Low-energy contamination of Mo microsource X-ray radiation: analysis and solution of the problem

In recent years, microsource sealed tubes in combination with multilayer optics have been adopted in many crystallography laboratories for very low power X-ray generation, monochromatization and high-brilliance microfocusing. All these factors allow high-performance experiments on a laboratory scale. However, a fundamental defect of this technology has been discovered, namely a significant contamination of the characteristic radiation by low-energy photons. Some simple experiments are reported, showing that the contamination can significantly reduce the accuracy of the measured intensities, especially when Mo Kα radiation is used. A simple and economic solution to the problem is proposed: an aluminium filter approximately 100 µm thick, which efficiently removes the low-energy contaminant photons.

Computing details

Data collection: CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.36 (release 02-08-2010 CrysAlis171 .NET) (compiled Aug 2 2010,13:00:58) for (IIA); CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.41 (release 13-09-2010 CrysAlis171 .NET) (compiled Sep 13 2010,14:28:38) for (IIC). Cell refinement: CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.36 (release 02-08-2010 CrysAlis171 .NET) (compiled Aug 2 2010,13:00:58) for (IIA); CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.41 (release 13-09-2010 CrysAlis171 .NET) (compiled Sep 13 2010,14:28:38) for (IIC). Data reduction: CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.36 (release 02-08-2010 CrysAlis171 .NET) (compiled Aug 2 2010,13:00:58) for (IIA); CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.41 (release 13-09-2010 CrysAlis171 .NET) (compiled Sep 13 2010,14:28:38) for (IIC). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) for (IA), (IB), (IC), (ID), (IE); Volkov et al., (2006) for (IIA), (IIB), (IIC). Molecular graphics: Volkov et al., (2006) for (IIA), (IIB), (IIC). Software used to prepare material for publication: Volkov et al., (2006) for (IIA), (IIB), (IIC).

(IA)

Crystal data

C6H24N8NiO6	V = 773.07 (5) Å^3
Mr = 363.04	Z = 2
?, ?	F(000) = 384
a = 8.8647 (3) Å	Dx = 1.56 Mg m^−3
b = 8.8647 (3) Å	Mo Kα radiation, λ = 0.71073 Å
c = 11.3595 (4) Å	µ = 1.30 mm^−1
α = 90°	T = 293 K
β = 90°	0.18 × 0.13 × 0.05 mm
γ = 120°

Data collection

Graphite monochromator	Rint = 0.049
Absorption correction: multi-scan ?	θmax = 32.8°, θmin = 3.2°
Tmin = 0.588, Tmax = 1.000	h = −13→13
16785 measured reflections	k = −13→12
934 independent reflections	l = −17→16
819 reflections with I > 2σ(I)

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.027	w = 1/[σ^2(Fo^2) + (0.P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.040	(Δ/σ)max < 0.001
S = 2.31	Δρmax = 0.22 e Å^−3
934 reflections	Δρmin = −0.17 e Å^−3
34 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.039 (2)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.01 (2)

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
Ni1	0.3333	0.6667	0.75	0.03255 (12)
N1	0.54300 (13)	0.85974 (13)	0.64801 (10)	0.0435 (3)
H1A	0.5239	0.8332	0.571	0.052*
H1B	0.5523	0.9645	0.6593	0.052*
C1	0.70356 (15)	0.8641 (2)	0.68573 (12)	0.0562 (4)
H1C	0.8034	0.9751	0.6641	0.067*
H1D	0.7136	0.7729	0.6457	0.067*
N2	0.3333	0.6667	0.38941 (14)	0.0469 (4)
O1	0.48346 (13)	0.69236 (13)	0.39179 (10)	0.0762 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.02339 (13)	0.02339 (13)	0.0509 (2)	0.01169 (6)	0	0
N1	0.0334 (7)	0.0331 (6)	0.0599 (7)	0.0135 (5)	0.0014 (6)	0.0037 (5)
C1	0.0292 (6)	0.0438 (10)	0.0900 (9)	0.0141 (9)	0.0103 (6)	0.0098 (10)
N2	0.0473 (6)	0.0473 (6)	0.0461 (9)	0.0236 (3)	0	0
O1	0.0451 (6)	0.0791 (9)	0.1083 (9)	0.0339 (6)	0.0006 (6)	−0.0054 (7)

Geometric parameters (Å, º)

Ni1—N1^i	2.1319 (10)	N1—H1B	0.9
Ni1—N1^ii	2.1319 (10)	C1—C1^iv	1.476 (3)
Ni1—N1^iii	2.1319 (10)	C1—H1C	0.97
Ni1—N1	2.1319 (10)	C1—H1D	0.97
Ni1—N1^iv	2.1319 (10)	N2—O1^ii	1.2331 (10)
Ni1—N1^v	2.1319 (10)	N2—O1^v	1.2331 (10)
N1—C1	1.4682 (15)	N2—O1	1.2331 (10)
N1—H1A	0.9
N1^i—Ni1—N1^ii	81.95 (6)	C1—N1—Ni1	107.88 (8)
N1^i—Ni1—N1^iii	93.27 (4)	C1—N1—H1A	110.1
N1^ii—Ni1—N1^iii	91.91 (6)	Ni1—N1—H1A	110.1
N1^i—Ni1—N1	91.91 (6)	C1—N1—H1B	110.1
N1^ii—Ni1—N1	93.27 (4)	Ni1—N1—H1B	110.1
N1^iii—Ni1—N1	173.15 (6)	H1A—N1—H1B	108.4
N1^i—Ni1—N1^iv	93.27 (4)	N1—C1—C1^iv	110.89 (10)
N1^ii—Ni1—N1^iv	173.15 (6)	N1—C1—H1C	109.5
N1^iii—Ni1—N1^iv	93.27 (4)	C1^iv—C1—H1C	109.5
N1—Ni1—N1^iv	81.95 (6)	N1—C1—H1D	109.5
N1^i—Ni1—N1^v	173.15 (6)	C1^iv—C1—H1D	109.5
N1^ii—Ni1—N1^v	93.27 (4)	H1C—C1—H1D	108
N1^iii—Ni1—N1^v	81.95 (6)	O1^ii—N2—O1^v	119.952 (8)
N1—Ni1—N1^v	93.27 (4)	O1^ii—N2—O1	119.952 (8)
N1^iv—Ni1—N1^v	91.91 (6)	O1^v—N2—O1	119.952 (8)
N1^i—Ni1—N1—C1	106.18 (10)	N1^iv—Ni1—N1—C1	13.15 (8)
N1^ii—Ni1—N1—C1	−171.78 (9)	N1^v—Ni1—N1—C1	−78.32 (11)
N1^iii—Ni1—N1—C1	−32.83 (9)	Ni1—N1—C1—C1^iv	−37.9 (2)

Symmetry codes: (i) −x+y, y, −z+3/2; (ii) −y+1, x−y+1, z; (iii) −y+1, −x+1, −z+3/2; (iv) x, x−y+1, −z+3/2; (v) −x+y, −x+1, z.

(IB)

Crystal data

C6H24N8NiO6	V = 773.07 (5) Å^3
Mr = 363.04	Z = 2
?, ?	F(000) = 336
a = 8.8647 (3) Å	Dx = 1.456 Mg m^−3
b = 8.8647 (3) Å	Mo Kα radiation, λ = 0.71073 Å
c = 11.3595 (4) Å	µ = 1.29 mm^−1
α = 90°	T = 293 K
β = 90°	0.18 × 0.13 × 0.05 mm
γ = 120°

Data collection

Graphite monochromator	Rint = 0.045
Absorption correction: multi-scan ?	θmax = 32.8°, θmin = 3.2°
Tmin = 0.853, Tmax = 1.000	h = −13→13
16770 measured reflections	k = −13→13
935 independent reflections	l = −16→17
838 reflections with I > 2σ(I)

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.03	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.125	(Δ/σ)max = 0.005
S = 1.02	Δρmax = 0.23 e Å^−3
935 reflections	Δρmin = −0.19 e Å^−3
34 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.060 (12)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.02 (5)

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
Ni1	0.3333	0.6667	0.75	0.0326 (2)
N1	0.5430 (2)	0.8602 (2)	0.64807 (19)	0.0453 (4)
H1A	0.5231	0.835	0.5709	0.054*
H1B	0.5536	0.9654	0.6606	0.054*
C1	0.7040 (3)	0.8618 (5)	0.6848 (2)	0.0547 (6)
H1C	0.8051	0.9705	0.6611	0.066*
H1D	0.7102	0.767	0.6468	0.066*
N2	0.3333	0.6667	0.3897 (3)	0.0472 (7)
O1	0.4833 (3)	0.6930 (3)	0.3927 (3)	0.0764 (7)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0237 (2)	0.0237 (2)	0.0504 (3)	0.01183 (11)	0	0
N1	0.0329 (9)	0.0320 (8)	0.0656 (10)	0.0121 (7)	0.0050 (8)	0.0058 (8)
C1	0.0293 (8)	0.0431 (12)	0.0876 (15)	0.0149 (10)	0.0105 (9)	0.0060 (15)
N2	0.0471 (10)	0.0471 (10)	0.0475 (13)	0.0235 (5)	0	0
O1	0.0477 (10)	0.0746 (15)	0.1079 (16)	0.0314 (9)	0.0032 (11)	−0.0014 (11)

Geometric parameters (Å, º)

Ni1—N1^i	2.1332 (19)	N1—H1B	0.9
Ni1—N1^ii	2.1332 (19)	C1—C1^v	1.491 (5)
Ni1—N1	2.1332 (19)	C1—H1C	0.97
Ni1—N1^iii	2.1332 (19)	C1—H1D	0.97
Ni1—N1^iv	2.1332 (19)	N2—O1^i	1.230 (2)
Ni1—N1^v	2.1332 (19)	N2—O1^iv	1.230 (2)
N1—C1	1.481 (3)	N2—O1	1.230 (2)
N1—H1A	0.9
N1^i—Ni1—N1^ii	82.02 (11)	C1—N1—Ni1	107.61 (15)
N1^i—Ni1—N1	93.33 (8)	C1—N1—H1A	110.2
N1^ii—Ni1—N1	91.68 (11)	Ni1—N1—H1A	110.2
N1^i—Ni1—N1^iii	91.68 (11)	C1—N1—H1B	110.2
N1^ii—Ni1—N1^iii	93.33 (8)	Ni1—N1—H1B	110.2
N1—Ni1—N1^iii	173.36 (10)	H1A—N1—H1B	108.5
N1^i—Ni1—N1^iv	93.33 (8)	N1—C1—C1^v	109.57 (19)
N1^ii—Ni1—N1^iv	173.36 (10)	N1—C1—H1C	109.8
N1—Ni1—N1^iv	93.33 (8)	C1^v—C1—H1C	109.8
N1^iii—Ni1—N1^iv	82.02 (11)	N1—C1—H1D	109.8
N1^i—Ni1—N1^v	173.36 (10)	C1^v—C1—H1D	109.8
N1^ii—Ni1—N1^v	93.33 (8)	H1C—C1—H1D	108.2
N1—Ni1—N1^v	82.02 (11)	O1^i—N2—O1^iv	119.92 (2)
N1^iii—Ni1—N1^v	93.33 (8)	O1^i—N2—O1	119.92 (2)
N1^iv—Ni1—N1^v	91.68 (11)	O1^iv—N2—O1	119.92 (2)
N1^i—Ni1—N1—C1	−170.64 (17)	N1^iv—Ni1—N1—C1	−77.1 (2)
N1^ii—Ni1—N1—C1	107.25 (19)	N1^v—Ni1—N1—C1	14.13 (14)
N1^iii—Ni1—N1—C1	−31.73 (17)	Ni1—N1—C1—C1^v	−40.5 (4)

Symmetry codes: (i) −y+1, x−y+1, z; (ii) −x+y, y, −z+3/2; (iii) −y+1, −x+1, −z+3/2; (iv) −x+y, −x+1, z; (v) x, x−y+1, −z+3/2.

(IC)

Crystal data

C6H24N8NiO6	V = 2226.0 (18) Å^3
Mr = 363.04	Z = 6
?, ?	F(000) = 1152
a = 8.806 (5) Å	Dx = 1.625 Mg m^−3
b = 8.806 (5) Å	Mo Kα radiation, λ = 0.71069 Å
c = 33.147 (5) Å	µ = 1.35 mm^−1
α = 90.000 (5)°	T = 100 K
β = 90.000 (5)°	0.18 × 0.13 × 0.05 mm
γ = 120.000 (5)°

Data collection

Graphite monochromator	Rint = 0.031
Absorption correction: multi-scan ?	θmax = 28.9°, θmin = 2.9°
Tmin = 0.818, Tmax = 1.000	h = −10→11
10049 measured reflections	k = −10→11
1810 independent reflections	l = −44→44
1730 reflections with I > 2σ(I)

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	All H-atom parameters refined
wR(F^2) = 0.105	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.90	(Δ/σ)max = 0.16
1810 reflections	Δρmax = 0.32 e Å^−3
144 parameters	Δρmin = −0.54 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (2)

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
Ni	0.35901 (2)	0.71802 (5)	0.25	0.01063 (15)
N1A	0.1772 (3)	0.7343 (3)	0.21035 (6)	0.0152 (4)
N1B	0.5806 (3)	0.9118 (3)	0.21777 (6)	0.0152 (4)
N1C	0.3580 (3)	0.5069 (3)	0.21789 (6)	0.0153 (4)
C1A	0.1686 (4)	0.8930 (4)	0.22104 (7)	0.0175 (5)
C1B	0.7368 (3)	0.9098 (4)	0.23315 (7)	0.0169 (5)
C1C	0.1933 (3)	0.3451 (3)	0.22779 (7)	0.0168 (5)
H1A	0.218 (4)	0.746 (4)	0.1845 (9)	0.027 (8)*
H2A	0.074 (5)	0.643 (5)	0.2116 (8)	0.019 (7)*
H1B	0.569 (4)	0.891 (4)	0.1913 (9)	0.025 (8)*
H2B	0.585 (4)	1.017 (4)	0.2206 (7)	0.009 (6)*
H1C	0.365 (4)	0.520 (4)	0.1903 (8)	0.016 (7)*
H2C	0.454 (5)	0.494 (4)	0.2259 (7)	0.023 (8)*
H3A	0.062 (4)	0.884 (4)	0.2106 (7)	0.008 (6)*
H4A	0.268 (4)	0.987 (4)	0.2099 (7)	0.007 (6)*
H3B	0.736 (4)	0.810 (5)	0.2225 (8)	0.017 (8)*
H4B	0.853 (4)	1.022 (4)	0.2259 (8)	0.020 (7)*
H3C	0.197 (5)	0.244 (5)	0.2218 (9)	0.035 (10)*
H4C	0.098 (5)	0.349 (5)	0.2140 (10)	0.034 (9)*
N2	0.6778 (3)	0.3872 (2)	0.29595 (6)	0.0151 (4)
O1A	0.8039 (3)	0.5390 (2)	0.29884 (5)	0.0250 (4)
O1B	0.7013 (3)	0.2583 (3)	0.29686 (5)	0.0241 (4)
O1C	0.5247 (2)	0.3625 (3)	0.29349 (5)	0.0230 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.00887 (18)	0.0088 (2)	0.0142 (2)	0.00441 (11)	0.00059 (12)	0
N1A	0.0131 (10)	0.0141 (10)	0.0202 (9)	0.0081 (9)	−0.0010 (8)	0.0003 (8)
N1B	0.0138 (10)	0.0117 (10)	0.0181 (9)	0.0050 (8)	0.0024 (8)	0.0021 (8)
N1C	0.0135 (9)	0.0130 (10)	0.0213 (9)	0.0080 (8)	0.0005 (8)	−0.0003 (8)
C1A	0.0151 (13)	0.0144 (12)	0.0256 (11)	0.0093 (10)	−0.0004 (9)	0.0017 (9)
C1B	0.0113 (11)	0.0124 (12)	0.0263 (11)	0.0055 (10)	0.0040 (9)	0.0000 (9)
C1C	0.0130 (12)	0.0106 (11)	0.0251 (11)	0.0046 (10)	−0.0008 (9)	−0.0035 (9)
N2	0.0153 (10)	0.0160 (9)	0.0138 (9)	0.0076 (8)	0.0019 (6)	0.0011 (6)
O1A	0.0181 (10)	0.0159 (9)	0.0340 (9)	0.0033 (8)	0.0045 (7)	0.0026 (7)
O1B	0.0254 (11)	0.0207 (10)	0.0312 (9)	0.0154 (9)	−0.0004 (7)	−0.0010 (7)
O1C	0.0152 (9)	0.0265 (10)	0.0309 (9)	0.0132 (8)	−0.0023 (7)	0.0000 (8)

Geometric parameters (Å, º)

Ni—N1B^i	2.128 (2)	N1C—C1C	1.475 (3)
Ni—N1B	2.128 (2)	C1A—C1B^i	1.524 (3)
Ni—N1A	2.131 (2)	C1B—C1A^i	1.524 (3)
Ni—N1A^i	2.131 (2)	C1C—C1C^i	1.518 (5)
Ni—N1C^i	2.138 (2)	N2—O1A	1.243 (3)
Ni—N1C	2.138 (2)	N2—O1B	1.251 (3)
N1A—C1A	1.479 (3)	N2—O1C	1.256 (3)
N1B—C1B	1.475 (3)
N1B^i—Ni—N1B	92.07 (12)	N1A—Ni—N1C	94.30 (8)
N1B^i—Ni—N1A	82.19 (8)	N1A^i—Ni—N1C	90.74 (9)
N1B—Ni—N1A	93.14 (9)	N1C^i—Ni—N1C	82.32 (11)
N1B^i—Ni—N1A^i	93.15 (9)	C1A—N1A—Ni	108.11 (15)
N1B—Ni—N1A^i	82.19 (8)	C1B—N1B—Ni	107.67 (14)
N1A—Ni—N1A^i	173.31 (12)	C1C—N1C—Ni	107.70 (15)
N1B^i—Ni—N1C^i	92.90 (8)	N1A—C1A—C1B^i	108.6 (2)
N1B—Ni—N1C^i	174.06 (9)	N1B—C1B—C1A^i	108.9 (2)
N1A—Ni—N1C^i	90.74 (9)	N1C—C1C—C1C^i	109.66 (16)
N1A^i—Ni—N1C^i	94.30 (8)	O1A—N2—O1B	120.6 (2)
N1B^i—Ni—N1C	174.06 (9)	O1A—N2—O1C	119.7 (2)
N1B—Ni—N1C	92.90 (8)	O1B—N2—O1C	119.6 (2)

Symmetry code: (i) −x+y, y, −z+1/2.

(ID)

Crystal data

C6H24N8NiO6	V = 2226.0 (18) Å^3
Mr = 363.04	Z = 6
?, ?	F(000) = 1152
a = 8.806 (5) Å	Dx = 1.625 Mg m^−3
b = 8.806 (5) Å	Mo Kα radiation, λ = 0.71069 Å
c = 33.147 (5) Å	µ = 1.35 mm^−1
α = 90.000 (5)°	T = 100 K
β = 90.000 (5)°	0.18 × 0.13 × 0.05 mm
γ = 120.000 (5)°

Data collection

Graphite monochromator	Rint = 0.030
Absorption correction: multi-scan ?	θmax = 28.9°, θmin = 2.9°
Tmin = 0.756, Tmax = 1.000	h = −10→11
10038 measured reflections	k = −10→11
1808 independent reflections	l = −44→44
1739 reflections with I > 2σ(I)

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.031	H-atom parameters constrained
wR(F^2) = 0.117	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max = 0.189
1808 reflections	Δρmax = 0.36 e Å^−3
144 parameters	Δρmin = −0.54 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.02 (2)

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
Ni	0.35906 (3)	0.71813 (5)	0.25	0.01059 (17)
N1A	0.1773 (3)	0.7347 (3)	0.21034 (7)	0.0154 (4)
N1B	0.5808 (3)	0.9119 (3)	0.21780 (7)	0.0145 (5)
N1C	0.3582 (3)	0.5072 (3)	0.21782 (7)	0.0152 (4)
C1A	0.1679 (4)	0.8923 (4)	0.22103 (8)	0.0166 (5)
C1B	0.7367 (4)	0.9109 (4)	0.23300 (8)	0.0177 (6)
C1C	0.1933 (4)	0.3449 (4)	0.22776 (8)	0.0158 (5)
H1A	0.213 (6)	0.734 (6)	0.1848 (12)	0.049 (12)*
H2A	0.065 (5)	0.643 (6)	0.2123 (9)	0.022 (9)*
H1B	0.572 (5)	0.896 (5)	0.1921 (10)	0.030 (10)*
H2B	0.594 (4)	1.016 (4)	0.2206 (8)	0.003 (6)*
H1C	0.368 (4)	0.517 (4)	0.1914 (8)	0.007 (7)*
H2C	0.451 (6)	0.498 (6)	0.2258 (10)	0.038 (11)*
H3A	0.062 (4)	0.884 (4)	0.2101 (8)	0.003 (6)*
H4A	0.275 (5)	0.988 (5)	0.2103 (9)	0.015 (8)*
H3B	0.727 (5)	0.799 (5)	0.2223 (9)	0.019 (9)*
H4B	0.852 (5)	1.016 (5)	0.2264 (9)	0.024 (9)*
H3C	0.202 (4)	0.251 (4)	0.2217 (8)	0.006 (7)*
H4C	0.094 (6)	0.353 (6)	0.2140 (11)	0.034 (10)*
N2	0.6775 (3)	0.3871 (3)	0.29594 (7)	0.0153 (4)
O1A	0.8040 (3)	0.5392 (3)	0.29893 (6)	0.0239 (5)
O1B	0.7014 (3)	0.2585 (3)	0.29689 (6)	0.0235 (5)
O1C	0.5239 (3)	0.3622 (3)	0.29357 (6)	0.0234 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.0087 (2)	0.0089 (2)	0.0142 (2)	0.00445 (12)	0.00064 (13)	0
N1A	0.0143 (12)	0.0145 (11)	0.0195 (10)	0.0088 (10)	−0.0011 (9)	−0.0006 (8)
N1B	0.0135 (11)	0.0114 (11)	0.0173 (10)	0.0052 (9)	0.0023 (8)	0.0015 (8)
N1C	0.0140 (11)	0.0107 (11)	0.0211 (10)	0.0065 (9)	0.0025 (9)	0.0001 (9)
C1A	0.0160 (14)	0.0114 (13)	0.0260 (13)	0.0095 (10)	−0.0017 (11)	0.0010 (10)
C1B	0.0138 (13)	0.0131 (13)	0.0249 (12)	0.0057 (11)	0.0028 (10)	−0.0005 (10)
C1C	0.0128 (13)	0.0107 (12)	0.0249 (13)	0.0067 (11)	0.0000 (10)	−0.0030 (10)
N2	0.0168 (11)	0.0159 (10)	0.0137 (10)	0.0085 (9)	0.0011 (7)	0.0011 (7)
O1A	0.0172 (11)	0.0155 (10)	0.0331 (10)	0.0037 (9)	0.0045 (8)	0.0029 (8)
O1B	0.0248 (12)	0.0175 (11)	0.0309 (10)	0.0128 (10)	−0.0004 (8)	−0.0022 (8)
O1C	0.0156 (10)	0.0270 (11)	0.0308 (10)	0.0132 (9)	−0.0023 (8)	−0.0002 (9)

Geometric parameters (Å, º)

Ni—N1B^i	2.129 (3)	N1C—C1C	1.478 (4)
Ni—N1B	2.129 (3)	C1A—C1B^i	1.531 (4)
Ni—N1A	2.132 (2)	C1B—C1A^i	1.531 (4)
Ni—N1A^i	2.132 (2)	C1C—C1C^i	1.520 (5)
Ni—N1C^i	2.138 (2)	N2—O1B	1.251 (3)
Ni—N1C	2.138 (2)	N2—O1A	1.246 (3)
N1A—C1A	1.474 (3)	N2—O1C	1.260 (3)
N1B—C1B	1.466 (4)
N1B^i—Ni—N1B	92.06 (13)	N1A—Ni—N1C	94.31 (9)
N1B^i—Ni—N1A	82.10 (9)	N1A^i—Ni—N1C	90.81 (10)
N1B—Ni—N1A	93.15 (10)	N1C^i—Ni—N1C	82.45 (13)
N1B^i—Ni—N1A^i	93.15 (10)	C1A—N1A—Ni	108.29 (16)
N1B—Ni—N1A^i	82.11 (9)	C1B—N1B—Ni	108.00 (16)
N1A—Ni—N1A^i	173.20 (13)	C1C—N1C—Ni	107.68 (16)
N1B^i—Ni—N1C^i	92.85 (9)	N1A—C1A—C1B^i	108.9 (2)
N1B—Ni—N1C^i	174.07 (10)	N1B—C1B—C1A^i	109.0 (2)
N1A—Ni—N1C^i	90.81 (10)	N1C—C1C—C1C^i	109.68 (18)
N1A^i—Ni—N1C^i	94.31 (9)	O1B—N2—O1A	120.4 (2)
N1B^i—Ni—N1C	174.07 (10)	O1B—N2—O1C	119.7 (2)
N1B—Ni—N1C	92.85 (9)	O1A—N2—O1C	119.8 (2)

Symmetry code: (i) −x+y, y, −z+1/2.

(IE)

Crystal data

C6H24N8NiO6	V = 773.07 (5) Å^3
Mr = 363.04	Z = 2
?, ?	F(000) = 384
a = 8.8647 (3) Å	Dx = 1.56 Mg m^−3
b = 8.8647 (3) Å	Mo Kα radiation, λ = 0.71073 Å
c = 11.3595 (4) Å	µ = 1.30 mm^−1
α = 90°	T = 293 K
β = 90°	0.18 × 0.13 × 0.05 mm
γ = 120°

Data collection

Graphite monochromator	Rint = 0.069
Absorption correction: multi-scan ?	θmax = 32.5°, θmin = 2.7°
Tmin = 0.831, Tmax = 1.000	h = −13→13
16710 measured reflections	k = −13→13
940 independent reflections	l = −17→16
738 reflections with I > 2σ(I)

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.044	w = 1/[σ^2(Fo^2) + (0.P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.057	(Δ/σ)max < 0.001
S = 2.26	Δρmax = 0.61 e Å^−3
940 reflections	Δρmin = −0.45 e Å^−3
34 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0338 (19)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.05 (4)

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
Ni1	0.3333	0.6667	0.75	0.03467 (19)
N1	0.5431 (2)	0.8599 (2)	0.64814 (16)	0.0453 (5)
H1A	0.5242	0.8334	0.5711	0.054*
H1B	0.5523	0.9646	0.6594	0.054*
C1	0.7038 (2)	0.8644 (4)	0.68596 (18)	0.0580 (6)
H1C	0.7141	0.7734	0.6458	0.07*
H1D	0.8035	0.9756	0.6645	0.07*
N2	0.3333	0.6667	0.3894 (2)	0.0480 (7)
O1	0.4835 (2)	0.6923 (2)	0.39163 (16)	0.0788 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0251 (2)	0.0251 (2)	0.0538 (4)	0.01254 (11)	0	0
N1	0.0354 (11)	0.0349 (11)	0.0619 (11)	0.0148 (9)	0.0007 (9)	0.0040 (9)
C1	0.0300 (11)	0.0475 (17)	0.0913 (16)	0.0154 (15)	0.0114 (10)	0.0139 (17)
N2	0.0493 (11)	0.0493 (11)	0.0454 (16)	0.0246 (5)	0	0
O1	0.0473 (11)	0.0826 (14)	0.1115 (15)	0.0362 (10)	0.0007 (10)	−0.0057 (11)

Geometric parameters (Å, º)

Ni1—N1^i	2.1321 (16)	N1—H1B	0.9
Ni1—N1^ii	2.1321 (16)	C1—C1^iv	1.472 (4)
Ni1—N1^iii	2.1321 (16)	C1—H1C	0.97
Ni1—N1	2.1321 (16)	C1—H1D	0.97
Ni1—N1^iv	2.1321 (16)	N2—O1^ii	1.2333 (15)
Ni1—N1^v	2.1321 (16)	N2—O1^v	1.2333 (15)
N1—C1	1.468 (2)	N2—O1	1.2333 (15)
N1—H1A	0.9
N1^i—Ni1—N1^ii	81.87 (10)	C1—N1—Ni1	107.92 (13)
N1^i—Ni1—N1^iii	93.34 (7)	C1—N1—H1A	110.1
N1^ii—Ni1—N1^iii	91.84 (10)	Ni1—N1—H1A	110.1
N1^i—Ni1—N1	91.84 (10)	C1—N1—H1B	110.1
N1^ii—Ni1—N1	93.34 (7)	Ni1—N1—H1B	110.1
N1^iii—Ni1—N1	173.14 (10)	H1A—N1—H1B	108.4
N1^i—Ni1—N1^iv	93.34 (7)	C1^iv—C1—N1	110.99 (16)
N1^ii—Ni1—N1^iv	173.14 (10)	C1^iv—C1—H1C	109.4
N1^iii—Ni1—N1^iv	93.34 (7)	N1—C1—H1C	109.4
N1—Ni1—N1^iv	81.87 (10)	C1^iv—C1—H1D	109.4
N1^i—Ni1—N1^v	173.14 (10)	N1—C1—H1D	109.4
N1^ii—Ni1—N1^v	93.34 (7)	H1C—C1—H1D	108
N1^iii—Ni1—N1^v	81.87 (10)	O1^ii—N2—O1^v	119.957 (13)
N1—Ni1—N1^v	93.34 (7)	O1^ii—N2—O1	119.957 (13)
N1^iv—Ni1—N1^v	91.84 (10)	O1^v—N2—O1	119.957 (12)
N1^i—Ni1—N1—C1	106.17 (17)	N1^v—Ni1—N1—C1	−78.33 (19)
N1^ii—Ni1—N1—C1	−171.87 (15)	Ni1—N1—C1—C1^iv	−37.8 (3)
N1^iv—Ni1—N1—C1	13.06 (13)

Symmetry codes: (i) −x+y, y, −z+3/2; (ii) −y+1, x−y+1, z; (iii) −y+1, −x+1, −z+3/2; (iv) x, x−y+1, −z+3/2; (v) −x+y, −x+1, z.

(IIA)

Crystal data

C4H7NO4	F(000) = 560
Mr = 133.11	Dx = 1.712 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.805 (9) Å	Cell parameters from 7916 reflections
b = 5.6535 (18) Å	θ = 3.5–52.7°
c = 12.126 (9) Å	µ = 0.16 mm^−1
β = 107.55 (4)°	T = 100 K
V = 1033.1 (10) Å^3	0.36 × 0.34 × 0.10 mm
Z = 8

Data collection

SuperNova, Single source at offset), Eos diffractometer	2964 independent reflections
Graphite monochromator	2481 reflections with I > 2σ(I)
Detector resolution: 16.0965 pixels mm^-1	Rint = 0.017
ω and π scans	θmax = 53.0°, θmin = 3.5°
Absorption correction: multi-scan CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.36 (release 02-08-2010 CrysAlis171 .NET) (compiled Aug 2 2010,13:00:58) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −26→24
Tmin = 0.877, Tmax = 1	k = −8→8
7082 measured reflections	l = −11→26

Refinement

Refinement on F	89 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.03	w1 = 1/[s^2(Fo)]
wR(F^2) = 0.036	(Δ/σ)max = 0.00006
S = 2.96	Δρmax = 0.36 e Å^−3
3673 reflections	Δρmin = −0.44 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq
O(1)	0.24415 (3)	0.89994 (7)	0.38196 (3)	0.01
O(2)	0.31280 (3)	1.32896 (7)	0.42008 (3)	0.009
O(3)	0.18011 (3)	1.48928 (7)	0.33356 (3)	0.009
O(4)	0.11015 (3)	1.05174 (8)	0.28987 (4)	0.014
N(1)	0.07154 (3)	1.48320 (8)	0.10484 (3)	0.009
C(1)	0.23245 (3)	1.31820 (9)	0.36888 (4)	0.007
C(2)	0.18827 (3)	1.07220 (9)	0.34244 (4)	0.008
C(3)	0.04222 (4)	1.27354 (10)	0.02931 (4)	0.01
C(4)	−0.00326 (4)	1.64935 (10)	0.09557 (4)	0.009
H(7)	0.214342	0.73048	0.365033	0.025 (3)*
H(1)	−0.006838	1.185105	0.061627	0.037 (3)*
H(2)	0.022813	1.8014	0.150603	0.031 (3)*
H(3)	−0.053451	1.555922	0.12371	0.023 (2)*
H(4)	0.120895	1.578402	0.083076	0.025 (3)*
H(5)	0.099418	1.158186	0.040151	0.028 (3)*
H(6)	0.09742	1.42835	0.190766	0.020 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00763 (17)	0.00611 (17)	0.01363 (13)	−0.00015 (12)	0.00131 (12)	0.00036 (11)
O(2)	0.00689 (17)	0.00720 (17)	0.01231 (13)	−0.00051 (12)	0.00098 (12)	−0.00070 (11)
O(3)	0.00919 (17)	0.00691 (16)	0.01020 (12)	0.00124 (12)	0.00141 (12)	0.00086 (11)
O(4)	0.00749 (18)	0.00967 (19)	0.02067 (17)	−0.00089 (13)	−0.00196 (14)	−0.00175 (14)
N(1)	0.00638 (18)	0.00945 (19)	0.00816 (13)	−0.00015 (13)	−0.00012 (12)	0.00029 (12)
C(1)	0.0069 (2)	0.00530 (19)	0.00804 (13)	0.00018 (14)	0.00116 (13)	−0.00002 (12)
C(2)	0.0070 (2)	0.0066 (2)	0.00911 (14)	−0.00022 (14)	0.00115 (14)	−0.00043 (13)
C(3)	0.0093 (2)	0.0075 (2)	0.01185 (16)	0.00132 (15)	0.00069 (15)	0.00033 (14)
C(4)	0.0088 (2)	0.0098 (2)	0.00930 (15)	0.00011 (16)	0.00202 (15)	−0.00193 (14)

Geometric parameters (Å, º)

O1—C2	1.3049 (12)	C1—C2	1.5458 (14)
O2—C1	1.2355 (11)	C2—O4	1.2122 (13)
O3—C1	1.2608 (11)	N1—C4	1.4874 (13)
O2—C1—O3	127.01 (3)	O4—C2—C1	121.31 (2)
O2—C1—C2	118.69 (3)	O1—C2—C1	112.45 (3)
O3—C1—C2	114.25 (2)	C4—N1—C3	111.36 (3)
O4—C2—O1	126.24 (3)

(IIB)

Crystal data

C8H14N2O8	V = 1037.66 (1) Å^3
Mr = 266.21	Z = 4
?, ?	F(000) = 560
a = 15.82050 (11) Å	Dx = 1.702 Mg m^−3
b = 5.68202 (3) Å	Mo Kα radiation, λ = 0.71073 Å
c = 12.09246 (8) Å	µ = 0.15 mm^−1
α = 90°	T = 100 K
β = 107.3327 (8)°	0.35 × 0.13 × 0.12 mm
γ = 90°

Data collection

SuperNova, Single source at offset), Eos diffractometer	4099 independent reflections
Graphite monochromator	3811 reflections with I > 2σ(I)
Detector resolution: 16.0965 pixels mm^-1	Rint = 0.018
ω and π scans	θmax = 44.4°, θmin = 3.5°
Absorption correction: multi-scan CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.41 (release 13-09-2010 CrysAlis171 .NET) (compiled Sep 13 2010,14:28:38) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −31→30
Tmin = 0.898, Tmax = 1	k = −11→11
26193 measured reflections	l = −23→23

Refinement

Refinement on F	356 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.015	w1 = 1/[s^2(Fo)]
wR(F^2) = 0.01	(Δ/σ)max = 0.05
S = 1.45	Δρmax = 0.11 e Å^−3
4044 reflections	Δρmin = −0.12 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq
O(1)	0.244150 (12)	0.89978 (3)	0.381879 (16)	0.009
O(2)	0.312812 (12)	1.32898 (3)	0.420132 (16)	0.009
O(3)	0.180065 (12)	1.48920 (3)	0.333568 (16)	0.009
O(4)	0.110209 (13)	1.05177 (3)	0.289919 (18)	0.014
N(1)	0.071508 (14)	1.48316 (4)	0.104899 (18)	0.008
C(1)	0.232422 (16)	1.31823 (4)	0.368854 (19)	0.007
C(2)	0.188278 (16)	1.07222 (4)	0.34252 (2)	0.008
C(3)	0.042131 (17)	1.27361 (4)	0.02931 (2)	0.01
C(4)	−0.003279 (16)	1.64920 (4)	0.09561 (2)	0.009
H(7)	0.214453	0.731108	0.365096	0.0258 (14)*
H(1)	−0.006876	1.185035	0.061652	0.0271 (12)*
H(2)	0.022716	1.800839	0.1504	0.0253 (12)*
H(3)	−0.053474	1.555879	0.123723	0.0238 (12)*
H(4)	0.120809	1.578237	0.083114	0.0223 (14)*
H(5)	0.099183	1.158661	0.040106	0.0288 (13)*
H(6)	0.097449	1.428288	0.190862	0.0257 (15)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00756 (7)	0.00614 (6)	0.01286 (8)	−0.00006 (5)	0.00126 (6)	0.00038 (5)
O(2)	0.00636 (7)	0.00734 (7)	0.01207 (7)	−0.00058 (5)	0.00083 (6)	−0.00069 (5)
O(3)	0.00881 (7)	0.00665 (6)	0.00995 (7)	0.00126 (5)	0.00120 (6)	0.00079 (5)
O(4)	0.00751 (8)	0.00975 (7)	0.01988 (9)	−0.00092 (6)	−0.00241 (7)	−0.00165 (6)
N(1)	0.00614 (8)	0.00935 (8)	0.00790 (7)	−0.00020 (6)	−0.00015 (6)	0.00026 (6)
C(1)	0.00637 (9)	0.00579 (7)	0.00736 (8)	0.00007 (6)	0.00109 (7)	0.00000 (6)
C(2)	0.00645 (9)	0.00638 (8)	0.00891 (8)	−0.00044 (6)	0.00077 (7)	−0.00053 (6)
C(3)	0.00880 (10)	0.00756 (8)	0.01147 (9)	0.00126 (7)	0.00038 (8)	0.00028 (7)
C(4)	0.00823 (9)	0.00997 (9)	0.00923 (9)	0.00006 (7)	0.00179 (7)	−0.00190 (7)

Geometric parameters (Å, º)

O1—C2	1.3104 (3)	C2—O4	1.2147 (3)
O2—C1	1.2393 (3)	N1—C4	1.4911 (3)
O3—C1	1.2654 (2)	N1—C3	1.4887 (3)
C1—C2	1.5526 (3)	C3—C4^i	1.5160 (3)
O2—C1—O3	127.01 (3)	O1—C2—C1	112.65 (3)
O2—C1—C2	118.61 (3)	C4—N1—C3	111.36 (3)
O3—C1—C2	114.39 (2)	N1—C3—C4^i	109.90 (3)
O4—C2—O1	126.11 (3)	N1—C4—C3^i	109.59 (3)
O4—C2—C1	121.24 (2)

Symmetry code: (i) −x, −y+3, −z.

(IIC)

Crystal data

C4H7NO4	F(000) = 560
Mr = 133.11	Dx = 1.704 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.82035 (12) Å	Cell parameters from 20347 reflections
b = 5.68088 (3) Å	θ = 3.5–45.3°
c = 12.09343 (8) Å	µ = 0.15 mm^−1
β = 107.3321 (8)°	T = 100 K
V = 1037.53 (1) Å^3	0.32 × 0.13 × 0.11 mm
Z = 8

Data collection

Xcalibur, Eos, Gemini ultra diffractometer	4172 independent reflections
Graphite monochromator	3729 reflections with I > 2σ(I)
Detector resolution: 16.2413 pixels mm^-1	Rint = 0.016
ω scans	θmax = 45.4°, θmin = 3.5°
Absorption correction: gaussian CrysAlis PRO, Oxford Diffraction Ltd., Version 1.171.34.41 (release 13-09-2010 CrysAlis171 .NET) (compiled Sep 13 2010,14:28:38) Numerical absorption correction based on gaussian integration over a multifaceted crystal model	h = −26→31
Tmin = 0.967, Tmax = 1.034	k = −11→11
15647 measured reflections	l = −24→24

Refinement

Refinement on F	89 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.021	w1 = 1/[s^2(Fo)]
wR(F^2) = 0.013	(Δ/σ)max = 0.001
S = 2.03	Δρmax = 0.24 e Å^−3
4302 reflections	Δρmin = −0.21 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq
O(1)	0.244129 (10)	0.89974 (2)	0.381860 (13)	0.009
O(2)	0.312828 (10)	1.32903 (2)	0.420149 (13)	0.009
O(3)	0.180055 (10)	1.48923 (2)	0.333537 (12)	0.009
O(4)	0.110226 (10)	1.05181 (3)	0.289882 (15)	0.014
N(1)	0.071514 (11)	1.48316 (3)	0.104907 (14)	0.008
C(1)	0.232417 (13)	1.31823 (3)	0.368837 (16)	0.007
C(2)	0.188277 (13)	1.07225 (3)	0.342521 (16)	0.008
C(3)	0.042171 (14)	1.27368 (3)	0.029316 (17)	0.01
C(4)	−0.003287 (13)	1.64922 (3)	0.095632 (17)	0.009
H(7)	0.21444	0.73103	0.365088	0.0276 (12)*
H(1)	−0.006849	1.185085	0.061634	0.0281 (10)*
H(2)	0.022723	1.800876	0.150414	0.0264 (10)*
H(3)	−0.053483	1.555862	0.123728	0.0264 (9)*
H(4)	0.120813	1.578244	0.083112	0.0266 (12)*
H(5)	0.0992	1.158625	0.040109	0.0301 (10)*
H(6)	0.09745	1.428286	0.190865	0.0268 (12)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.00737 (6)	0.00621 (5)	0.01285 (6)	−0.00004 (4)	0.00095 (5)	0.00038 (4)
O(2)	0.00611 (6)	0.00743 (5)	0.01214 (6)	−0.00066 (4)	0.00049 (5)	−0.00073 (4)
O(3)	0.00857 (6)	0.00671 (5)	0.01009 (6)	0.00135 (4)	0.00096 (5)	0.00083 (4)
O(4)	0.00727 (7)	0.00982 (6)	0.02005 (7)	−0.00095 (5)	−0.00287 (6)	−0.00165 (5)
N(1)	0.00589 (7)	0.00946 (6)	0.00786 (6)	−0.00014 (5)	−0.00064 (5)	0.00027 (5)
C(1)	0.00614 (7)	0.00585 (6)	0.00735 (6)	0.00014 (5)	0.00082 (6)	0.00004 (5)
C(2)	0.00617 (8)	0.00639 (6)	0.00903 (7)	−0.00045 (5)	0.00046 (6)	−0.00045 (5)
C(3)	0.00865 (8)	0.00761 (6)	0.01146 (7)	0.00130 (6)	0.00001 (6)	0.00032 (5)
C(4)	0.00798 (8)	0.01005 (7)	0.00923 (7)	0.00004 (6)	0.00138 (6)	−0.00197 (5)

Geometric parameters (Å, º)

O1—C2	1.3104 (3)	C2—O4	1.2147 (3)
O2—C1	1.2393 (3)	N1—C4	1.4911 (3)
O3—C1	1.2654 (2)	N1—C3	1.4881 (3)
C1—C2	1.5526 (3)
O2—C1—O3	127.01 (3)	O4—C2—C1	121.24 (2)
O2—C1—C2	118.61 (3)	O1—C2—C1	112.65 (3)
O3—C1—C2	114.39 (2)	C4—N1—C3	111.36 (3)
O4—C2—O1	126.11 (3)