Byproduct identification: crystal structure of potassium 2-eth­oxy-2-oxo­acetate

Creegan, S.E.; Ridenour, J.A.; Donnelly, R.J.; Kerr, A.T.

doi:10.1107/S205698902600914X

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Volume 82| Part 10| October 2026|

https://doi.org/10.1107/S205698902600914X

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Byproduct identification: crystal structure of potassium 2-ethoxy-2-oxoacetate

Shannon E. Creegan,^a James A. Ridenour,^b Robert J. Donnelly ^c and Andrew T. Kerr ^a ^*

^aUS Naval Research Laboratory, Center for Biomolecular Science and Engineering, 4555 Overlook Ave., SW Washington, DC 20375, USA, ^bUS Naval Research Laboratory, Materials Chemistry and Dynamics Branch, 4555 Overlook Ave., SW Washington, DC 20375, USA, and ^cDepartment of Chemistry, Washington College, 300 Washington Ave., Chestertown, MD 21620, USA
^*Correspondence e-mail: [email protected]

Edited by M. Weil, Vienna University of Technology, Austria (Received 2 August 2026; accepted 1 September 2026; online 8 September 2026)

Potassium 2-ethoxy-2-oxoacetate, K⁺·C₄H₅O₄⁻, was identified as a byproduct in the first step of synthesizing the shelf-stable salt potassium nitroacetonitrile (KNAN). A single crystal of the title salt was obtained by recrystallization of the ethanol filtrate resulting from the purification of the intended product salt, potassium ethyl nitrocyanoacetate. The asymmetric unit of K⁺·C₄H₅O₄⁻, contains a single potassium cation and a 2-ethoxy-2-oxoacetate anion, the ethyl group of which is disordered over two sets of sites in a 0.792 (13):0.208 (13) ratio. The packing is dictated primarily by K—O electrostatic interactions and comprises eight bonded oxygen atoms per cation, with distances ranging from 2.706 (2) to 3.053 (4) Å.

Keywords: crystal structure; byproduct identification; potassium oxalate-type salt; disorder.

CCDC reference: 2584812

1. Chemical context

Voinkov et al. (2016 ) reported an alternative synthesis method for the α-nitronitrile compound, nitroacetonitrile, C₂H₂N₂O₂ (NAN). This synthesis was developed to bypass the greatest hazard of NAN synthesis, spontaneous explosion (Thomas, 2009 ), while improving the yield and purity of the NAN produced. The final product of the reaction detailed by Voinkov et al. (2016) is the potassium salt of nitroacetonitrile (KNAN). Two key features of KNAN are its shelf-stability and that, as a salt, it is ready for immediate use in contrast to neutral NAN, which is unstable, requires careful storage, and needs to be deprotonated prior to use. The shelf-stable KNAN is produced in a two-step synthesis from ethyl (hydroxyimino)cyanoacetate. During the first step of this process, ethyl (hydroxyimino)cyanoacetate is oxidized with potassium permanganate in the presence of potassium hydroxide to form the salt potassium ethyl nitrocyanoacetate in 63% yield (Fig. 1). It was in executing this first step that we identified the salt potassium 2-ethoxy-2-oxoacetate, the crystal structure of which is reported here.

Figure 1
Synthesis scheme for the potassium salt of ethyl nitrocyanoacetate.

2. Structural commentary

The asymmetric unit of the title compound contains a single potassium cation and an anion, the ethyl fragment of which is disordered in a 0.792 (13):0.208 (13) ratio (Fig. 2). All bond lengths are in expected ranges when compared to similar potassium oxalate salt structures. The dihedral angle between the carboxy groups was determined to be 15.2 (6)°. The observed packing interactions (Fig. 3) of this polymeric salt structure are primarily electrostatic interactions between the potassium ion and the oxygen atoms of the 2-ethoxy-2-oxoacetate anion. These distances between potassium and oxygen range from 2.706 (2) to 3.053 (4) Å in length (see Table 1 for all K—O bonds).

Table 1
Selected bond lengths (Å)

K1—O1	2.706 (2)	K1—O1^iv	2.855 (3)
K1—O2ⁱ	2.712 (2)	K1—O4ⁱⁱ	3.008 (3)
K1—O1ⁱⁱ	2.741 (2)	K1—O2^iv	3.041 (3)
K1—O2ⁱⁱⁱ	2.828 (3)	K1—O3ⁱⁱⁱ	3.053 (4)
Symmetry codes: (i) ; (ii) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iv) .

Figure 2
The asymmetric unit showing the potassium cation and the disordered 2-ethoxy-2-oxoacetate anion. Displacement ellipsoids are drawn at the 50% probability level; bonds lengths are detailed in green.

Figure 3
Ball-and-stick representation of the packing of 2-ethoxy-2-oxoacetate molecules and potassium cations viewed down [010]. Several K—O distances are noted with black dotted lines.

Taking into account K—O distances of less than 3.0 Å, the oxygen atoms arrange in form of a distorted square pyramid around K⁺, as represented by a purple polyhedron in Fig. 4. The extended structure reveals the formation of potassium-oxygen chains propagating parallel to [001] (Figs. 4, 5). Within a distance of 3.05 Å, atom O1 binds in a μ₃-mode to three potassium ions while O2 interacts with two cations (Fig. 6). In contrast, both O3 and O4 only interact with one potassium ion each, and at longer distances (Table 1).

Figure 4
Ball-and-stick representation showing the distorted square-pyramidal coordination environment around the potassium cation as a purple polyhedron.

Figure 5
Ball and stick model of the extended structure of the title salt, showing the formation of potassium–oxygen chains propagating along [001] in polyhedral representation.

Figure 6
Interactions of O1 and O2 with potassium cations.

3. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.46; Groom et al., 2016 ) yielded entries containing either 2-ethoxy-2-oxoacetate bound to a metal or containing oxalate moieties bound to potassium as either a backbone structure or a metal coordinating ligand (Fig. 7). The most similar structures found were K_0.53(NH₄)_0.47(H₂C₂O₄)((HC₂O₄)H₂O)₂ (refcode ZAXLOB; Hamdouni et al., 2011 ) and [Cu(EtOOC–COO)₂(Hpz)₄] (MUVFIT; Garau et al., 2010 ). The ZAXLOB structure contains both oxalic acid and the hydrogenoxalate anion bound to potassium ions with K—O interaction distances from 2.900 to 2.920 Å. MUVFIT contains two 2-ethoxy-2-oxoacetate units bound to copper(II) through a single oxygen per unit at 2.359 Å, a closer distance than any found in either the title structure or ZAXLOB structure to the potassium ion. An additional five CSD entries were found containing any metal bound to an oxalate group where a single oxygen atom is bonded to a methyl or tert-butyl group with another two entries having metal bound to oxalate where two oxygen atoms are bonded to methyl groups. The bound metals include titanium (PUTRUV, Okumura et al., 2025 ), lithium (OXATIT and OXATOZ; Sun et al., 2021 ), iridium (IKUJII, Padilla et al., 2010 ; ILEZEE and ILEZII, Paneque et al., 2003 ), and osmium (UKEZUI, Lin et al., 2020 ).

Figure 7
Chemical structures of the compounds referenced in the database survey.

4. Synthesis and crystallization

A solution of KMnO₄ (11.85 g, 75 mmol) in water (200 ml) was added dropwise over 1 h to a warm solution of KOH (0.9 g, 16 mmol) and ethyl (hydroxyimino)cyanoacetate (7.15 g, 50.3 mmol) in water (140 ml). The solution was stirred overnight, until the KMnO₄ was fully consumed as shown by the depletion of the dark purple coloring in favor of black. The solution was filtered, removing the black colored solids, and the filtrate concentrated on a rotary evaporator, producing pale-yellow crystalline material. The solids were washed with ethanol and isolated by filtration. The yellow filtrate was stored overnight in a refrigerator and additional material precipitated. From this precipitate, a crystal of the salt potassium 2-ethoxy-2-oxoacetate was isolated for single-crystal X-ray diffraction. Comparison of the calculated pattern to the experimental powder pattern of bulk material collected showed both the byproduct potassium 2-ethoxy-2-oxoacetate and potassium ethyl nitrocyanoacetate present, next to some unassigned reflections (Fig. 8).

Figure 8
XRD pattern of isolated bulk material with comparison to the calculated pattern of the byproduct potassium 2-ethoxy-2-oxoacetate (red) and the intended product potassium ethyl nitrocyanoacetate (blue). XRD pattern plotted with DIFFRAC·EVA with X-offset of 0.09° to correct for sample height.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. A PART command in SHELXL (Sheldrick, 2015b ), accompanied by SIMU and RIGU restraints set to 0.01, were used to model the positional disorder within the ethyl group and resulted in a refined ratio of 0.792 (13):0.208 (2). Corresponding H atoms were included using a riding model for the methyl and methylene groups.

Table 2
Experimental details

Crystal data
Chemical formula	K⁺·C₄H₅O₄⁻
M_r	156.18
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	14.052 (2), 5.9280 (8), 8.0579 (10)
β (°)	93.242 (5)
V (Å³)	670.15 (16)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.73
Crystal size (mm)	0.12 × 0.09 × 0.02

Data collection
Diffractometer	Photon II CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.660, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	10487, 1593, 1192
R_int	0.059
(sin θ/λ)_max (Å⁻¹)	0.657

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.064, 0.150, 1.10
No. of reflections	1593
No. of parameters	103
No. of restraints	43
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.42, −0.31
Computer programs: APEX3 and SAINT (Bruker, 2019 ), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b), SHELXTL (Sheldrick, 2008 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2584812

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S205698902600914X/wm5809sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S205698902600914X/wm5809Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S205698902600914X/wm5809Isup3.cml

checkCIF report

Computing details top

Potassium 2-ethoxy-2-oxoacetate top

Crystal data top

K⁺·C₄H₅O₄⁻	F(000) = 320
M_r = 156.18	D_x = 1.548 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 14.052 (2) Å	Cell parameters from 1931 reflections
b = 5.9280 (8) Å	θ = 2.9–27.2°
c = 8.0579 (10) Å	µ = 0.73 mm⁻¹
β = 93.242 (5)°	T = 296 K
V = 670.15 (16) Å³	Plate, yellow
Z = 4	0.12 × 0.09 × 0.02 mm

Data collection top

Photon II CCD diffractometer	1593 independent reflections
Radiation source: 1uS 3.0 microfocus	1192 reflections with I > 2σ(I)
Helios multilayer optics monochromator	R_int = 0.059
φ and ω scans	θ_max = 27.9°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −17→18
T_min = 0.660, T_max = 0.746	k = −7→7
10487 measured reflections	l = −10→10

Refinement top

Refinement on F²	Primary atom site location: intrinsic phasing
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.064	H-atom parameters constrained
wR(F²) = 0.150	w = 1/[σ²(F_o²) + (0.0533P)² + 0.7606P] where P = (F_o² + 2F_c²)/3
S = 1.10	(Δ/σ)_max = 0.003
1593 reflections	Δρ_max = 0.42 e Å⁻³
103 parameters	Δρ_min = −0.30 e Å⁻³
43 restraints

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	Occ. (<1)
K1	0.09360 (6)	0.26080 (10)	0.61193 (8)	0.0455 (3)
O1	0.0930 (2)	0.5589 (4)	0.3575 (3)	0.0552 (7)
O2	0.1067 (2)	0.9317 (4)	0.3806 (3)	0.0650 (8)
O3	0.2563 (3)	0.9045 (6)	0.1792 (5)	0.0985 (12)
O4	0.2588 (2)	0.5356 (5)	0.2237 (4)	0.0761 (9)
C1	0.1325 (3)	0.7420 (5)	0.3364 (4)	0.0436 (8)
C2	0.2238 (3)	0.7407 (6)	0.2392 (5)	0.0552 (9)
C3	0.3425 (7)	0.521 (2)	0.1236 (14)	0.114 (3)	0.792 (13)
H3A	0.325405	0.450607	0.017359	0.137*	0.792 (13)
H3B	0.367178	0.670628	0.103228	0.137*	0.792 (13)
C4	0.4131 (6)	0.388 (2)	0.2152 (16)	0.144 (4)	0.792 (13)
H4A	0.467205	0.366411	0.149261	0.216*	0.792 (13)
H4B	0.386482	0.243678	0.241020	0.216*	0.792 (13)
H4C	0.432783	0.464288	0.316375	0.216*	0.792 (13)
C3A	0.376 (3)	0.547 (8)	0.198 (6)	0.122 (5)	0.208 (13)
H3AA	0.395966	0.686855	0.149019	0.147*	0.208 (13)
H3AB	0.414355	0.513027	0.298734	0.147*	0.208 (13)
C4A	0.369 (3)	0.362 (7)	0.083 (5)	0.125 (6)	0.208 (13)
H4AA	0.345767	0.416681	−0.024271	0.187*	0.208 (13)
H4AB	0.325420	0.251309	0.121351	0.187*	0.208 (13)
H4AC	0.430521	0.295372	0.074146	0.187*	0.208 (13)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
K1	0.0772 (6)	0.0234 (3)	0.0364 (4)	0.0041 (3)	0.0082 (3)	0.0011 (3)
O1	0.0809 (19)	0.0348 (12)	0.0516 (14)	−0.0030 (12)	0.0190 (13)	0.0021 (10)
O2	0.103 (2)	0.0317 (13)	0.0605 (17)	0.0068 (13)	0.0097 (16)	−0.0088 (11)
O3	0.103 (3)	0.068 (2)	0.128 (3)	−0.0207 (19)	0.040 (2)	0.016 (2)
O4	0.078 (2)	0.0634 (18)	0.089 (2)	0.0200 (15)	0.0244 (17)	0.0030 (16)
C1	0.069 (2)	0.0284 (14)	0.0332 (14)	0.0018 (15)	0.0006 (14)	−0.0003 (12)
C2	0.066 (2)	0.0461 (19)	0.053 (2)	−0.0061 (18)	0.0035 (18)	−0.0002 (16)
C3	0.074 (6)	0.145 (7)	0.125 (8)	0.045 (5)	0.029 (5)	0.008 (6)
C4	0.082 (6)	0.163 (8)	0.188 (10)	0.035 (6)	0.021 (6)	0.045 (8)
C3A	0.080 (10)	0.147 (10)	0.144 (12)	0.047 (9)	0.035 (9)	0.015 (10)
C4A	0.081 (12)	0.151 (12)	0.146 (13)	0.033 (11)	0.032 (11)	0.018 (12)

Geometric parameters (Å, º) top

K1—O1	2.706 (2)	O4—C3	1.465 (9)
K1—O2ⁱ	2.712 (2)	O4—C3A	1.67 (4)
K1—O1ⁱⁱ	2.741 (2)	C1—C2	1.540 (5)
K1—O2ⁱⁱⁱ	2.828 (3)	C3—C4	1.439 (12)
K1—O1^iv	2.855 (3)	C3—H3A	0.9700
K1—O4ⁱⁱ	3.008 (3)	C3—H3B	0.9700
K1—O2^iv	3.041 (3)	C4—H4A	0.9600
K1—O3ⁱⁱⁱ	3.053 (4)	C4—H4B	0.9600
K1—C1^iv	3.228 (4)	C4—H4C	0.9600
K1—C1ⁱⁱⁱ	3.485 (3)	C3A—C4A	1.44 (2)
K1—C1ⁱⁱ	3.513 (3)	C3A—H3AA	0.9700
K1—K1ⁱⁱ	4.0310 (5)	C3A—H3AB	0.9700
O1—C1	1.235 (4)	C4A—H4AA	0.9600
O2—C1	1.240 (4)	C4A—H4AB	0.9600
O3—C2	1.187 (5)	C4A—H4AC	0.9600
O4—C2	1.320 (4)

O1—K1—O2ⁱ	86.93 (8)	C1^iv—K1—K1ⁱⁱ	79.35 (6)
O1—K1—O1ⁱⁱ	176.99 (7)	C1ⁱⁱⁱ—K1—K1ⁱⁱ	61.12 (5)
O2ⁱ—K1—O1ⁱⁱ	90.11 (8)	C1ⁱⁱ—K1—K1ⁱⁱ	57.81 (5)
O1—K1—O2ⁱⁱⁱ	98.99 (7)	C1—O1—K1	134.1 (2)
O2ⁱ—K1—O2ⁱⁱⁱ	170.36 (12)	C1—O1—K1^v	119.2 (2)
O1ⁱⁱ—K1—O2ⁱⁱⁱ	84.01 (7)	K1—O1—K1^v	95.47 (7)
O1—K1—O1^iv	81.80 (8)	C1—O1—K1^iv	96.1 (2)
O2ⁱ—K1—O1^iv	115.28 (9)	K1—O1—K1^iv	98.20 (8)
O1ⁱⁱ—K1—O1^iv	98.99 (6)	K1^v—O1—K1^iv	111.19 (10)
O2ⁱⁱⁱ—K1—O1^iv	73.33 (8)	C1—O2—K1^vi	151.9 (2)
O1—K1—O4ⁱⁱ	125.26 (8)	C1—O2—K1^vii	111.8 (2)
O2ⁱ—K1—O4ⁱⁱ	72.80 (9)	K1^vi—O2—K1^vii	93.36 (7)
O1ⁱⁱ—K1—O4ⁱⁱ	54.12 (8)	C1—O2—K1^iv	87.2 (2)
O2ⁱⁱⁱ—K1—O4ⁱⁱ	97.56 (9)	K1^vi—O2—K1^iv	99.06 (9)
O1^iv—K1—O4ⁱⁱ	152.84 (8)	K1^vii—O2—K1^iv	103.70 (9)
O1—K1—O2^iv	107.27 (8)	C2—O3—K1^vii	107.6 (3)
O2ⁱ—K1—O2^iv	80.94 (9)	C2—O4—C3	114.9 (6)
O1ⁱⁱ—K1—O2^iv	71.67 (8)	C2—O4—C3A	110.5 (16)
O2ⁱⁱⁱ—K1—O2^iv	104.30 (6)	C2—O4—K1^v	106.3 (3)
O1^iv—K1—O2^iv	44.20 (7)	C3—O4—K1^v	115.5 (6)
O4ⁱⁱ—K1—O2^iv	118.32 (8)	O1—C1—O2	128.0 (4)
O1—K1—O3ⁱⁱⁱ	71.36 (10)	O1—C1—C2	117.4 (3)
O2ⁱ—K1—O3ⁱⁱⁱ	120.69 (9)	O2—C1—C2	114.6 (3)
O1ⁱⁱ—K1—O3ⁱⁱⁱ	110.74 (10)	O1—C1—K1^iv	61.6 (2)
O2ⁱⁱⁱ—K1—O3ⁱⁱⁱ	55.21 (9)	O2—C1—K1^iv	70.2 (2)
O1^iv—K1—O3ⁱⁱⁱ	115.07 (8)	C2—C1—K1^iv	156.9 (2)
O4ⁱⁱ—K1—O3ⁱⁱⁱ	76.63 (9)	O1—C1—K1^vii	139.1 (3)
O2^iv—K1—O3ⁱⁱⁱ	157.70 (8)	O2—C1—K1^vii	48.87 (17)
O1—K1—C1^iv	98.06 (8)	C2—C1—K1^vii	81.45 (18)
O2ⁱ—K1—C1^iv	100.99 (9)	K1^iv—C1—K1^vii	86.81 (8)
O1ⁱⁱ—K1—C1^iv	81.96 (8)	O1—C1—K1^v	42.90 (15)
O2ⁱⁱⁱ—K1—C1^iv	85.78 (8)	O2—C1—K1^v	151.4 (3)
O1^iv—K1—C1^iv	22.36 (7)	C2—C1—K1^v	81.02 (18)
O4ⁱⁱ—K1—C1^iv	134.99 (8)	K1^iv—C1—K1^v	86.35 (8)
O2^iv—K1—C1^iv	22.57 (6)	K1^vii—C1—K1^v	115.78 (9)
O3ⁱⁱⁱ—K1—C1^iv	135.50 (8)	O3—C2—O4	124.1 (4)
O1—K1—C1ⁱⁱⁱ	80.47 (7)	O3—C2—C1	123.6 (4)
O2ⁱ—K1—C1ⁱⁱⁱ	161.88 (9)	O4—C2—C1	112.2 (3)
O1ⁱⁱ—K1—C1ⁱⁱⁱ	102.53 (7)	C4—C3—O4	107.6 (8)
O2ⁱⁱⁱ—K1—C1ⁱⁱⁱ	19.29 (7)	C4—C3—H3A	110.2
O1^iv—K1—C1ⁱⁱⁱ	75.92 (8)	O4—C3—H3A	110.2
O4ⁱⁱ—K1—C1ⁱⁱⁱ	104.05 (9)	C4—C3—H3B	110.2
O2^iv—K1—C1ⁱⁱⁱ	115.18 (8)	O4—C3—H3B	110.2
O3ⁱⁱⁱ—K1—C1ⁱⁱⁱ	42.61 (9)	H3A—C3—H3B	108.5
C1^iv—K1—C1ⁱⁱⁱ	93.68 (9)	C3—C4—H4A	109.5
O1—K1—C1ⁱⁱ	159.67 (7)	C3—C4—H4B	109.5
O2ⁱ—K1—C1ⁱⁱ	74.27 (8)	H4A—C4—H4B	109.5
O1ⁱⁱ—K1—C1ⁱⁱ	17.87 (7)	C3—C4—H4C	109.5
O2ⁱⁱⁱ—K1—C1ⁱⁱ	98.69 (7)	H4A—C4—H4C	109.5
O1^iv—K1—C1ⁱⁱ	112.97 (8)	H4B—C4—H4C	109.5
O4ⁱⁱ—K1—C1ⁱⁱ	41.87 (8)	C4A—C3A—O4	91 (3)
O2^iv—K1—C1ⁱⁱ	77.81 (8)	C4A—C3A—H3AA	113.5
O3ⁱⁱⁱ—K1—C1ⁱⁱ	111.51 (10)	O4—C3A—H3AA	113.5
C1^iv—K1—C1ⁱⁱ	93.16 (8)	C4A—C3A—H3AB	113.5
C1ⁱⁱⁱ—K1—C1ⁱⁱ	115.79 (9)	O4—C3A—H3AB	113.5
O1—K1—K1ⁱⁱ	141.05 (6)	H3AA—C3A—H3AB	110.8
O2ⁱ—K1—K1ⁱⁱ	131.92 (6)	C3A—C4A—H4AA	109.5
O1ⁱⁱ—K1—K1ⁱⁱ	41.94 (5)	C3A—C4A—H4AB	109.5
O2ⁱⁱⁱ—K1—K1ⁱⁱ	42.18 (5)	H4AA—C4A—H4AB	109.5
O1^iv—K1—K1ⁱⁱ	82.75 (5)	C3A—C4A—H4AC	109.5
O4ⁱⁱ—K1—K1ⁱⁱ	74.10 (6)	H4AA—C4A—H4AC	109.5
O2^iv—K1—K1ⁱⁱ	85.18 (5)	H4AB—C4A—H4AC	109.5
O3ⁱⁱⁱ—K1—K1ⁱⁱ	83.42 (8)

K1—O1—C1—O2	−83.4 (5)	K1^vii—O2—C1—K1^v	−66.8 (5)
K1^v—O1—C1—O2	142.7 (3)	K1^iv—O2—C1—K1^v	36.9 (5)
K1^iv—O1—C1—O2	24.2 (4)	K1^vii—O3—C2—O4	151.2 (4)
K1—O1—C1—C2	98.6 (3)	K1^vii—O3—C2—C1	−25.4 (5)
K1^v—O1—C1—C2	−35.4 (4)	C3—O4—C2—O3	−0.5 (8)
K1^iv—O1—C1—C2	−153.8 (3)	C3A—O4—C2—O3	28.4 (19)
K1—O1—C1—K1^iv	−107.6 (3)	K1^v—O4—C2—O3	−129.6 (4)
K1^v—O1—C1—K1^iv	118.4 (2)	C3—O4—C2—C1	176.4 (6)
K1—O1—C1—K1^vii	−151.46 (18)	C3A—O4—C2—C1	−154.7 (18)
K1^v—O1—C1—K1^vii	74.6 (4)	K1^v—O4—C2—C1	47.4 (3)
K1^iv—O1—C1—K1^vii	−43.8 (3)	O1—C1—C2—O3	162.8 (4)
K1—O1—C1—K1^v	134.0 (4)	O2—C1—C2—O3	−15.6 (6)
K1^iv—O1—C1—K1^v	−118.4 (2)	K1^iv—C1—C2—O3	81.5 (7)
K1^vi—O2—C1—O1	81.6 (7)	K1^vii—C1—C2—O3	21.2 (4)
K1^vii—O2—C1—O1	−126.2 (3)	K1^v—C1—C2—O3	139.2 (4)
K1^iv—O2—C1—O1	−22.6 (4)	O1—C1—C2—O4	−14.2 (5)
K1^vi—O2—C1—C2	−100.3 (5)	O2—C1—C2—O4	167.5 (3)
K1^vii—O2—C1—C2	51.9 (4)	K1^iv—C1—C2—O4	−95.4 (6)
K1^iv—O2—C1—C2	155.5 (3)	K1^vii—C1—C2—O4	−155.7 (3)
K1^vi—O2—C1—K1^iv	104.1 (5)	K1^v—C1—C2—O4	−37.7 (3)
K1^vii—O2—C1—K1^iv	−103.65 (16)	C2—O4—C3—C4	132.1 (10)
K1^vi—O2—C1—K1^vii	−152.2 (6)	K1^v—O4—C3—C4	−103.5 (11)
K1^iv—O2—C1—K1^vii	103.65 (16)	C2—O4—C3A—C4A	−143 (3)
K1^vi—O2—C1—K1^v	141.0 (4)	K1^v—O4—C3A—C4A	5 (5)

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

Funding information

We would like to thank the Office of Naval Research (ONR) and the U·S. Naval Research Laboratory (NRL) for their generous support of this base 6.1 program.

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