Reinvestigation of cadmium diphosphate

The crystal structure of the title compound, Cd₂P₂O₇, has been reinvestigated by means of an image-plate diffraction system. The study confirms the previously determined structure [Calvo & Au (1969). Can. J. Chem. 47, 3409–3417], but provides a less biased model and higher precision. The structure consists of alternating layers of isolated P₂O₇ groups and edge-sharing CdO₆ octa­hedra forming corrugated chains along [10]. The layers and the parallel chains inter­connect by means of corner-sharing. This room-temperature structure is actually the average of a modulated structure, which might partly rectify the unusual bond valences.

Key indicators

• Single-crystal X-ray study
• T = 292 K
• Mean [sigma](P-O) = 0.003 Å
• R factor = 0.022
• wR factor = 0.055
• Data-to-parameter ratio = 11.8

checkCIF/PLATON results

No syntax errors found



Alert level A
REFLT03_ALERT_3_A  Reflection count < 85% complete (theta max?)
           From the CIF: _diffrn_reflns_theta_max           29.07
           From the CIF: _diffrn_reflns_theta_full          29.07
           From the CIF: _reflns_number_total               1189
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         1425
           Completeness (_total/calc)             83.44%

Author Response: We planned two runs, one at phi=0 deg and one at pohi=90 deg. Unfortunately, the crystal mysteriously disappeared after the first run.

PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.83

Author Response: same answer as above!

Alert level C
PLAT155_ALERT_4_C The Triclinic Unitcell is NOT Reduced ..........          ?

   2 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: X-AREA (Stoe & Cie, 2005); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: DIRDIF (Beurskens et al., 1996); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1996) and CrystalMaker (Palmer, 2004); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003).

Cadmium diphosphate

Crystal data

Cd2(P2O7)	Z = 2
Mr = 398.74	F(000) = 364
Triclinic, P1	Dx = 4.964 (2) Mg m^−3 Dm = 4.90 Mg m^−3 Dm measured by Calvo & Au (1969)
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.6075 (13) Å	Cell parameters from 4542 reflections
b = 6.6371 (13) Å	θ = 3.1–29.4°
c = 6.7887 (14) Å	µ = 8.57 mm^−1
α = 95.82 (3)°	T = 292 K
β = 115.13 (3)°	Platelet, colourless
γ = 82.24 (3)°	0.50 × 0.40 × 0.15 mm
V = 266.75 (11) Å^3

Data collection

Stoe IPDS-2 diffractometer	1189 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	1162 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.052
Detector resolution: 6.67 pixels mm^-1	θmax = 29.1°, θmin = 3.1°
ω scans	h = −8→8
Absorption correction: integration (X-RED; Stoe & Cie, 2005)	k = −9→8
Tmin = 0.162, Tmax = 0.314	l = −9→9
2251 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.022	w = 1/[σ^2(Fo^2) + (0.0173P)^2 + 0.5407P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.055	(Δ/σ)max = 0.001
S = 1.25	Δρmax = 0.54 e Å^−3
1189 reflections	Δρmin = −0.88 e Å^−3
101 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.292 (7)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) 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, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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.

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

	x	y	z	Uiso*/Ueq
Cd1	0.27522 (4)	0.36011 (4)	0.33760 (4)	0.01039 (12)
Cd2	0.11672 (4)	0.16059 (3)	0.74836 (4)	0.00682 (12)
P1	0.36229 (15)	0.86612 (13)	0.18989 (15)	0.00487 (19)
P2	0.23622 (15)	0.65878 (12)	0.75488 (14)	0.00449 (19)
O1	0.4032 (4)	0.7487 (4)	0.9858 (4)	0.0078 (5)
O2	0.0690 (5)	0.8336 (4)	0.6354 (4)	0.0099 (5)
O3	0.6004 (4)	0.8650 (4)	0.3669 (4)	0.0082 (5)
O4	0.3913 (4)	0.5669 (4)	0.6495 (4)	0.0079 (5)
O5	0.2578 (5)	0.0810 (4)	0.1129 (4)	0.0091 (5)
O6	0.1009 (5)	0.5043 (4)	0.7858 (5)	0.0112 (5)
O7	0.2109 (4)	0.7452 (4)	0.2351 (4)	0.0096 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.00774 (18)	0.01239 (17)	0.01146 (19)	−0.00300 (11)	0.00504 (13)	−0.00500 (11)
Cd2	0.00723 (17)	0.00594 (16)	0.00851 (18)	−0.00034 (10)	0.00447 (13)	0.00074 (10)
P1	0.0038 (4)	0.0065 (4)	0.0049 (4)	−0.0010 (3)	0.0022 (3)	0.0009 (3)
P2	0.0046 (4)	0.0042 (4)	0.0053 (4)	−0.0015 (3)	0.0026 (3)	−0.0006 (3)
O1	0.0040 (12)	0.0133 (11)	0.0068 (12)	−0.0027 (9)	0.0032 (10)	−0.0026 (9)
O2	0.0108 (13)	0.0076 (11)	0.0095 (13)	0.0006 (9)	0.0030 (11)	−0.0001 (9)
O3	0.0038 (12)	0.0110 (11)	0.0081 (12)	−0.0011 (9)	0.0009 (10)	−0.0004 (9)
O4	0.0075 (12)	0.0090 (11)	0.0096 (12)	−0.0022 (9)	0.0056 (10)	−0.0007 (9)
O5	0.0110 (13)	0.0057 (10)	0.0090 (12)	0.0011 (9)	0.0030 (10)	0.0019 (8)
O6	0.0097 (13)	0.0085 (11)	0.0188 (14)	−0.0042 (9)	0.0086 (11)	0.0000 (9)
O7	0.0080 (13)	0.0116 (11)	0.0130 (13)	−0.0015 (9)	0.0069 (10)	0.0042 (9)

Geometric parameters (Å, º)

Cd1—O5	2.260 (2)	O1—O2	2.516 (4)
Cd1—O4^i	2.283 (3)	O1—O6	2.567 (4)
Cd1—O4	2.296 (3)	O1—O7	4.698 (4)
Cd1—O6^ii	2.338 (3)	O1—O3	5.052 (4)
Cd1—O3^i	2.410 (3)	O1—O5	6.831 (4)
Cd1—O7	2.648 (3)	O2—Cd2^v	2.245 (2)
Cd2—O7^ii	2.217 (3)	O2—Cd2^ii	2.364 (3)
Cd2—O2^iii	2.245 (2)	O2—O6	2.452 (4)
Cd2—O6	2.263 (2)	O2—O4	2.554 (4)
Cd2—O3^i	2.294 (3)	O3—Cd2^i	2.294 (3)
Cd2—O5^iv	2.334 (3)	O3—Cd1^i	2.410 (3)
Cd2—O2^ii	2.364 (3)	O3—O1^vi	2.448 (4)
P1—O7	1.505 (3)	O3—O5^v	2.542 (4)
P1—O3	1.521 (3)	O3—O7	2.551 (4)
P1—O5^v	1.537 (3)	O3—O5	5.764 (4)
P1—O1^vi	1.626 (3)	O4—Cd1^i	2.283 (3)
P1—P2^vi	2.9503 (16)	O4—O6	2.552 (4)
P2—O4	1.516 (3)	O5—P1^iii	1.537 (3)
P2—O2	1.520 (3)	O5—Cd2^vi	2.334 (3)
P2—O6	1.532 (3)	O5—O7	4.396 (3)
P2—O1	1.597 (3)	O6—Cd1^ii	2.338 (3)
O1—P1^iv	1.626 (3)	O7—Cd2^ii	2.217 (3)
O1—O4	2.447 (3)	O7—O1^vi	2.514 (4)
O1—O5^vii	2.506 (3)	O7—O5^v	2.555 (4)
O5—Cd1—O4^i	93.56 (10)	P1—O3—Cd1^i	119.78 (15)
O5—Cd1—O4	159.61 (9)	Cd2^i—O3—Cd1^i	106.58 (11)
O4^i—Cd1—O4	80.41 (10)	Cd2^i—O3—O1^vi	79.01 (10)
O5—Cd1—O6^ii	102.73 (10)	Cd1^i—O3—O1^vi	122.29 (12)
O4^i—Cd1—O6^ii	140.14 (10)	Cd2^i—O3—O5^v	110.18 (13)
O4—Cd1—O6^ii	94.07 (10)	Cd1^i—O3—O5^v	142.61 (13)
O5—Cd1—O3^i	87.81 (9)	O1^vi—O3—O5^v	60.26 (11)
O4^i—Cd1—O3^i	101.75 (10)	Cd2^i—O3—O7	137.85 (12)
O4—Cd1—O3^i	74.56 (9)	Cd1^i—O3—O7	87.76 (11)
O6^ii—Cd1—O3^i	114.84 (10)	O1^vi—O3—O7	60.35 (10)
O5—Cd1—O7	127.01 (9)	O5^v—O3—O7	60.23 (11)
O4^i—Cd1—O7	74.14 (9)	P1—O3—O1	95.95 (12)
O4—Cd1—O7	70.28 (9)	Cd2^i—O3—O1	145.15 (10)
O6^ii—Cd1—O7	66.95 (9)	O1^vi—O3—O1	126.09 (11)
O3^i—Cd1—O7	144.80 (8)	O5^v—O3—O1	103.87 (10)
O7^ii—Cd2—O2^iii	98.88 (10)	O7—O3—O1	67.26 (9)
O7^ii—Cd2—O6	76.13 (10)	P1—O3—O5	64.60 (10)
O2^iii—Cd2—O6	166.83 (11)	Cd2^i—O3—O5	103.49 (8)
O7^ii—Cd2—O3^i	160.31 (10)	Cd1^i—O3—O5	65.94 (6)
O2^iii—Cd2—O3^i	88.25 (10)	O1^vi—O3—O5	57.22 (9)
O6—Cd2—O3^i	92.82 (10)	O5^v—O3—O5	98.57 (10)
O7^ii—Cd2—O5^iv	87.31 (10)	O7—O3—O5	46.06 (8)
O2^iii—Cd2—O5^iv	91.72 (9)	O1—O3—O5	78.02 (6)
O6—Cd2—O5^iv	100.13 (10)	P2—O4—Cd1^i	135.22 (14)
O3^i—Cd2—O5^iv	110.93 (10)	P2—O4—Cd1	123.02 (14)
O7^ii—Cd2—O2^ii	88.90 (10)	Cd1^i—O4—Cd1	99.59 (10)
O2^iii—Cd2—O2^ii	75.37 (11)	Cd1^i—O4—O1	99.69 (11)
O6—Cd2—O2^ii	92.21 (10)	Cd1—O4—O1	160.58 (13)
O3^i—Cd2—O2^ii	75.09 (10)	Cd1^i—O4—O6	158.84 (14)
O5^iv—Cd2—O2^ii	165.82 (9)	Cd1—O4—O6	98.86 (11)
O7—P1—O3	114.94 (16)	O1—O4—O6	61.75 (11)
O7—P1—O5^v	114.27 (16)	Cd1^i—O4—O2	124.46 (11)
O3—P1—O5^v	112.48 (15)	Cd1—O4—O2	109.55 (12)
O7—P1—O1^vi	106.77 (14)	O1—O4—O2	60.35 (11)
O3—P1—O1^vi	102.09 (14)	O6—O4—O2	57.39 (11)
O5^v—P1—O1^vi	104.78 (15)	P1^iii—O5—Cd1	124.47 (16)
O7—P1—P2^vi	90.46 (11)	P1^iii—O5—Cd2^vi	122.26 (14)
O3—P1—P2^vi	125.06 (11)	Cd1—O5—Cd2^vi	112.52 (11)
O5^v—P1—P2^vi	97.26 (11)	P1^iii—O5—O7	150.57 (14)
O4—P2—O2	114.55 (16)	Cd2^vi—O5—O7	84.11 (8)
O4—P2—O6	113.72 (14)	P1^iii—O5—O3	132.13 (13)
O2—P2—O6	106.92 (16)	Cd2^vi—O5—O3	89.34 (8)
O4—P2—O1	103.60 (14)	P1^iii—O5—O1	110.41 (12)
O2—P2—O1	107.62 (14)	Cd2^vi—O5—O1	126.84 (8)
O6—P2—O1	110.26 (16)	O3—O5—O1	46.35 (4)
P2—O1—P1^iv	132.56 (17)	P2—O6—Cd2	133.13 (16)
P1^iv—O1—O4	169.57 (16)	P2—O6—Cd1^ii	108.83 (15)
P2—O1—O5^vii	115.01 (15)	Cd2—O6—Cd1^ii	109.01 (11)
O4—O1—O5^vii	140.17 (15)	Cd2—O6—O2	150.13 (15)
P1^iv—O1—O2	109.67 (14)	Cd1^ii—O6—O2	72.60 (11)
O4—O1—O2	61.93 (11)	Cd2—O6—O4	100.50 (12)
O5^vii—O1—O2	81.75 (12)	Cd1^ii—O6—O4	128.31 (14)
P1^iv—O1—O6	109.62 (14)	O2—O6—O4	61.34 (11)
O4—O1—O6	61.14 (10)	Cd2—O6—O1	132.41 (14)
O5^vii—O1—O6	113.74 (13)	Cd1^ii—O6—O1	117.66 (12)
O2—O1—O6	57.67 (11)	O2—O6—O1	60.11 (11)
P1^iv—O1—O7	145.57 (13)	O4—O6—O1	57.11 (10)
O5^vii—O1—O7	110.26 (11)	P1—O7—Cd2^ii	130.49 (15)
O6—O1—O7	71.23 (9)	Cd2^ii—O7—O1^vi	141.04 (14)
P2—O1—O3	66.36 (10)	Cd2^ii—O7—O3	140.33 (13)
P1^iv—O1—O3	142.18 (12)	O1^vi—O7—O3	57.78 (10)
O5^vii—O1—O3	109.41 (10)	Cd2^ii—O7—O5^v	97.56 (12)
O2—O1—O3	65.74 (9)	O1^vi—O7—O5^v	59.24 (10)
O6—O1—O3	99.06 (10)	O3—O7—O5^v	59.70 (11)
P1^iv—O1—O5	159.01 (11)	P1—O7—Cd1	129.13 (15)
O5^vii—O1—O5	145.04 (12)	Cd2^ii—O7—Cd1	100.32 (10)
O2—O1—O5	63.35 (8)	O1^vi—O7—Cd1	104.30 (11)
O6—O1—O5	49.48 (8)	O3—O7—Cd1	106.39 (12)
O3—O1—O5	55.63 (5)	O5^v—O7—Cd1	161.96 (13)
P2—O2—Cd2^v	122.45 (15)	P1—O7—O5	119.05 (13)
P2—O2—Cd2^ii	123.45 (14)	Cd2^ii—O7—O5	107.18 (9)
Cd2^v—O2—Cd2^ii	104.63 (11)	O1^vi—O7—O5	85.56 (9)
Cd2^v—O2—O6	139.52 (14)	O3—O7—O5	109.24 (11)
Cd2^ii—O2—O6	115.07 (12)	O5^v—O7—O5	144.08 (13)
Cd2^v—O2—O1	85.91 (11)	P1—O7—O1	111.11 (13)
Cd2^ii—O2—O1	153.02 (13)	Cd2^ii—O7—O1	77.60 (8)
O6—O2—O1	62.22 (11)	O1^vi—O7—O1	138.50 (12)
Cd2^v—O2—O4	123.18 (13)	O3—O7—O1	82.68 (10)
Cd2^ii—O2—O4	96.54 (11)	O5^v—O7—O1	113.42 (10)
O6—O2—O4	61.27 (10)	Cd1—O7—O1	73.11 (7)
O1—O2—O4	57.72 (10)	O5—O7—O1	97.32 (8)
P1—O3—Cd2^i	116.43 (15)

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