5280 (7) |

Ag1—P1^{i} | 2.4836 (7) | P1—P2^{iv} | 2.2328 (9) |

Ag1—P3 | 2.4385 (7) | P1—P3^{v} | 2.1909 (9) |

Ag1—P3^{i} | 2.4385 (7) | P1—P4 | 2.2095 (9) |

Ag2—P2 | 2.5432 (7) | P2—P3^{vi} | 2.1976 (8) |

Ag2—P3 | 2.4551 (7) | P2—P4 | 2.1941 (9) |

Ag2—P4^{ii} | 2.5115 (7) | ||

P1—Ag1—P1^{i} | 105.73 (2) | Ag2—P2—P4 | 132.64 (3) |

P1—Ag1—P3 | 114.11 (2) | P1^{vii}—P2—P3^{vi} | 104.18 (3) |

P1—Ag1—P3^{i} | 106.81 (2) | P1^{vii}—P2—P4 | 103.43 (3) |

P1^{i}—Ag1—P3 | 106.81 (2) | P3^{vi}—P2—P4 | 96.77 (3) |

P1^{i}—Ag1—P3^{i} | 114.11 (2) | Ag1—P3—Ag2 | 98.66 (2) |

P3—Ag1—P3^{i} | 109.40 (2) | Ag1—P3—Zn2 | 98.66 (2) |

P2—Ag2—P3 | 99.36 (2) | Ag1—P3—P1^{v} | 99.15 (3) |

P2—Ag2—P4^{ii} | 93.38 (2) | Ag1—P3—P2^{viii} | 110.66 (3) |

P2—Ag2—P4^{iii} | 109.66 (2) | Ag2—P3—P1^{v} | 124.46 (3) |

P3—Ag2—P4^{ii} | 140.08 (2) | Ag2—P3—P2^{viii} | 119.19 (3) |

P3—Ag2—P4^{iii} | 110.23 (2) | P1^{v}—P3—P2^{viii} | 102.39 (3) |

P4^{ii}—Ag2—P4^{iii} | 100.52 (2) | Ag2^{ix}—P4—Ag2^{iii} | 139.72 (3) |

Ag1—P1—P2^{iv} | 106.99 (3) | Ag2^{ix}—P4—Zn2^{iii} | 139.72 (3) |

Ag1—P1—P3^{v} | 111.18 (3) | Ag2^{ix}—P4—P1 | 108.81 (3) |

Ag1—P1—P4 | 119.67 (3) | Ag2^{ix}—P4—P2 | 103.06 (3) |

P2^{iv}—P1—P3^{v} | 104.82 (3) | Ag2^{iii}—P4—Zn2^{ix} | 139.72 (3) |

P2^{iv}—P1—P4 | 103.40 (3) | Ag2^{iii}—P4—P1 | 96.17 (3) |

P3^{v}—P1—P4 | 109.44 (3) | Ag2^{iii}—P4—P2 | 104.53 (3) |

Ag2—P2—P1^{vii} | 109.17 (3) | P1—P4—P2 | 97.28 (3) |

Ag2—P2—P3^{vi} | 107.16 (3) |

Symmetry codes: (i) −x, y, −z+1/2; (ii) −x−1/2, y−1/2, −z−1/2; (iii) −x−1/2, −y+1/2, −z; (iv) x, −y+1, z+1/2; (v) −x, −y+1, −z; (vi) x−1/2, −y+1/2, z−1/2; (vii) x, −y+1, z−1/2; (viii) x+1/2, −y+1/2, z+1/2; (ix) −x−1/2, y+1/2, −z−1/2. |

Experimental details

Crystal data | |

Chemical formula | Ag_{3.73}Zn_{2.27}P_{16} |

M_{r} | 1046.3 |

Crystal system, space group | Monoclinic, C2/c |

Temperature (K) | 293 |

a, b, c (Å) | 11.492 (1), 9.9604 (8), 7.7106 (9) |

β (°) | 109.585 (9) |

V (Å^{3}) | 831.5 (2) |

Z | 2 |

Radiation type | Mo Kα |

µ (mm^{−}^{1}) | 9.05 |

Crystal size (mm) | 0.02 × 0.02 × 0.02 |

Data collection | |

Diffractometer | IPDS Stoe 2T diffractometer |

Absorption correction | Numerical ( X-AREA; Stoe & Cie, 2011) |

T_{min}, T_{max} | 0.730, 0.771 |

No. of measured, independent and observed [ I > 3σ(I)] reflections | 4398, 1265, 1135 |

R_{int} | 0.015 |

(sin θ/λ)_{max} (Å^{−}^{1}) | 0.713 |

Refinement | |

R[F^{2} > 2σ(F^{2})], wR(F^{2}), S | 0.018, 0.042, 1.39 |

No. of reflections | 1265 |

No. of parameters | 54 |

Δρ_{max}, Δρ_{min} (e Å^{−}^{3}) | 0.56, −0.66 |

Computer programs: *X-AREA* (Stoe & Cie, 2011), *SUPERFLIP* (Palatinus & Chapuis 2007), *JANA2006* (Petřiček *et al.*, 2006), *DIAMOND* (Brandenburg & Putz, 2005), *publCIF* (Westrip, 2010).

Acknowledgements top

The authors thank the German Science Foundation (DFG) for the kind support of project NI1095/1–2.

Herein we report on Ag

_{3.73 (4)}Zn_{2.27 (4)}P_{16}(silver zinc hexadecaphosphide), the first ternary compound in the system Ag/Zn/P. It crystallizes isostructurally to Cu_{5}InP_{16}in space groupC2/c(Langeet al., 2008). The asymmetric unit is built up by two mixed-occupied Ag/Zn sites and four P sites. Both Ag/Zn sites are tetrahedrally coordinated by four P atoms featuring bond lengths of 2.4386 (7) to 2.5432 (7) Å. The bond lengths of the (Ag1/Zn1) site to phosphorus range from 2.4386 (7) to 2.4836 (7) Å while slightly longer bond lengths of 2.4551 (7) to 2.5432 (7) Å are observed for (Ag2/Zn2). This finding is consistent with the higher amount of zinc on the (Ag1/Zn1) site leading to somewhat shorter bond lengths. For comparison, Zn—P bond length range from 2.36 to 2.40 Å in ZnP_{2}(Zaninet al., 2003) and ZnP_{4}(Dommannet al., 1989) while common Ag—P distances in polyphosphides are observed from 2.47 to 2.61 Å in Ag_{3}P_{11}(Möller & Jeitschko, 1981) and 2.50 to 2.69 Å in AgP_{2}(Olofsson, 1965), respectively. Mixed-occupied Ag/Zn sites are not uncommon and are observed, for example, in intermetallic phases like Ag_{4.5}Zn_{4.5}(or better AgZn; Edmunds & Qurashi, 1951). All P—P distances in Ag_{3.73 (4)}Zn_{2.27 (4)}P_{16}, ranging from 2.1909 (9) to 2.2328 (9) Å, are within the expected range for polyphosphides (Bawohl & Nilges, 2009).