Potassium (1-methoxy­carbonyl-2-methyl­prop-2-en-2-yl­idene)azinate

Reuter, C.; Neudörfl, J.M.; Schmalz, H.-G.

doi:10.1107/S1600536810010159

metal-organic compounds

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ISSN: 2056-9890

Volume 66| Part 4| April 2010| Page m461

doi:10.1107/S1600536810010159

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Potassium (1-methoxycarbonyl-2-methylprop-2-en-2-ylidene)azinate

Cédric Reuter,^a Jörg M. Neudörfl ^a and Hans-Günther Schmalz ^a ^*

^aDepartment für Chemie der Universität zu Köln, Greinstrasse 4, 50939 Köln, Germany
^*Correspondence e-mail: schmalz@uni-koeln.de

(Received 18 February 2010; accepted 18 March 2010; online 27 March 2010)

In the title compound, K⁺·C₆H₈NO₄⁻, the K⁺ cations have a coordination number of seven and are surrounded by four bidentate azinate anions. The methylene groups of the anions are always directed towards the coordinated potassium cations. The N—C—C—C torsion angle is 101.2 (2)°. The orthogonal non-conjugated nature of the salt confirms the supposed geometry and reactivity of this compound.

Related literature

For a short overview of peptidomimetics, see: Grauer et al. (2009 ); Vagner et al. (2008 ); Wu et al. (2008 ). For the synthesis of peptidomimetics, amino-acid-based building blocks play a key role in the assembly of these structures, see: Kemp, Boyd & Muendel (1991 ); Kemp, Curran et al. (1991 ); Beal et al. (2000 ); Kühne et al. (2008 ). A known deprotonation/protonation sequence (Bouveault & Wahl, 1901 ) was used in the synthesis of the title compound. The protonation of the title compound occurs exclusively at the α-position and no protonation of the methylene group was observed (Baldwin et al., 1977 ).

Experimental

Crystal data

K⁺·C₆H₈NO₄⁻
M_r = 197.23
Monoclinic, C m 2/c
a = 23.9269 (13) Å
b = 5.2909 (2) Å
c = 14.2510 (7) Å
β = 113.361 (2)°
V = 1656.21 (14) Å³
Z = 8
Mo Kα radiation
μ = 0.62 mm⁻¹
T = 100 K
0.20 × 0.15 × 0.03 mm

Data collection

Nonius KappaCCD diffractometer
6264 measured reflections
1810 independent reflections
1416 reflections with I > 2σ(I)
R_int = 0.041

Refinement

R[F² > 2σ(F²)] = 0.028
wR(F²) = 0.061
S = 1.01
1810 reflections
111 parameters
H-atom parameters constrained
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Selected bond lengths (Å)

K1—O1ⁱ	2.7036 (10)
K1—O2ⁱⁱ	2.7539 (11)
K1—O3ⁱ	2.7988 (11)
K1—O1	2.7994 (11)
K1—O2	2.8896 (10)
K1—O3ⁱⁱⁱ	2.8970 (12)
K1—O1ⁱⁱⁱ	2.9080 (11)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]$ ; (ii) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) x, y-1, z.

Data collection: COLLECT (Hooft, 1998 ); cell refinement: DENZO (Otwinowski & Minor, 1997 ); data reduction: DENZO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SCHAKAL99 (Keller, 1999 ); software used to prepare material for publication: PLATON (Spek, 2009 ), publCIF (Westrip, 2010 ) and ORTEP (Davenport et al., 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810010159/jj2024sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810010159/jj2024Isup2.hkl

checkCIF report

Comment top

In the last decade, interest in peptidomimetics has lead to a fast growing research field within organic chemistry (Grauer et al., 2009). Artificial peptide-like compounds are used to explore the principles of protein-protein interactions and their modulation (Vagner et al., 2008; Wu et al., 2008). In the synthesis of different peptidomimetics, amino acid based building blocks play a key role in the assembly of these structures (Kemp, Curran et al., 1991; Kemp, Boyd & Muendel, 1991; Beal et al., 2000; Kühne et al. 2008). In the context of our work we used an already known deprotonation/protonation sequence (Bouveault et al., 1901) to synthesize our compound. The protonation of the title compound occurs exclusively at the α-position whereas no protonation of the methylene group was observed (Baldwin et al., 1977).

In the title compound, C₆H₈KNO₄, (I),(Fig. 1), the deconjugation within the molecule combined with the high basicity of the nitro enolate provides a convincing explanation for the high selectivity of this reaction (Fig. 2). The crystal structure supports the assumption made by Baldwin et al. about the geometry of this potassium salt. The potassium cations in the crystal stucture have a coordination number of seven and are surrounded by four azinate anions with K—O distances from 2.704 (1) to 2.908 (1) Å (Fig. 3). These can either bind via the carbonyl group or the nitrogen-bonded oxygen atoms whereas both motifs can be found as bridging units. The resulting polar layers of potassium cations surrounded by oxygen atoms are perfectly shielded by the methyl and methylene residues (Fig. 4). This results in loose interactions between the different layers and explains the facile mechanical fissility of the crystals.

Related literature top

For a short overview of peptidomimetics, see: Grauer et al. (2009); Vagner et al. (2008); Wu et al. (2008). For the synthesis of peptidomimetics, amino-acid-based building blocks play a key role in the assembly of these structures, see: Kemp, Boyd & Muendel (1991); Kemp, Curran et al. (1991); Beal et al. (2000); Kühne et al. (2008). A known deprotonation/protonation sequence (Bouveault & Wahl, 1901) was used in the synthesis of the title compound. The protonation of the title compound occurs exclusively at the α-position and no protonation of the methylene group was observed (Baldwin et al., 1977).

Experimental top

The title compound, C₆H₈KNO₄, was prepared in good yield from methyl 3-methyl-2-nitrobut-2-enoate by deprotonation with potassium hydride. In a dry, argon-flushed 50 ml flask, 30.1 mmol of potassium hydride where suspended in 15 ml of dry THF. The suspension was cooled to 0 °C and a solution of 30.1 mmol methyl-3-methyl-2-nitrobut-2-enoate in 5 ml of THF was added via syringe over 30 min. After stirring for 5 h at room temperature a small amount of n-octanol was added at 0 °C to destroy the excess of potassium hydride. The paste was filtrated, washed three times with THF and dried in vacuo to give 4.950 g (25.1 mmol, 83%) of an ochre powder. A portion of the salt was recrystallized from MeOH/THF to give colourless prisms.

Computing details top

Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SCHAKAL99 (Keller, 1999); software used to prepare material for publication: PLATON (Spek, 2009), publCIF (Westrip, 2010) and ORTEP (Davenport et al., 1999).

Figures top

	Fig. 1. A view of (I). Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Protonation of the title compound (I).
	Fig. 3. Coordination sphere of an isolated potassium Cation.
	Fig. 4. View of the unit cell along the b-axis.

Potassium (1-methoxycarbonyl-2-methylprop-2-en-2-ylidene)azinate top

Crystal data top

K⁺·C₆H₈NO₄⁻	F(000) = 816
M_r = 197.23	D_x = 1.582 Mg m⁻³
Monoclinic, Cm2/c	Melting point: 180.7(10) K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 23.9269 (13) Å	Cell parameters from 6264 reflections
b = 5.2909 (2) Å	θ = 1.9–27.0°
c = 14.2510 (7) Å	µ = 0.62 mm⁻¹
β = 113.361 (2)°	T = 100 K
V = 1656.21 (14) Å³	Platlet, colourless
Z = 8	0.20 × 0.15 × 0.03 mm

Data collection top

Nonius KappaCCD diffractometer	1416 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.041
Graphite monochromator	θ_max = 27.0°, θ_min = 1.9°
Phi/ω–Scans scans	h = −30→30
6264 measured reflections	k = −6→6
1810 independent reflections	l = −18→18

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.061	H-atom parameters constrained
S = 1.01	w = 1/[σ²(F_o²) + (0.0266P)²] where P = (F_o² + 2F_c²)/3
1810 reflections	(Δ/σ)_max = 0.001
111 parameters	Δρ_max = 0.31 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

K⁺·C₆H₈NO₄⁻	V = 1656.21 (14) Å³
M_r = 197.23	Z = 8
Monoclinic, Cm2/c	Mo Kα radiation
a = 23.9269 (13) Å	µ = 0.62 mm⁻¹
b = 5.2909 (2) Å	T = 100 K
c = 14.2510 (7) Å	0.20 × 0.15 × 0.03 mm
β = 113.361 (2)°

Data collection top

Nonius KappaCCD diffractometer	1416 reflections with I > 2σ(I)
6264 measured reflections	R_int = 0.041
1810 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.028	0 restraints
wR(F²) = 0.061	H-atom parameters constrained
S = 1.01	Δρ_max = 0.31 e Å⁻³
1810 reflections	Δρ_min = −0.27 e Å⁻³
111 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.

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 (Å²) top

	x	y	z	U_iso*/U_eq
K1	0.269013 (15)	−0.06555 (6)	0.11206 (2)	0.01586 (11)
O1	0.22159 (5)	0.42337 (19)	0.06333 (8)	0.0183 (3)
O2	0.20272 (5)	0.26997 (19)	0.19103 (8)	0.0172 (2)
O3	0.15057 (5)	0.81224 (18)	−0.04385 (8)	0.0194 (3)
O4	0.07200 (5)	0.87761 (19)	0.00265 (8)	0.0191 (3)
N1	0.19003 (6)	0.4306 (2)	0.11777 (9)	0.0144 (3)
C1	0.14436 (7)	0.5975 (3)	0.10141 (11)	0.0142 (3)
C2	0.12553 (7)	0.7664 (3)	0.01413 (12)	0.0155 (3)
C3	0.04879 (8)	1.0606 (3)	−0.07901 (12)	0.0213 (4)
H3A	0.0089	1.1211	−0.0844	0.032*
H3B	0.0446	0.9813	−0.1436	0.032*
H3C	0.0771	1.2034	−0.0644	0.032*
C4	0.11349 (7)	0.5958 (3)	0.17409 (12)	0.0164 (3)
C5	0.12805 (8)	0.7705 (3)	0.24651 (12)	0.0221 (4)
H5A	0.1578	0.8947	0.2516	0.027*
H5B	0.1087	0.7716	0.2933	0.027*
C6	0.06556 (8)	0.3977 (3)	0.15837 (14)	0.0248 (4)
H6A	0.0312	0.4272	0.0930	0.037*
H6B	0.0514	0.4067	0.2141	0.037*
H6C	0.0828	0.2300	0.1577	0.037*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
K1	0.01789 (19)	0.0171 (2)	0.01396 (19)	0.00072 (15)	0.00778 (15)	−0.00055 (14)
O1	0.0217 (6)	0.0208 (6)	0.0198 (6)	0.0039 (5)	0.0160 (5)	0.0020 (5)
O2	0.0228 (6)	0.0153 (6)	0.0153 (6)	0.0030 (5)	0.0095 (5)	0.0046 (5)
O3	0.0205 (6)	0.0232 (6)	0.0190 (6)	0.0044 (5)	0.0125 (5)	0.0050 (5)
O4	0.0167 (6)	0.0236 (6)	0.0204 (6)	0.0070 (5)	0.0108 (5)	0.0086 (5)
N1	0.0175 (7)	0.0143 (7)	0.0130 (7)	−0.0020 (6)	0.0076 (6)	−0.0014 (6)
C1	0.0142 (8)	0.0147 (8)	0.0156 (8)	0.0008 (6)	0.0080 (7)	0.0004 (6)
C2	0.0160 (9)	0.0148 (8)	0.0159 (8)	−0.0013 (7)	0.0065 (7)	−0.0038 (7)
C3	0.0198 (9)	0.0241 (9)	0.0201 (9)	0.0057 (8)	0.0082 (8)	0.0083 (7)
C4	0.0159 (8)	0.0185 (9)	0.0169 (9)	0.0066 (7)	0.0086 (7)	0.0053 (7)
C5	0.0261 (10)	0.0238 (9)	0.0207 (9)	0.0074 (7)	0.0138 (8)	0.0046 (7)
C6	0.0237 (10)	0.0247 (9)	0.0320 (10)	0.0009 (7)	0.0175 (9)	0.0046 (8)

Geometric parameters (Å, º) top

K1—O1ⁱ	2.7036 (10)	O4—C2	1.3591 (18)
K1—O2ⁱⁱ	2.7539 (11)	O4—C3	1.4447 (18)
K1—O3ⁱ	2.7988 (11)	N1—C1	1.3516 (19)
K1—O1	2.7994 (11)	N1—K1^iv	3.2874 (12)
K1—O2	2.8896 (10)	C1—C2	1.451 (2)
K1—O3ⁱⁱⁱ	2.8970 (12)	C1—C4	1.4917 (19)
K1—O1ⁱⁱⁱ	2.9080 (11)	C1—K1^iv	3.4260 (15)
K1—C5ⁱⁱ	3.0584 (16)	C2—K1^iv	3.2747 (16)
K1—N1	3.2542 (13)	C3—H3A	0.9800
K1—C2ⁱⁱⁱ	3.2747 (16)	C3—H3B	0.9800
K1—N1ⁱⁱⁱ	3.2874 (12)	C3—H3C	0.9800
K1—C4ⁱⁱ	3.3355 (16)	C4—C5	1.325 (2)
O1—N1	1.2799 (14)	C4—C6	1.503 (2)
O1—K1ⁱ	2.7036 (10)	C4—K1^v	3.3355 (16)
O1—K1^iv	2.9081 (11)	C5—K1^v	3.0583 (16)
O2—N1	1.2856 (15)	C5—H5A	0.9500
O2—K1^v	2.7539 (11)	C5—H5B	0.9500
O3—C2	1.2219 (16)	C6—H6A	0.9800
O3—K1ⁱ	2.7989 (11)	C6—H6B	0.9800
O3—K1^iv	2.8970 (12)	C6—H6C	0.9800

O1ⁱ—K1—O2ⁱⁱ	162.38 (3)	N1—K1—C4ⁱⁱ	93.33 (4)
O1ⁱ—K1—O3ⁱ	59.21 (3)	C2ⁱⁱⁱ—K1—C4ⁱⁱ	145.11 (4)
O2ⁱⁱ—K1—O3ⁱ	106.36 (3)	N1ⁱⁱⁱ—K1—C4ⁱⁱ	118.00 (3)
O1ⁱ—K1—O1	71.80 (3)	N1—O1—K1ⁱ	146.87 (9)
O2ⁱⁱ—K1—O1	117.16 (3)	N1—O1—K1	98.95 (7)
O3ⁱ—K1—O1	127.70 (3)	K1ⁱ—O1—K1	108.20 (3)
O1ⁱ—K1—O2	116.67 (3)	N1—O1—K1^iv	95.49 (7)
O2ⁱⁱ—K1—O2	75.42 (2)	K1ⁱ—O1—K1^iv	78.14 (3)
O3ⁱ—K1—O2	168.78 (3)	K1—O1—K1^iv	135.94 (4)
O1—K1—O2	45.40 (3)	N1—O2—K1^v	120.14 (8)
O1ⁱ—K1—O3ⁱⁱⁱ	76.57 (3)	N1—O2—K1	94.53 (7)
O2ⁱⁱ—K1—O3ⁱⁱⁱ	118.77 (3)	K1^v—O2—K1	129.79 (4)
O3ⁱ—K1—O3ⁱⁱⁱ	103.16 (3)	C2—O3—K1ⁱ	136.99 (9)
O1—K1—O3ⁱⁱⁱ	80.73 (3)	C2—O3—K1^iv	96.80 (9)
O2—K1—O3ⁱⁱⁱ	85.11 (3)	K1ⁱ—O3—K1^iv	76.84 (3)
O1ⁱ—K1—O1ⁱⁱⁱ	101.86 (3)	C2—O4—C3	115.46 (12)
O2ⁱⁱ—K1—O1ⁱⁱⁱ	82.21 (3)	O1—N1—O2	117.81 (11)
O3ⁱ—K1—O1ⁱⁱⁱ	74.94 (3)	O1—N1—C1	123.09 (12)
O1—K1—O1ⁱⁱⁱ	135.94 (4)	O2—N1—C1	119.10 (12)
O2—K1—O1ⁱⁱⁱ	116.22 (3)	O1—N1—K1	58.18 (6)
O3ⁱⁱⁱ—K1—O1ⁱⁱⁱ	55.87 (3)	O2—N1—K1	62.27 (7)
O1ⁱ—K1—C5ⁱⁱ	96.14 (4)	C1—N1—K1	163.88 (10)
O2ⁱⁱ—K1—C5ⁱⁱ	72.78 (4)	O1—N1—K1^iv	61.71 (6)
O3ⁱ—K1—C5ⁱⁱ	90.87 (4)	O2—N1—K1^iv	127.10 (9)
O1—K1—C5ⁱⁱ	76.55 (4)	C1—N1—K1^iv	84.21 (8)
O2—K1—C5ⁱⁱ	79.00 (4)	K1—N1—K1^iv	107.96 (4)
O3ⁱⁱⁱ—K1—C5ⁱⁱ	157.29 (4)	N1—C1—C2	120.36 (13)
O1ⁱⁱⁱ—K1—C5ⁱⁱ	146.51 (4)	N1—C1—C4	117.74 (13)
O1ⁱ—K1—N1	93.48 (3)	C2—C1—C4	121.88 (13)
O2ⁱⁱ—K1—N1	98.04 (3)	N1—C1—K1^iv	72.68 (8)
O3ⁱ—K1—N1	150.55 (3)	C2—C1—K1^iv	71.72 (8)
O1—K1—N1	22.86 (3)	C4—C1—K1^iv	129.38 (10)
O2—K1—N1	23.19 (3)	O3—C2—O4	121.61 (14)
O3ⁱⁱⁱ—K1—N1	78.35 (3)	O3—C2—C1	129.29 (14)
O1ⁱⁱⁱ—K1—N1	125.49 (3)	O4—C2—C1	109.10 (12)
C5ⁱⁱ—K1—N1	80.70 (4)	O3—C2—K1^iv	61.45 (8)
O1ⁱ—K1—C2ⁱⁱⁱ	97.99 (4)	O4—C2—K1^iv	135.44 (9)
O2ⁱⁱ—K1—C2ⁱⁱⁱ	98.10 (4)	C1—C2—K1^iv	83.41 (9)
O3ⁱ—K1—C2ⁱⁱⁱ	118.31 (4)	O4—C3—H3A	109.5
O1—K1—C2ⁱⁱⁱ	83.79 (3)	O4—C3—H3B	109.5
O2—K1—C2ⁱⁱⁱ	71.83 (3)	H3A—C3—H3B	109.5
O3ⁱⁱⁱ—K1—C2ⁱⁱⁱ	21.75 (3)	O4—C3—H3C	109.5
O1ⁱⁱⁱ—K1—C2ⁱⁱⁱ	53.27 (3)	H3A—C3—H3C	109.5
C5ⁱⁱ—K1—C2ⁱⁱⁱ	150.79 (4)	H3B—C3—H3C	109.5
N1—K1—C2ⁱⁱⁱ	73.06 (3)	C5—C4—C1	119.13 (14)
O1ⁱ—K1—N1ⁱⁱⁱ	120.52 (3)	C5—C4—C6	123.51 (14)
O2ⁱⁱ—K1—N1ⁱⁱⁱ	68.28 (3)	C1—C4—C6	117.33 (13)
O3ⁱ—K1—N1ⁱⁱⁱ	96.40 (3)	C5—C4—K1^v	66.48 (9)
O1—K1—N1ⁱⁱⁱ	125.11 (3)	C1—C4—K1^v	99.55 (9)
O2—K1—N1ⁱⁱⁱ	94.52 (3)	C6—C4—K1^v	105.93 (10)
O3ⁱⁱⁱ—K1—N1ⁱⁱⁱ	56.00 (3)	C4—C5—K1^v	90.11 (10)
O1ⁱⁱⁱ—K1—N1ⁱⁱⁱ	22.80 (3)	C4—C5—H5A	120.0
C5ⁱⁱ—K1—N1ⁱⁱⁱ	140.88 (4)	K1^v—C5—H5A	88.2
N1—K1—N1ⁱⁱⁱ	107.96 (4)	C4—C5—H5B	120.0
C2ⁱⁱⁱ—K1—N1ⁱⁱⁱ	43.50 (4)	K1^v—C5—H5B	91.7
O1ⁱ—K1—C4ⁱⁱ	115.12 (4)	H5A—C5—H5B	120.0
O2ⁱⁱ—K1—C4ⁱⁱ	51.13 (3)	C4—C6—H6A	109.5
O3ⁱ—K1—C4ⁱⁱ	89.44 (4)	C4—C6—H6B	109.5
O1—K1—C4ⁱⁱ	95.85 (4)	H6A—C6—H6B	109.5
O2—K1—C4ⁱⁱ	83.16 (3)	C4—C6—H6C	109.5
O3ⁱⁱⁱ—K1—C4ⁱⁱ	166.33 (3)	H6A—C6—H6C	109.5
O1ⁱⁱⁱ—K1—C4ⁱⁱ	124.33 (4)	H6B—C6—H6C	109.5
C5ⁱⁱ—K1—C4ⁱⁱ	23.41 (4)

O1ⁱ—K1—O1—N1	160.77 (10)	O1ⁱⁱⁱ—K1—N1—O1	−125.49 (9)
O2ⁱⁱ—K1—O1—N1	−35.71 (9)	C5ⁱⁱ—K1—N1—O1	77.40 (8)
O3ⁱ—K1—O1—N1	−178.51 (7)	C2ⁱⁱⁱ—K1—N1—O1	−115.56 (8)
O2—K1—O1—N1	−10.30 (7)	N1ⁱⁱⁱ—K1—N1—O1	−141.94 (7)
O3ⁱⁱⁱ—K1—O1—N1	81.97 (8)	C4ⁱⁱ—K1—N1—O1	97.17 (8)
O1ⁱⁱⁱ—K1—O1—N1	72.42 (10)	O1ⁱ—K1—N1—O2	−179.41 (8)
C5ⁱⁱ—K1—O1—N1	−98.01 (8)	O2ⁱⁱ—K1—N1—O2	−12.78 (9)
C2ⁱⁱⁱ—K1—O1—N1	60.23 (8)	O3ⁱ—K1—N1—O2	−158.75 (8)
N1ⁱⁱⁱ—K1—O1—N1	45.79 (8)	O1—K1—N1—O2	−161.15 (13)
C4ⁱⁱ—K1—O1—N1	−84.68 (8)	O3ⁱⁱⁱ—K1—N1—O2	105.08 (8)
O1ⁱ—K1—O1—K1ⁱ	0.0	O1ⁱⁱⁱ—K1—N1—O2	73.36 (8)
O2ⁱⁱ—K1—O1—K1ⁱ	163.52 (4)	C5ⁱⁱ—K1—N1—O2	−83.74 (8)
O3ⁱ—K1—O1—K1ⁱ	20.72 (6)	C2ⁱⁱⁱ—K1—N1—O2	83.29 (8)
O2—K1—O1—K1ⁱ	−171.07 (6)	N1ⁱⁱⁱ—K1—N1—O2	56.91 (9)
O3ⁱⁱⁱ—K1—O1—K1ⁱ	−78.80 (4)	C4ⁱⁱ—K1—N1—O2	−63.97 (8)
O1ⁱⁱⁱ—K1—O1—K1ⁱ	−88.35 (6)	O1ⁱ—K1—N1—C1	81.4 (3)
C5ⁱⁱ—K1—O1—K1ⁱ	101.21 (5)	O2ⁱⁱ—K1—N1—C1	−112.0 (3)
N1—K1—O1—K1ⁱ	−160.77 (10)	O3ⁱ—K1—N1—C1	102.0 (3)
C2ⁱⁱⁱ—K1—O1—K1ⁱ	−100.54 (4)	O1—K1—N1—C1	99.6 (4)
N1ⁱⁱⁱ—K1—O1—K1ⁱ	−114.98 (4)	O2—K1—N1—C1	−99.2 (3)
C4ⁱⁱ—K1—O1—K1ⁱ	114.55 (4)	O3ⁱⁱⁱ—K1—N1—C1	5.9 (3)
O1ⁱ—K1—O1—K1^iv	−91.64 (6)	O1ⁱⁱⁱ—K1—N1—C1	−25.9 (3)
O2ⁱⁱ—K1—O1—K1^iv	71.88 (6)	C5ⁱⁱ—K1—N1—C1	177.0 (3)
O3ⁱ—K1—O1—K1^iv	−70.93 (7)	C2ⁱⁱⁱ—K1—N1—C1	−15.9 (3)
O2—K1—O1—K1^iv	97.29 (7)	N1ⁱⁱⁱ—K1—N1—C1	−42.3 (4)
O3ⁱⁱⁱ—K1—O1—K1^iv	−170.45 (6)	C4ⁱⁱ—K1—N1—C1	−163.2 (3)
O1ⁱⁱⁱ—K1—O1—K1^iv	180.0	O1ⁱ—K1—N1—K1^iv	−56.32 (4)
C5ⁱⁱ—K1—O1—K1^iv	9.57 (6)	O2ⁱⁱ—K1—N1—K1^iv	110.31 (4)
N1—K1—O1—K1^iv	107.58 (10)	O3ⁱ—K1—N1—K1^iv	−35.66 (9)
C2ⁱⁱⁱ—K1—O1—K1^iv	167.82 (6)	O1—K1—N1—K1^iv	−38.06 (7)
N1ⁱⁱⁱ—K1—O1—K1^iv	153.38 (4)	O2—K1—N1—K1^iv	123.09 (9)
C4ⁱⁱ—K1—O1—K1^iv	22.91 (6)	O3ⁱⁱⁱ—K1—N1—K1^iv	−131.83 (4)
O1ⁱ—K1—O2—N1	0.66 (9)	O1ⁱⁱⁱ—K1—N1—K1^iv	−163.55 (3)
O2ⁱⁱ—K1—O2—N1	166.92 (9)	C5ⁱⁱ—K1—N1—K1^iv	39.34 (4)
O3ⁱ—K1—O2—N1	66.31 (19)	C2ⁱⁱⁱ—K1—N1—K1^iv	−153.62 (4)
O1—K1—O2—N1	10.16 (7)	N1ⁱⁱⁱ—K1—N1—K1^iv	180.0
O3ⁱⁱⁱ—K1—O2—N1	−71.65 (8)	C4ⁱⁱ—K1—N1—K1^iv	59.12 (4)
O1ⁱⁱⁱ—K1—O2—N1	−119.59 (8)	O1—N1—C1—C2	5.1 (2)
C5ⁱⁱ—K1—O2—N1	92.06 (8)	O2—N1—C1—C2	−174.70 (13)
C2ⁱⁱⁱ—K1—O2—N1	−89.27 (8)	K1—N1—C1—C2	−84.2 (4)
N1ⁱⁱⁱ—K1—O2—N1	−126.92 (9)	K1^iv—N1—C1—C2	55.71 (13)
C4ⁱⁱ—K1—O2—N1	115.38 (8)	O1—N1—C1—C4	−176.54 (12)
O1ⁱ—K1—O2—K1^v	−135.53 (5)	O2—N1—C1—C4	3.7 (2)
O2ⁱⁱ—K1—O2—K1^v	30.73 (5)	K1—N1—C1—C4	94.1 (3)
O3ⁱ—K1—O2—K1^v	−69.88 (17)	K1^iv—N1—C1—C4	−125.94 (12)
O1—K1—O2—K1^v	−126.03 (7)	O1—N1—C1—K1^iv	−50.60 (12)
O3ⁱⁱⁱ—K1—O2—K1^v	152.16 (5)	O2—N1—C1—K1^iv	129.60 (12)
O1ⁱⁱⁱ—K1—O2—K1^v	104.22 (5)	K1—N1—C1—K1^iv	−139.9 (3)
C5ⁱⁱ—K1—O2—K1^v	−44.14 (6)	K1ⁱ—O3—C2—O4	−153.88 (10)
N1—K1—O2—K1^v	−136.19 (11)	K1^iv—O3—C2—O4	128.14 (13)
C2ⁱⁱⁱ—K1—O2—K1^v	134.54 (6)	K1ⁱ—O3—C2—C1	25.9 (3)
N1ⁱⁱⁱ—K1—O2—K1^v	96.89 (5)	K1^iv—O3—C2—C1	−52.12 (17)
C4ⁱⁱ—K1—O2—K1^v	−20.81 (5)	K1ⁱ—O3—C2—K1^iv	77.98 (12)
K1ⁱ—O1—N1—O2	163.96 (11)	C3—O4—C2—O3	−2.9 (2)
K1—O1—N1—O2	18.87 (12)	C3—O4—C2—C1	177.36 (12)
K1^iv—O1—N1—O2	−119.37 (11)	C3—O4—C2—K1^iv	77.08 (17)
K1ⁱ—O1—N1—C1	−15.8 (2)	N1—C1—C2—O3	−11.9 (2)
K1—O1—N1—C1	−160.93 (12)	C4—C1—C2—O3	169.81 (15)
K1^iv—O1—N1—C1	60.82 (14)	K1^iv—C1—C2—O3	44.26 (15)
K1ⁱ—O1—N1—K1	145.09 (16)	N1—C1—C2—O4	167.86 (13)
K1^iv—O1—N1—K1	−138.24 (6)	C4—C1—C2—O4	−10.4 (2)
K1ⁱ—O1—N1—K1^iv	−76.67 (13)	K1^iv—C1—C2—O4	−135.97 (11)
K1—O1—N1—K1^iv	138.24 (6)	N1—C1—C2—K1^iv	−56.16 (13)
K1^v—O2—N1—O1	123.95 (10)	C4—C1—C2—K1^iv	125.55 (13)
K1—O2—N1—O1	−18.09 (12)	N1—C1—C4—C5	101.20 (18)
K1^v—O2—N1—C1	−56.24 (15)	C2—C1—C4—C5	−80.5 (2)
K1—O2—N1—C1	161.72 (11)	K1^iv—C1—C4—C5	11.4 (2)
K1^v—O2—N1—K1	142.04 (8)	N1—C1—C4—C6	−80.71 (18)
K1^v—O2—N1—K1^iv	49.79 (12)	C2—C1—C4—C6	97.62 (18)
K1—O2—N1—K1^iv	−92.25 (8)	K1^iv—C1—C4—C6	−170.51 (10)
O1ⁱ—K1—N1—O1	−18.26 (10)	N1—C1—C4—K1^v	32.88 (14)
O2ⁱⁱ—K1—N1—O1	148.37 (8)	C2—C1—C4—K1^v	−148.79 (12)
O3ⁱ—K1—N1—O1	2.40 (12)	K1^iv—C1—C4—K1^v	−56.92 (11)
O2—K1—N1—O1	161.15 (13)	C1—C4—C5—K1^v	−87.97 (13)
O3ⁱⁱⁱ—K1—N1—O1	−93.78 (8)	C6—C4—C5—K1^v	94.06 (15)

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

Experimental details

Crystal data
Chemical formula	K⁺·C₆H₈NO₄⁻
M_r	197.23
Crystal system, space group	Monoclinic, Cm2/c
Temperature (K)	100
a, b, c (Å)	23.9269 (13), 5.2909 (2), 14.2510 (7)
β (°)	113.361 (2)
V (Å³)	1656.21 (14)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.62
Crystal size (mm)	0.20 × 0.15 × 0.03

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	6264, 1810, 1416
R_int	0.041
(sin θ/λ)_max (Å⁻¹)	0.639

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.061, 1.01
No. of reflections	1810
No. of parameters	111
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.31, −0.27

Computer programs: COLLECT (Hooft, 1998), DENZO (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SCHAKAL99 (Keller, 1999), PLATON (Spek, 2009), publCIF (Westrip, 2010) and ORTEP (Davenport et al., 1999).

Selected bond lengths (Å) top

K1—O1ⁱ	2.7036 (10)	K1—O2	2.8896 (10)
K1—O2ⁱⁱ	2.7539 (11)	K1—O3ⁱⁱⁱ	2.8970 (12)
K1—O3ⁱ	2.7988 (11)	K1—O1ⁱⁱⁱ	2.9080 (11)
K1—O1	2.7994 (11)

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

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft (FG 806).

References

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