Crystal structure of ammonium bis­(pyridine-2,6-di­carboxyl­ato-κ3O,N,O′)chromate(III) from synchrotron data

Moon, D.; Choi, J.-H.

doi:10.1107/S2056989015001152

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ISSN: 2056-9890

Volume 71| Part 2| February 2015| Pages 210-212

doi:10.1107/S2056989015001152

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Crystal structure of ammonium bis(pyridine-2,6-dicarboxylato-κ³O,N,O′)chromate(III) from synchrotron data

Dohyun Moon ^a and Jong-Ha Choi ^b ^*

^aPohang Accelerator Laboratory, POSTECH, Pohang 790-784, Republic of Korea, and ^bDepartment of Chemistry, Andong National University, Andong 760-749, Republic of Korea
^*Correspondence e-mail: jhchoi@anu.ac.kr

Edited by J. Simpson, University of Otago, New Zealand (Received 6 January 2015; accepted 19 January 2015; online 24 January 2015)

The structure of the title compound, (NH₄)[Cr(pydc)₂] (pydc is pyridine-2,6-dicarboxylate, C₇H₃NO₄), has been determined from synchrotron data. The Cr^III ion and the N atom of the ammonium cation are located on a crystallographic fourfold rotoinversion axis (-4). The Cr^III cation is coordinated by four O atoms and the two N atoms of two meridional pydc ligands, displaying a distorted octahedral geometry. The Cr—N and Cr—O bond lengths are 1.9727 (15) and 1.9889 (9) Å, respectively. The crystal structure is stabilized by intermolecular hydrogen bonds involving the N–H groups of the ammonium cation and pyridine C–H groups as donors and the non-coordinating carbonyl O atoms as acceptors.

Keywords: Crystal structure; synchrotron radiation; pyridine-2,6-dicarboxylate; ammonium cation; chromate(III) complex; meridional configuration; hydrogen bonding.

CCDC reference: 1044324

1. Chemical context

Pyridine-2,6-dicarboxylic acid (also known as dipicolinic acid and abbreviated here as H₂pydc) can coordinate a metal center as a neutral molecule (H₂pydc), the univalent anion (Hpydc⁻), or the divalent anion (pydc²⁻). In particular, the pyridine-2,6-dicarboxylate ligand frequently acts as a meridional tridentate ligand and sometimes also as a bidentate or bridging ligand (Park et al., 2007 ). The first [Cr(pydc)₂]⁻ complex was prepared as the Na⁺ salt according to the literature (Hoggard & Schmidtke, 1973 ) and its crystal structure determined using synchrotron data. Structural analysis showed the compound to be a dihydrate (Dai et al., 2006 ; González-Baró et al., 2008 ) rather than the 1.5 or 2.5 hydrates that had been suggested previously (Hoggard & Schmidtke, 1973; Fürst et al., 1979 ). The crystal structures of K[Cr(pydc)₂] (Hakimi et al., 2012 ) and Rb[Cr(pydc)₂] (Fürst et al., 1979) have also been reported previously but the structure of the ammonium salt is not known.

Here we report the crystal structure of (NH₄)[Cr(pydc)₂] in order to clarify unambiguously the bonding mode of the two pyridine-2,6-dicarboxylato ligands and the structural arrangement of this ammonium salt.

2. Structural commentary

Counter-ionic species play a very important role in coordination chemistry. The structure reported here is another example of a [Cr(pydc)₂]⁻ salt but with a different cation. The structural analysis shows that the two tridentate pyridine-2,6-dicarboxylate (pydc) dianions octahedrally coordinate to the Cr^III metal center through one N atom and two carboxylate O atoms in a meridional arrangement. The Cr^III ion is located on a crystallographic fourfold rotoinversion axis ( $[\overline{4}]$ ). An ellipsoid plot of title complex together with the atomic numbering is illustrated in Fig. 1.

Figure 1
The molecular structure of (NH₄)[Cr(pydc)₂], showing the atom-numbering scheme. Non-H atoms are shown as displacement ellipsoids drawn at the 50% probability level.

The Cr—N and Cr—O bond lengths to the pydc²⁻ ligands are 1.9727 (15) and 1.9889 (9) Å, respectively, and these lengths agree well with the values observed in the literature for complexes with the same [Cr(pydc)₂]⁻ anion (Fürst et al., 1979; Dai et al., 2006; González-Baró et al., 2008; Zhou et al., 2009 ; Hakimi et al., 2012). The coordinating pyridine N atoms are in a mutually trans arrangement. Both tridendate pydc²⁻ ligands are nearly planar and are oriented perpendicular to one another. Bond angles about the central chromium atom are 79.10 (3) for N1—Cr1—O1, 100.90 (3) for N1—Cr1—O1ⁱ and 158.20 (5)° for O1ⁱ—Cr1—O1ⁱⁱ, indicating a distorted octahedral coordination environment [symmetry codes: (i) −y + $[{5\over 4}]$ , x − $[{3\over 4}]$ , −z + $[{5\over 4}]$ ; (ii) y + $[{3\over 4}]$ , −x + $[{5\over 4}]$ , −z + $[{5\over 4}]$ ]. The C1—O1 and C1—O2 bond lengths within the carboxylate group of the pydc²⁻ ligand are 1.2941 (15) and 1.2223 (14) Å, respectively, and can be compared with values of 1.298 (5) and 1.224 (5) Å for Rb[Cr(pydc)₂] (Fürst et al., 1979). The ammonium cation, also lying on a crystallographic fourfold rotoinversion axis ( $[\overline{4}]$ ), shows a distorted tetrahedral geometry of the hydrogen atoms around the central nitrogen atom with N—H distances of 0.846 (9) Å and the H—N—H angles ranging from 105.36 (9) to 118.06 (9)°.

3. Supramolecular features

The pattern of hydrogen bonding around the cation is very similar to the coordination environment in the related potassium salt (Hakimi et al., 2012). The non-coordinating carbonyl O atom forms weak C—H⋯O hydrogen bonds that contribute to the crystal packing. The ammonium cation is also linked to the carbonyl O atoms from four neighboring pydc²⁻ ligands through classical N—H⋯O hydrogen bonds (Table 1). An extensive array of these contacts generate a three-dimensional network of molecules stacked along the a-axis direction (Fig. 2). π–π interactions involving adjacent pyridine rings further link the components of the structure into a three-dimensional network. The centroid–centroid distance between the π–π stacked rings (N1/C2–C4/C3^iv/C2^iv)⋯(N1^v/C2^v–C4^v/C3^vi/C2^vi) is 3.572 (2) Å [symmetry codes: (iv) 2 − x, $[{1\over 2}]$ − y, z; (v) $[{1\over 2}]$ + x, y, $[{3\over 2}]$ − z; (vi) $[{5\over 2}]$ − x, $[{1\over 2}]$ − y, $[{3\over 2}]$ − z].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯O2ⁱ	0.93	2.50	3.4071 (15)	167
N1S—H1S⋯O2ⁱⁱ	0.85 (1)	2.04 (1)	2.8462 (11)	158 (2)
Symmetry codes: (i) $[-x+{\script{3\over 2}}, -y+{\script{3\over 2}}, -z+{\script{3\over 2}}]$ ; (ii) $[-y+{\script{5\over 4}}, x+{\script{1\over 4}}, -z+{\script{5\over 4}}]$ .

Figure 2
Crystal packing of (NH₄)[Cr(pydc)₂], viewed perpendicular to the bc plane. Dashed lines represent C—H⋯O (purple) and N—H⋯O (blue) hydrogen-bonding interactions.

4. Database survey

A search of the Cambridge Structural Database (Version 5.35, May 2014 with one update; Groom & Allen, 2014 ) indicates a total of 16 hits for Cr^III complexes with a complex anion [Cr(pydc)₂]⁻ unit. Many crystal structures of [Cr(pydc)₂]⁻ with inorganic, organic or complex counter-cations such as K⁺ (Hakimi et al., 2012), Na⁺ (Dai et al., 2006; González-Baró et al., 2008; Zhou et al., 2009), Rb⁺ (Fürst et al., 1979), creatH⁺ (creat = creatinine; Aghabozorg et al., 2008 ), 4,4′-bpyH⁺ (bpy = bipyridine; Soleimannejad et al., 2008 ), dmpH⁺ (dmp = 2,9-dimethyl-1,10-phenanthrone; Aghajani et al., 2009 ), 2-apymH⁺ (2-apym = 2-aminopyrimidine; Eshtiagh-Hosseini et al., 2010 ), [Cr(tpy)(pydc)]⁺ [tpy = 2,6-bis(2-pyridyl)pyridine; Casellato et al., 1991 ] and [Ag(atr)₂]⁺ (atr = 3-amino-1H-1,2,4-triazole; Tabatabaee et al., 2011 ) have been determined.

Alternative coordination behaviors of the pydc ligands are found in [Cu(Hpydc)₂]·3H₂O, which has one neutral H₂pydc and one divalent pydc²⁻ ligand, while [Ni(Hpydc)₂]·3H₂O (Nathan & Mai, 2000 ) has two meridional univalent Hpydc⁻ ligands. The ligands in [Ni(cyclam)(Hpydc)₂]·2H₂O (Park et al., 2007) and Na₂[Pt(Hpydc)₂]·6H₂O are monodentate and bidentate, respectively, while Hpydc⁻ is tridentate in the complexes [Cu(Hpydc)₂]·3H₂O and [Ni(Hpydc)₂]·3H₂O (Nathan & Mai, 2000).

5. Synthesis and crystallization

All chemicals were reagent-grade materials and were used without further purification. The starting material, Na[Cr(pydc)₂]·2H₂O was prepared as described previously (Hoggard & Schmidtke, 1973). The sodium salt (0.20 g) was dissolved in 15 mL of water at 323 K and added to 3 mL of water containing 0.5 g of NH₄Cl. The resulting solution was filtered and allowed to stand at room temperature for several days to give brown block-like crystals of the ammonium salt NH₄[Cr(pydc)₂] suitable for X-ray structural analysis.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances of 0.95 (ring H atoms) and with U_iso(H) = 1.2 U_eq(parent atom). The H atoms of the ammonium cation were located from difference Fourier maps and refined with restraints and a fixed N—H distance of 0.87 Å, with U_iso(H) = 1.2U_eq(N). One reflection with F_o<<<F_c was omitted from the final refinement cycles. The slightly low fraction of measured reflections results from the geometry of the 2D-SMC beamline goniostat.

Table 2
Experimental details

Crystal data
Chemical formula	(NH₄)[Cr(C₇H₃NO₄)₂]
M_r	400.25
Crystal system, space group	Tetragonal, I4₁/a
Temperature (K)	301
a, c (Å)	7.0305 (10), 28.995 (6)
V (Å³)	1433.2 (5)
Z	4
Radiation type	Synchrotron, λ = 0.62998 Å
μ (mm⁻¹)	0.62
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	ADSC Q210 CCD area detector
Absorption correction	Empirical (using intensity measurements) (HKL3000sm SCALEPACK; Otwinowski & Minor, 1997 )
T_min, T_max	0.925, 0.940
No. of measured, independent and observed [I > 2σ(I)] reflections	6841, 943, 903
R_int	0.052
(sin θ/λ)_max (Å⁻¹)	0.695

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.081, 1.21
No. of reflections	943
No. of parameters	63
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.31, −0.86
Computer programs: PAL ADSC Quantum-210 ADX (Arvai & Nielsen, 1983 ), HKL3000sm (Otwinowski & Minor, 1997), SHELXT2014/5 (Sheldrick, 2015a ), SHELXL2014/7 (Sheldrick, 2008 , 2015b ), DIAMOND (Brandenburg, 2007 ) and publCIF (Westrip 2010 ).

Supporting information

CCDC reference: 1044324

Crystal structure: contains datablock I. DOI: 10.1107/S2056989015001152/sj5438sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015001152/sj5438Isup2.hkl

checkCIF report

Chemical context top

Pyridine-2,6-dicarboxylic acid (also known as dipicolinic acid and abbreviated here as H₂pydc) can coordinate a metal center as a neutral molecule (H₂pydc), the univalent anion (Hpydc^-), or the divalent anion (pydc^2-). In particular, the pyridine-2,6-dicarboxylate ligand frequently acts as a meridional tridentate ligand and sometimes also as a bidentate or bridging ligand (Park et al., 2007). The first [Cr(pydc)₂]^- complex was prepared as the Na⁺ salt according to the literature (Hoggard & Schmidtke, 1973) and its crystal structure determined using synchrotron data. Structural analysis showed the compound to be a dihydrate (Dai et al., 2006; González-Baró et al., 2008) rather than the 1.5 or 2.5 hydrates that had been suggested previously (Hoggard & Schmidtke, 1973; Fürst et al., 1979). The crystal structures of K[Cr(pydc)₂] (Hakimi et al., 2012) and Rb[Cr(pydc)₂] (Fürst et al., 1979) have also been reported previously but the structure of the ammonium salt is not known. Here we report the crystal structure of NH₄[Cr(pydc)₂] in order to clarify unambiguously the bonding mode of the two pyridine-2,6-dicarboxylato ligands and the geometrical arrangement of this ammonium salt.

Structural commentary top

Counter-ionic species play a very important role in coordination chemistry. The structure reported here is another example of a [Cr(pydc)₂]^- salt but with a different cation. The structural analysis shows that the two tridentate pyridine-2,6-dicarboxylate (pydc) dianions octahedrally coordinate to the Cr^III metal center through one N atom and two carboxylate O atoms in a meridional arrangement. The Cr^III ion is located on a crystallographic fourfold rotoinversion axis (4). An ellipsoid plot of title complex together with the atomic numbering is illustrated in Fig. 1.

The Cr—N and Cr—O bond lengths to the pydc ligands are 1.9727 (15) and 1.9889 (9) Å, respectively, and these lengths agree well with the values observed in the literature for complexes with the same [Cr(pydc)₂]^- anion (Fürst et al., 1979; Dai et al., 2006; González-Baró et al., 2008; Zhou et al., 2009; Hakimi et al., 2012). The coordinating pyridine N atoms are in a mutually trans arrangement. Both tridendate pydc^2- ligands are nearly planar and are oriented perpendicular to one another. Bond angles about the central chromium atom are 79.10 (3) for N1—Cr1—O1, 100.90 (3) for N1—Cr1—O1ⁱ and 158.20 (5)° for O1^i-–Cr1—O1ⁱⁱ, indicating a distorted octahedral coordination environment [symmetry codes: (i) -y+5/4, x-3/4, -z+5/4; (ii) y+3/4, -x+5/4, -z+5/4]. The C1—O1 and C1—O2 bond lengths within the carboxylate group of the pydc^2- ligand are 1.2941 (15) and 1.2223 (14) Å, respectively, and can be compared with values of 1.298 (5) and 1.224 (5) Å for Rb[Cr(pydc)₂] (Fürst et al., 1979). The ammonium cation, also lying on a crystallographic fourfold rotoinversion axis (4), shows a distorted tetrahedral geometry of the hydrogen atoms around the central nitrogen atom with N—H distances of 0.846 (9) Å and the H—N—H angles ranging from 105.36 (9) to 118.06 (9)°.

Supramolecular features top

The pattern of hydrogen bonding around the cation is very similar to the coordination environment in the related potassium salt (Hakimi et al., 2012). The non-coordinating carbonyl O atom forms weak C—H···O hydrogen bonds that contribute to the crystal packing. The ammonium cation is also linked to the carbonyl O atoms from four neighboring pydc^2- ligands through classical N—H···O hydrogen bonds (Table 1). An extensive array of these contacts generate a three-dimensional network of molecules stacked along the a-axis direction (Fig. 2). π–π interactions involving adjacent pyridine rings further link the components of the structure into a three-dimensional network. The centroid–centroid distances between the π–π stacked rings (N1/C2–C4/C3^iv/C2^iv)···(N1^v/C2^v–C4^v/C3^vi/C2^vi) is 3.572 (2) Å [symmetry codes: (iv) 2 - x, 1/2 - y, z; (v) 1/2 + x, y, 3/2 - z; (vi) 5/2 -x, 1/2 - y, 3/2 - z].

Database survey top

A search of the Cambridge Structural Database (Version 5.35, May 2014 with one update; Groom & Allen, 2014) indicates a total of 16 hits for Cr^III complexes with a complex anion [Cr(pydc)₂]^- unit. Many crystal structures of [Cr(pydc)₂]^- with inorganic, organic or complex counter-cations such as K⁺ (Hakimi et al., 2012), Na⁺ (Dai et al., 2006; González-Baró et al., 2008; Zhou et al., 2009), Rb⁺ (Fürst et al., 1979), creatH⁺ (creat = creatinine; Aghabozorg et al., 2008), 4,4'-bpyH⁺ (bpy = bipyridine; Soleimannejad et al., 2008), dmpH⁺ (dmp = 2,9-dimethyl-1,10-phenanthrone; Aghajani et al., 2009), 2-apymH⁺ (2-apym = 2-aminopyrimidine; Eshtiagh-Hosseini et al., 2010), [Cr(tpy)(pydc)]⁺ [tpy = 2,6-bis(2-pyridyl)pyridine; Casellato et al., 1991] and [Ag(atr)₂]⁺ (atr = 3-amino-1H-1,2,4-triazole; Tabatabaee et al., 2011) have been determined.

Alternative coordination behaviors of the pydc ligands are found in [Cu(Hpydc)₂]·3H₂O, which has one neutral H₂pydc and one divalent pydc^2- ligand, while [Ni(Hpydc)₂]·3H₂O (Nathan & Mai, 2000) has two meridional univalent Hpydc^- ligands. The ligands in [Ni(cyclam)(Hpydc)₂]·2H₂O (Park et al., 2007) and Na₂[Pt(Hpydc)₂]·6H₂O are monodentate and bidentate, respectively, while Hpydc^- is tridentate in the complexes [Cu(Hpydc)₂]·3H₂O and [Ni(Hpydc)₂]·3H₂O (Nathan & Mai, 2000).

Synthesis and crystallization top

All chemicals were reagent-grade materials and were used without further purification. The starting material, Na[Cr(pydc)₂]·2H₂O was prepared as described previously (Hoggard & Schmidtke, 1973). The sodium salt (0.20 g) was dissolved in 15 ml of water at 323 K and added to 3 ml of water containing 0.5 g of NH₄Cl. The resulting solution was filtered and allowed to stand at room temperature for several days to give brown block-like crystals of the ammonium salt NH₄[Cr(pydc)₂] suitable for X-ray structural analysis.

Refinement top

Related literature top

For related literature, see: Aghabozorg et al. (2008); Aghajani et al. (2009); Casellato et al. (1991); Dai et al. (2006); Eshtiagh-Hosseini, Yousefi, Mirzaei, Chen, Beyramabadi, Shokrollahi & Aghaei (2010); Fürst et al. (1979); González-Baró, Pis-Diez, Pis-Diez & Parajón-Costa (2008); Groom & Allen (2014); Hakimi et al. (2012); Hoggard & Schmidtke (1973); Nathan & Mai (2000); Park et al. (2007); Soleimannejad et al. (2008); Tabatabaee et al. (2011); Zhou et al. (2009).

Computing details top

Data collection: PAL ADSC Quantum-210 ADX (Arvai & Nielsen, 1983); cell refinement: HKL3000sm (Otwinowski & Minor, 1997); data reduction: HKL3000sm (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2008, 2015b); molecular graphics: DIAMOND (Brandenburg, 2007); software used to prepare material for publication: publCIF (Westrip 2010).

Figures top

	Fig. 1. The molecular structure of NH₄[Cr(pydc)₂], showing the atom-numbering scheme. Non-H atoms are shown as displacement ellipsoids drawn at the 50% probability level.
	Fig. 2. Crystal packing of NH₄[Cr(pydc)₂], viewed perpendicular to the bc plane. Dashed lines represent C—H···O (purple) and N—H···O (blue) hydrogen-bonding interactions.

Bis(pyridine-2,6-dicarboxylato-κ³O,N,O')chromate(III) top

Crystal data top

(NH₄)[Cr(C₇H₃NO₄)₂]	D_x = 1.855 Mg m⁻³
M_r = 400.25	Synchrotron radiation, λ = 0.62998 Å
Tetragonal, I4₁/a	Cell parameters from 20017 reflections
a = 7.0305 (10) Å	θ = 0.4–33.6°
c = 28.995 (6) Å	µ = 0.62 mm⁻¹
V = 1433.2 (5) Å³	T = 301 K
Z = 4	Block, brown
F(000) = 812	0.15 × 0.10 × 0.10 mm

Data collection top

ADSC Q210 CCD area detector diffractometer	903 reflections with I > 2σ(I)
Radiation source: PLSII 2D bending magnet	R_int = 0.052
ω scan	θ_max = 26.0°, θ_min = 4.0°
Absorption correction: empirical (using intensity measurements) (HKL3000sm SCALEPACK; Otwinowski & Minor, 1997)	h = −9→9
T_min = 0.925, T_max = 0.940	k = −9→9
6841 measured reflections	l = −36→36
943 independent reflections

Refinement top

Refinement on F²	1 restraint
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.028	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.081	w = 1/[σ²(F_o²) + (0.0461P)² + 0.7347P] where P = (F_o² + 2F_c²)/3
S = 1.21	(Δ/σ)_max = 0.001
943 reflections	Δρ_max = 0.31 e Å⁻³
63 parameters	Δρ_min = −0.86 e Å⁻³

Crystal data top

(NH₄)[Cr(C₇H₃NO₄)₂]	Z = 4
M_r = 400.25	Synchrotron radiation, λ = 0.62998 Å
Tetragonal, I4₁/a	µ = 0.62 mm⁻¹
a = 7.0305 (10) Å	T = 301 K
c = 28.995 (6) Å	0.15 × 0.10 × 0.10 mm
V = 1433.2 (5) Å³

Data collection top

ADSC Q210 CCD area detector diffractometer	943 independent reflections
Absorption correction: empirical (using intensity measurements) (HKL3000sm SCALEPACK; Otwinowski & Minor, 1997)	903 reflections with I > 2σ(I)
T_min = 0.925, T_max = 0.940	R_int = 0.052
6841 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.028	1 restraint
wR(F²) = 0.081	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	Δρ_max = 0.31 e Å⁻³
943 reflections	Δρ_min = −0.86 e Å⁻³
63 parameters

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cr1	1.0000	0.2500	0.6250	0.01282 (14)
O1	0.88412 (13)	0.50247 (12)	0.63797 (3)	0.0205 (2)
O2	0.78279 (14)	0.69538 (13)	0.69398 (4)	0.0261 (2)
N1	1.0000	0.2500	0.69303 (5)	0.0133 (3)
C1	0.86229 (15)	0.55077 (15)	0.68071 (4)	0.0163 (2)
C2	0.93527 (14)	0.40403 (15)	0.71495 (4)	0.0142 (2)
C3	0.93425 (15)	0.41005 (17)	0.76260 (4)	0.0189 (2)
H3	0.8912	0.5171	0.7783	0.023*
C4	1.0000	0.2500	0.78645 (6)	0.0201 (3)
H4	1.0000	0.2500	0.8185	0.024*
N1S	0.5000	0.7500	0.6250	0.0223 (4)
H1S	0.502 (3)	0.8529 (19)	0.6099 (7)	0.027*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cr1	0.01591 (16)	0.01591 (16)	0.0066 (2)	0.000	0.000	0.000
O1	0.0286 (4)	0.0193 (4)	0.0134 (5)	0.0055 (3)	−0.0013 (3)	0.0013 (3)
O2	0.0304 (5)	0.0222 (4)	0.0258 (5)	0.0098 (3)	−0.0009 (3)	−0.0037 (3)
N1	0.0146 (5)	0.0171 (6)	0.0082 (7)	0.0008 (4)	0.000	0.000
C1	0.0159 (4)	0.0170 (5)	0.0160 (6)	0.0004 (3)	−0.0013 (4)	−0.0005 (4)
C2	0.0133 (4)	0.0175 (4)	0.0117 (5)	0.0001 (3)	−0.0005 (3)	−0.0016 (3)
C3	0.0171 (5)	0.0258 (5)	0.0137 (6)	−0.0006 (4)	0.0005 (3)	−0.0059 (4)
C4	0.0199 (7)	0.0324 (8)	0.0078 (8)	−0.0021 (5)	0.000	0.000
N1S	0.0220 (6)	0.0220 (6)	0.0229 (12)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Cr1—N1	1.9727 (15)	N1—C2	1.3355 (12)
Cr1—N1ⁱ	1.9727 (15)	C1—C2	1.5208 (15)
Cr1—O1	1.9889 (9)	C2—C3	1.3824 (16)
Cr1—O1ⁱⁱ	1.9889 (9)	C3—C4	1.3993 (15)
Cr1—O1ⁱ	1.9889 (9)	C3—H3	0.9300
Cr1—O1ⁱⁱⁱ	1.9889 (9)	C4—C3ⁱⁱⁱ	1.3992 (15)
O1—C1	1.2941 (15)	C4—H4	0.9300
O2—C1	1.2223 (14)	N1S—H1S	0.846 (9)
N1—C2ⁱⁱⁱ	1.3354 (12)

N1—Cr1—N1ⁱ	180.0	C2ⁱⁱⁱ—N1—C2	123.19 (15)
N1—Cr1—O1	79.10 (3)	C2ⁱⁱⁱ—N1—Cr1	118.40 (7)
N1ⁱ—Cr1—O1	100.90 (3)	C2—N1—Cr1	118.41 (7)
N1—Cr1—O1ⁱⁱ	100.90 (3)	O2—C1—O1	125.02 (11)
N1ⁱ—Cr1—O1ⁱⁱ	79.10 (3)	O2—C1—C2	120.87 (11)
O1—Cr1—O1ⁱⁱ	92.049 (10)	O1—C1—C2	114.02 (9)
N1—Cr1—O1ⁱ	100.90 (3)	N1—C2—C3	120.14 (11)
N1ⁱ—Cr1—O1ⁱ	79.10 (3)	N1—C2—C1	110.77 (10)
O1—Cr1—O1ⁱ	92.049 (10)	C3—C2—C1	129.04 (10)
O1ⁱⁱ—Cr1—O1ⁱ	158.20 (5)	C2—C3—C4	117.88 (11)
N1—Cr1—O1ⁱⁱⁱ	79.10 (3)	C2—C3—H3	121.1
N1ⁱ—Cr1—O1ⁱⁱⁱ	100.90 (3)	C4—C3—H3	121.1
O1—Cr1—O1ⁱⁱⁱ	158.20 (5)	C3ⁱⁱⁱ—C4—C3	120.77 (16)
O1ⁱⁱ—Cr1—O1ⁱⁱⁱ	92.049 (10)	C3ⁱⁱⁱ—C4—H4	119.6
O1ⁱ—Cr1—O1ⁱⁱⁱ	92.049 (10)	C3—C4—H4	119.6
C1—O1—Cr1	117.64 (7)

Cr1—O1—C1—O2	−175.18 (9)	O1—C1—C2—N1	−2.76 (12)
Cr1—O1—C1—C2	1.39 (12)	O2—C1—C2—C3	−3.27 (17)
C2ⁱⁱⁱ—N1—C2—C3	0.47 (7)	O1—C1—C2—C3	−179.99 (10)
Cr1—N1—C2—C3	−179.53 (7)	N1—C2—C3—C4	−0.90 (14)
C2ⁱⁱⁱ—N1—C2—C1	−177.04 (9)	C1—C2—C3—C4	176.10 (9)
Cr1—N1—C2—C1	2.96 (9)	C2—C3—C4—C3ⁱⁱⁱ	0.44 (7)
O2—C1—C2—N1	173.96 (9)

Symmetry codes: (i) y+3/4, −x+5/4, −z+5/4; (ii) −y+5/4, x−3/4, −z+5/4; (iii) −x+2, −y+1/2, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O2^iv	0.93	2.50	3.4071 (15)	167
N1S—H1S···O2^v	0.85 (1)	2.04 (1)	2.8462 (11)	158 (2)

Symmetry codes: (iv) −x+3/2, −y+3/2, −z+3/2; (v) −y+5/4, x+1/4, −z+5/4.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O2ⁱ	0.93	2.50	3.4071 (15)	166.5
N1S—H1S···O2ⁱⁱ	0.846 (9)	2.044 (11)	2.8462 (11)	158.1 (19)

Symmetry codes: (i) −x+3/2, −y+3/2, −z+3/2; (ii) −y+5/4, x+1/4, −z+5/4.

Experimental details

Crystal data
Chemical formula	(NH₄)[Cr(C₇H₃NO₄)₂]
M_r	400.25
Crystal system, space group	Tetragonal, I4₁/a
Temperature (K)	301
a, c (Å)	7.0305 (10), 28.995 (6)
V (Å³)	1433.2 (5)
Z	4
Radiation type	Synchrotron, λ = 0.62998 Å
µ (mm⁻¹)	0.62
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	ADSC Q210 CCD area detector diffractometer
Absorption correction	Empirical (using intensity measurements) (HKL3000sm SCALEPACK; Otwinowski & Minor, 1997)
T_min, T_max	0.925, 0.940
No. of measured, independent and observed [I > 2σ(I)] reflections	6841, 943, 903
R_int	0.052
(sin θ/λ)_max (Å⁻¹)	0.695

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.081, 1.21
No. of reflections	943
No. of parameters	63
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.31, −0.86

Computer programs: PAL ADSC Quantum-210 ADX (Arvai & Nielsen, 1983), HKL3000sm (Otwinowski & Minor, 1997), SHELXT2014/5 (Sheldrick, 2015a), SHELXL2014/7 (Sheldrick, 2008, 2015b), DIAMOND (Brandenburg, 2007), publCIF (Westrip 2010).

Acknowledgements

The X-ray crystallography experiment at the PLS-II 2D-SMC beamline was supported in part by MISP and POSTECH.

References

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Volume 71| Part 2| February 2015| Pages 210-212

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