The layered polyphosphide Ag_3.73(4)Zn_2.27(4)P₁₆

The silver zinc hexa­deca­phosphide Ag_3.73(4)Zn_2.27(4)P₁₆ 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)P₁₆ crystallizes in the Cu₅InP₁₆ 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 [P₁₆]-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.

Related literature

For background to and structures of related polyphosphides, see: Bawohl & Nilges (2009); Dommann et al. (1989); Edmunds & Qurashi (1951); Lange et al. (2008); Möller & Jeitschko (1981); Olofsson (1965); Zanin et al. (2003). For background to the extinction correction, see: Becker & Coppens (1974).

Experimental

Crystal data

• Ag_3.73Zn_2.27P₁₆

• M_r = 1046.3

• Monoclinic, C 2/c

• a = 11.492 (1) Å

• b = 9.9604 (8) Å

• c = 7.7106 (9) Å

• β = 109.585 (9)°

• V = 831.5 (2) ų

• Z = 2

• Mo Kα radiation

• μ = 9.05 mm⁻¹

• T = 293 K

• 0.02 × 0.02 × 0.02 mm

Data collection

• IPDS Stoe 2T diffractometer

• Absorption correction: numerical (X-AREA; Stoe & Cie, 2011) T_min = 0.730, T_max = 0.771

• 4398 measured reflections

• 1265 independent reflections

• 1135 reflections with I > 3σ(I)

• R_int = 0.015

Refinement

• R[F² > 2σ(F²)] = 0.018

• wR(F²) = 0.042

• S = 1.39

• 1265 reflections

• 54 parameters

• Δρ_max = 0.56 e Å⁻³

• Δρ_min = −0.66 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2011); cell refinement: X-AREA; data reduction: X-AREA; 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).

Supporting information

S1. Comment

Herein we report on Ag_3.73 (4)Zn_2.27 (4)P₁₆ (silver zinc hexadecaphosphide), the first ternary compound in the system Ag/Zn/P. It crystallizes isostructurally to Cu₅InP₁₆ in space group C2/c (Lange et 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 ZnP₂ (Zanin et al., 2003) and ZnP₄ (Dommann et al., 1989) while common Ag—P distances in polyphosphides are observed from 2.47 to 2.61 Å in Ag₃P₁₁ (Möller & Jeitschko, 1981) and 2.50 to 2.69 Å in AgP₂ (Olofsson, 1965), respectively. Mixed-occupied Ag/Zn sites are not uncommon and are observed, for example, in intermetallic phases like Ag_4.5Zn_4.5 (or better AgZn; Edmunds & Qurashi, 1951). All P—P distances in Ag_3.73 (4)Zn_2.27 (4)P₁₆, ranging from 2.1909 (9) to 2.2328 (9) Å, are within the expected range for polyphosphides (Bawohl & Nilges, 2009).

Related literature

For background to and structures of related polyphosphides, see: Bawohl & Nilges (2009); Dommann et al. (1989); Edmunds & Qurashi (1951); Lange et al. (2008); Möller & Jeitschko (1981); Olofsson (1965); Zanin et al. (2003). For background to the extinction correction, see: Becker & Coppens (1974).

S2. Experimental

Ag_3.73 (4)Zn_2.27 (4)P₁₆ 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.

S3. Refinement

The mixed-occupied Ag/Zn sites are located on Wyckoff positions 4e and 8f. 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

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

Fig. 1. The crystal structure of Ag3.73 (4)Zn2.27 (4)P16, viewed along the c axis. The mixed Ag/Zn sites are drawn in turqueous and P atoms in blue, respectively. The displacement ellipsoids are shown at the 90% probability level.

Silver zinc hexadecaphosphide

Crystal data

Ag3.73Zn2.27P16	F(000) = 966
Mr = 1046.3	Dx = 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

IPDS Stoe 2T diffractometer	1265 independent reflections
Radiation source: X-ray tube	1135 reflections with I > 3σ(I)
Plane graphite monochromator	Rint = 0.015
Detector resolution: 6.67 pixels mm^-1	θmax = 30.5°, θmin = 2.8°
rotation method scans	h = −16→16
Absorption correction: numerical (X-AREA; Stoe & Cie, 2011)	k = −13→14
Tmin = 0.730, Tmax = 0.771	l = −10→10
4398 measured reflections

Refinement

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	Δρmax = 0.56 e Å^−3
1265 reflections	Δρmin = −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)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	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 (Ų)

	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)

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.