Potassium hydrogen trans-glutaconate monohydrate at 295, 245 and 40 K, and its rubidium analogue at 298 K

A centrosymmetric and short O—H...O hydrogen bond was found in isomorphic crystals of potassium hydrogen trans-glutaconate monohydrate (potassium hydrogen trans-pent-2-ene-1,5-dioate, K⁺·C₅H₅O₄⁻·H₂O), (I), and rubidium hydrogen trans-glutaconate monohydrate (rubidium hydrogen trans-pent-2-ene-1,5-dioate, Rb⁺·C₅H₅O₄⁻·H₂O), (II). The O...O distance at room temperature is 2.444 (3) Å in (I), and 2.417 (4) Å in (II). The O...O distance for (I) showed no significant decrease at low temperatures.

S1. Comment

In the crystals of sodium and ammonium hydrogen trans-glutaconates an asymmetric O—H···O hydrogen bond is formed between the carboxyl and carboxylate groups of neighboring anions (Taka & Kashino, 1999). We report here on a symmetric and short O—H···O hydrogen bond formed in potassium hydrogen trans-glutaconate monohydrate, (I). An effect of temperature on the O···O distance of the hydrogen bond has been examined for (I) by crystal structure determination at room and low temperatures. The structure of rubidium hydrogen monohydrate, (II), has been determined at room temperature to investigate the effect of chemical substitution. \sch

In (I), the carboxyl groups at both ends of the acid moiety are ionized with an equal probability of 0.5 (Fig. 1). A chain of the anions is formed along [1 1 1] by two O—H···O hydrogen bonds lying on inversion centers at (1/2, 0, 1) and (0, 1/2, 0) in a similar manner as found in ammonium hydrogen succinate (Hirano et al., 1996; Kashino et al., 1998) (Fig. 3; Table 2). The chains related by a translation along a c axis are linked by hydrogen bonds through a water molecule. A K⁺ cation is coordinated by five O atoms of the anions and two O atoms of the water molecules. The K⁺ cations related by the c translation are bridged by three O atoms (Table 1).

The structure of (II) is isomorphous with (I). The Rb⁺···O distances averaged for the first coordination sphere is longer by 0.12 Å compared with the K⁺···O distances in (I) (Tables 1 and 7). The O···O distances of the hydrogen bonds involving the water molecule in (II) are significantly shorter than those in (I) (Tables 2 and 8). The distances of O1···O1^x [symmetry code: (x) 1 - x, -y, 2 - z], 2.455 (5) Å and O4···O4^xi [symmetry code: (xi) -x, 1 - y, -z], 2.417 (4) Å, in (II) are also shorter than the corresponding distances in (I) at room temperature (Table 2).

DSC measurement for (I) showed a weak and broad endothermic peak [ΔH = 90 (10) J mol^-1] over 260 to 270 K in the heating step. An anomaly in the temperature dependence of the lattice constants was observed from 230 to 270 K corresponding to the result of the DSC measurement. However, the reflection data were not collected in this temperature range to avoid the crystal deterioration accompanied by the phase transition, and the nature of the phase transition was not elucidated. The structures at low temperatures could be refined only based on the same space group as that at room temperature. No structural anomaly was detected at low temperatures. Neither the systematic absences which might occur for a monoclinic centered lattice, nor the superstructure reflections which might occur after a second order phase transition were observed at 40 K.

In (I), the K⁺···O distances and O···O distances of the hydrogen bonds involving the water molecule decrease with a decrease in temperature. On the other hand, the temperature dependence of the O1···O1^x and O4···O4^xi distances is small (Tables 1–6), showing that any librational effects on these distances are small. The latter distance is one of the shortest for the hydrogen bonds in the acid salts of carboxylic acids (Misaki et al., 1986; Kalsbeek & Larsen, 1991).

Difference Fourier maps calculated at 295 and 40 K by including all refined atoms show peaks with residual electron densities of 0.29 and 0.20 e Å^-3, respectively, on the inversion center at (0, 1/2, 0) near O4. Least-squares refinements constrained the H atom position to the inversion center gave almost the same values for R, wR and S as the unconstrained refinements, and resulted in U_iso = 0.110 (10) and 0.15 (2) Ų for the H atom at 295 and 40 K, respectively, although the U_iso values are higher than those determined by the unconstrained refinements [0.016 (8) and 0.10 (2) Ų at 295 and 40 K, respectively]. This evidence suggests that the H atom involved in the hydrogen bond lie in a single-minimum potential well as confirmed for a symmetric hydrogen bond [O···O 2.4321 (8) Å at 136 K] in dimethylammonium hydro-bis(squarate) (Lin et al., 1994). There is a possibility that the H atom position obtained by the unconstrained refinements is shifted from the inversion center by an influence of the polarized electrons from O4.

Related literature

For related literature, see: Beurskens et al. (1992); Hirano et al. (1996); Kalsbeek & Larsen (1991); Kashino et al. (1998); Lin et al. (1994); Misaki et al. (1986); Taka & Kashino (1999).

S2. Experimental

Crystals of (I) and (II) were grown by evaporation at room temperature from aqueous solutions of trans-glutaconic acid and respective metal carbonates in molar ratio of 2:1. A preliminary examination showed that the lattice constants of (I) could be converted to a centered triclinic lattice with a = 13.021 (4), b = 15.018 (4), c = 4.068 (2) Å, α = 89.66 (3), β = 110.54 (4), γ = 90.34 (3) °, V = 744.9 (3) ų. The intensity distribution for the converted cell showed neither the Laue symmetry 2/m nor the systematic absences for a centered monoclinic lattice. Thus, the reflection data were collected based on the primitive triclinic lattice.

A crystal of (I) was sealed in a glass capillary for X-ray diffraction measurement at low temperatures. A thermocouple was fixed on the capillary adjacent to the crystal. The temperature was regulated within ±0.3 K using a closed-cycle He refrigerator (APD CRYOGENICS INC, HC-2) equipped with a temperature controller (CHINO, KP-1000). The cell constants were determined from 294 to 40 K from 24 reflections in 11.5 >θ > 10°. The X-ray diffraction data at low temperatures were collected at 45 and 245 K.

Difference scanning calorimetry (DSC) was carried out for (I) with the cooling and heating rates of 10 K min^-1 using a Perkin-Elmer DSC-7. The DSC curves were recorded in the range of 173 to 323 K.

S3. Refinement

The structure of (I) at 295 K was solved by a direct method (SIR92; Altmare et al., 1994). H atoms were located by difference Fourier maps and refined by assuming the isotropic displacement. Presence of the superstructure reflections was examined at 40 K by doubling the periods along the a, b and c axes, but no significant intensities were detected. The diffraction data at 40 K were collected based on the same lattice as that 295 K. The structure was refined by assuming the space group P 1. The refinement was converged to essentially the same structure as obtained at 295 K. An attempt to refine the structure in space group P 1 was made, but the refinement did not converge because of large parameter correlations. The structure at 245 K was refined in the same manner as at 40 K.

The structure of (II) was solved using an automated Patterson solution method (DIRDIF92 PATTY; Beurskens et al., 1992). The H atom attached to the carboxyl group of (II) was not found in a difference Fourier map, and it was not included in the refinement. The H atoms of the water molecules were refined isotropically. The other H atoms in (II) were fixed at the calculated positions, and their isotropic displacements were assumed to be 1.2 times of the equivalent displacements of the parent atoms.

Computing details

Data collection: MSC/AFC Diffractometer Control (Molecular Structure Corporation, 1990) for I295K; MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1990) for I245K, I40K, (II). Cell refinement: MSC/AFC Diffractometer Control for I295K; MSC/AFC Diffractometer Control Software for I245K, I40K, (II). Data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1997-1999) for I295K, (II); TEXSAN (Molecular Structure Corporation, 1997-1999) for I245K, I40K. Program(s) used to solve structure: SIR92 (Altomare et al., 1994) for I295K, I245K, I40K; DIRDIF92 PATTY (Beurskens, 1992) for (II). Program(s) used to refine structure: TEXSAN for Windows for I295K, (II); TEXSAN for I245K, I40K. Software used to prepare material for publication: TEXSAN for Windows for I295K, (II); TEXSAN for I245K, I40K.

Figures

	Fig. 1. ORTEP-3 (Farrugia, 1997) drawing at 295 K of the asymmetric unit of (I) with the atomic numbering. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii. The occupancy factor for the H5 and H6 atoms is 0.5.
	Fig. 2. ORTEP-3 (Farrugia, 1997) drawing of the asymmetric unit of (II) with the atomic numbering. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii. The H atom attached to the carboxyl group is not shown, because it was not found in a difference Fourier map.
	Fig. 3. Arrangement of the anion and coordination around the cation, drawn based on the atomic parameters of (I) at 295 K.

(I295K)

Crystal data

K(C5H5O4)·H2O	Z = 2
Mr = 186.21	F(000) = 192
Triclinic, P1	Dx = 1.660 Mg m^−3
a = 9.968 (3) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.909 (4) Å	Cell parameters from 25 reflections
c = 4.068 (2) Å	θ = 10.5–11.0°
α = 103.06 (4)°	µ = 0.69 mm^−1
β = 103.51 (4)°	T = 295 K
γ = 98.15 (3)°	Prismatic, colorless
V = 372.5 (3) Å^3	0.36 × 0.15 × 0.10 mm

Data collection

Rigaku AFC5R diffractometer	1658 reflections with I > 0.1σ(I)
Radiation source: Rigaku rotating anode	Rint = 0.018
Graphite monochromator	θmax = 27.5°, θmin = 2.1°
ω–2θ scans	h = −12→12
Absorption correction: ψ scans (North et al., 1968)	k = −5→12
Tmin = 0.901, Tmax = 0.934	l = −5→5
1807 measured reflections	3 standard reflections every 97 reflections
1707 independent reflections	intensity decay: none

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	0 constraints
R[F^2 > 2σ(F^2)] = 0.043	All H-atom parameters refined
wR(F^2) = 0.051	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + 0.00002|Fo|^2]
S = 1.70	(Δ/σ)max = 0.01
1658 reflections	Δρmax = 0.29 e Å^−3
132 parameters	Δρmin = −0.32 e Å^−3

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
K1	0.83891 (3)	0.18157 (4)	0.53989 (9)	0.03691 (10)
O1	0.43289 (11)	0.08620 (11)	0.9021 (3)	0.0431 (4)
O2	0.64535 (9)	0.19801 (10)	0.9211 (3)	0.0411 (3)
O3	0.05859 (9)	0.28947 (10)	0.2068 (3)	0.0363 (3)
O4	0.10468 (11)	0.52067 (11)	0.2465 (3)	0.0370 (3)
O5	0.15773 (13)	0.02248 (12)	0.0593 (3)	0.0436 (4)
C1	0.45259 (15)	0.30068 (15)	0.7397 (4)	0.0315 (4)
C2	0.32274 (14)	0.31722 (14)	0.7137 (4)	0.0268 (4)
C3	0.27018 (15)	0.44001 (15)	0.6163 (4)	0.0307 (4)
C4	0.51657 (14)	0.18803 (15)	0.8604 (4)	0.0297 (4)
C5	0.13272 (13)	0.40837 (14)	0.3341 (3)	0.0257 (4)
H1	0.5163 (14)	0.3660 (14)	0.692 (4)	0.039 (4)*
H2	0.2606 (13)	0.2522 (14)	0.766 (4)	0.037 (4)*
H3	0.3406 (14)	0.4963 (14)	0.553 (3)	0.038 (4)*
H4	0.2587 (14)	0.5024 (15)	0.812 (4)	0.045 (5)*
H5	0.465 (3)	0.026 (3)	0.938 (7)	0.022 (9)*	0.5000
H6	0.046 (3)	0.503 (3)	0.091 (7)	0.016 (8)*	0.5000
H7	0.1314 (17)	0.0959 (18)	0.123 (5)	0.058 (6)*
H8	0.2372 (19)	0.054 (2)	0.086 (5)	0.080 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
K1	0.0366 (2)	0.0397 (2)	0.0358 (2)	0.01238 (15)	0.00907 (14)	0.01098 (16)
O1	0.0272 (6)	0.0354 (7)	0.0775 (9)	0.0143 (5)	0.0131 (5)	0.0328 (6)
O2	0.0220 (5)	0.0494 (7)	0.0580 (7)	0.0141 (5)	0.0100 (5)	0.0234 (6)
O3	0.0306 (5)	0.0242 (6)	0.0479 (7)	0.0060 (5)	−0.0014 (5)	0.0097 (5)
O4	0.0349 (6)	0.0294 (6)	0.0442 (7)	0.0109 (5)	−0.0038 (6)	0.0176 (6)
O5	0.0321 (7)	0.0316 (7)	0.0645 (8)	0.0094 (6)	0.0134 (6)	0.0061 (6)
C1	0.0274 (8)	0.0297 (8)	0.0405 (9)	0.0052 (7)	0.0070 (7)	0.0187 (7)
C2	0.0260 (8)	0.0260 (8)	0.0304 (8)	0.0064 (6)	0.0061 (6)	0.0128 (7)
C3	0.0286 (8)	0.0269 (8)	0.0364 (9)	0.0069 (7)	0.0028 (7)	0.0137 (7)
C4	0.0259 (8)	0.0338 (8)	0.0320 (8)	0.0116 (7)	0.0074 (6)	0.0112 (7)
C5	0.0244 (7)	0.0283 (8)	0.0299 (8)	0.0118 (6)	0.0098 (6)	0.0122 (7)

Geometric parameters (Å, º)

K1—O2	2.7437 (17)	O4—C5	1.290 (2)
K1—O5^i	2.804 (2)	O4—H6	0.72 (3)
K1—O4^ii	2.814 (2)	O5—H7	0.82 (2)
K1—O2^iii	2.844 (2)	O5—H8	0.78 (2)
K1—O5^iv	2.869 (2)	C1—C2	1.311 (2)
K1—O3^v	2.924 (2)	C1—C4	1.482 (2)
K1—O3^vi	3.0250 (17)	C1—H1	0.926 (17)
K1—O1^iv	3.338 (3)	C2—C3	1.488 (2)
O1—C4	1.284 (2)	C2—H2	0.924 (16)
O1—H5	0.75 (3)	C3—C5	1.508 (3)
O2—C4	1.2343 (19)	C3—H3	0.953 (17)
O3—C5	1.225 (2)	C3—H4	0.93 (2)
O1···H8^vii	2.25 (2)	O4···H6^ix	1.73 (3)
O1···O1^viii	2.471 (3)	O4···O4^ix	2.444 (3)
O1···O5^vii	2.973 (2)	O4···C5^ix	3.207 (3)
O1···C4^viii	3.149 (3)	O4···C5^x	3.290 (3)
O1···H5^viii	1.74 (3)	O5···C2	3.376 (3)
O3···H7	2.13 (2)	C4···H5^viii	2.45 (3)
O3···O5	2.939 (2)	C5···H6^ix	2.57 (3)
O2—K1—O2^iii	93.42 (5)	K1^xi—O3—K1^xii	86.27 (5)
O2—K1—O3^vi	156.99 (4)	K1^i—O5—K1^iv	91.63 (6)
O2—K1—O3^v	87.47 (5)	C5—O4—H6	111 (3)
O2—K1—O4^ii	85.10 (5)	H7—O5—H8	99 (2)
O2—K1—O5^i	130.94 (6)	C2—C1—C4	126.70 (18)
O2—K1—O5^iv	67.97 (5)	C2—C1—H1	120.3 (11)
O2^iii—K1—O3^vi	83.75 (5)	C4—C1—H1	113.0 (11)
O2^iii—K1—O3^v	156.38 (4)	C1—C2—C3	123.15 (18)
O2^iii—K1—O4^ii	87.35 (6)	C1—C2—H2	119.5 (11)
O2^iii—K1—O5^i	67.53 (6)	C3—C2—H2	117.3 (11)
O2^iii—K1—O5^iv	132.44 (5)	C2—C3—C5	117.17 (16)
O3^vi—K1—O3^v	86.27 (5)	C2—C3—H3	110.1 (11)
O3^vi—K1—O4^ii	71.98 (5)	C2—C3—H4	110.4 (12)
O3^vi—K1—O5^i	68.82 (6)	C5—C3—H3	109.1 (11)
O3^vi—K1—O5^iv	129.42 (5)	C5—C3—H4	106.3 (12)
O3^v—K1—O4^ii	69.19 (6)	H3—C3—H4	102.6 (15)
O3^v—K1—O5^i	127.81 (6)	O1—C4—O2	123.89 (17)
O3^v—K1—O5^iv	69.42 (6)	O1—C4—C1	116.94 (16)
O4^ii—K1—O5^i	135.04 (6)	O2—C4—C1	119.16 (17)
O4^ii—K1—O5^iv	130.97 (6)	O3—C5—O4	125.17 (16)
O5^i—K1—O5^iv	91.63 (6)	O3—C5—C3	123.07 (16)
C4—O1—H5	115 (3)	O4—C5—C3	111.76 (16)
K1—O2—K1^vii	93.42 (5)
O1—C4—C1—C2	9.4 (3)	O4—C5—C3—C2	−173.48 (17)
O2—C4—C1—C2	−169.22 (19)	C1—C2—C3—C5	131.7 (2)
O3—C5—C3—C2	6.4 (3)	C3—C2—C1—C4	175.08 (18)

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z−1; (iv) −x+1, −y, −z+1; (v) x+1, y, z+1; (vi) x+1, y, z; (vii) x, y, z+1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z; (x) −x, −y+1, −z+1; (xi) x−1, y, z−1; (xii) x−1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H7···O3	0.82 (2)	2.13 (2)	2.939 (2)	171 (2)
O5—H8···O1^iii	0.78 (2)	2.25 (2)	2.973 (2)	153 (2)
O1—H5···O1^viii	0.75 (3)	1.74 (3)	2.471 (3)	167 (4)
O4—H6···O4^ix	0.72 (3)	1.73 (3)	2.444 (3)	172 (5)

Symmetry codes: (iii) x, y, z−1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z.

(I245K)

Crystal data

K(C5H5O4)·H2O	Z = 2
Mr = 186.21	F(000) = 192
Triclinic, P1	Dx = 1.683 Mg m^−3
a = 9.944 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.885 (2) Å	Cell parameters from 24 reflections
c = 4.0314 (8) Å	θ = 10.5–11.5°
α = 103.22 (2)°	µ = 0.69 mm^−1
β = 103.08 (2)°	T = 245 K
γ = 98.44 (2)°	Prismatic, colorless
V = 367.4 (3) Å^3	0.49 × 0.18 × 0.13 mm

Data collection

Huber offcenter four circle diffractometer	Rint = 0.041
Radiation source: Rigaku rotating anode	θmax = 33.0°, θmin = 2.0°
Graphite monochromator	h = −16→16
ω–2θ scans	k = −15→15
3039 measured reflections	l = 0→6
2709 independent reflections	3 standard reflections every 97 reflections
2455 reflections with I > 0.1σ(I)	intensity decay: none

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	0 constraints
R[F^2 > 2σ(F^2)] = 0.094	All H-atom parameters refined
wR(F^2) = 0.107	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo)]
S = 2.14	(Δ/σ)max = 0.03
2455 reflections	Δρmax = 0.95 e Å^−3
132 parameters	Δρmin = −0.90 e Å^−3

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
K1	0.83871 (6)	0.18053 (6)	0.53780 (16)	0.0250 (3)
O1	0.4327 (2)	0.0863 (2)	0.9065 (6)	0.0300 (9)
O2	0.64555 (18)	0.1988 (2)	0.9215 (5)	0.0288 (8)
O3	0.05710 (8)	0.28852 (18)	0.2069 (5)	0.0250 (8)
O4	0.1041 (2)	0.5212 (2)	0.2489 (5)	0.0256 (8)
O5	0.1587 (2)	0.0233 (2)	0.0649 (6)	0.0281 (8)
C1	0.4527 (3)	0.3020 (3)	0.7436 (7)	0.0228 (10)
C2	0.3221 (3)	0.3174 (3)	0.7174 (7)	0.0195 (9)
C3	0.2695 (3)	0.4409 (3)	0.6218 (7)	0.0219 (10)
C4	0.5165 (3)	0.1889 (3)	0.8648 (7)	0.0207 (9)
C5	0.1323 (3)	0.4089 (3)	0.3367 (6)	0.0189 (9)
H1	0.520 (3)	0.375 (3)	0.710 (8)	0.028 (8)*
H2	0.262 (3)	0.256 (3)	0.772 (8)	0.034 (9)*
H3	0.345 (3)	0.503 (3)	0.568 (7)	0.029 (8)*
H4	0.260 (3)	0.512 (3)	0.815 (9)	0.044 (9)*
H5	0.474 (5)	0.025 (5)	0.939 (13)	0.003 (12)*	0.5
H6	0.035 (8)	0.507 (9)	0.106 (19)	0.05 (2)*	0.5
H7	0.132 (3)	0.091 (3)	0.104 (8)	0.022 (8)*
H8	0.255 (4)	0.061 (3)	0.093 (9)	0.050 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
K1	0.0261 (3)	0.0279 (3)	0.0228 (3)	0.0094 (2)	0.0064 (2)	0.0085 (2)
O1	0.0190 (10)	0.0273 (10)	0.0521 (13)	0.0121 (8)	0.0099 (9)	0.0223 (10)
O2	0.0170 (9)	0.0359 (11)	0.0387 (12)	0.0113 (8)	0.0077 (8)	0.0167 (9)
O3	0.0232 (9)	0.0205 (9)	0.0306 (10)	0.0074 (8)	0.0020 (8)	0.0089 (8)
O4	0.0260 (11)	0.0199 (9)	0.0312 (11)	0.0087 (8)	−0.0000 (9)	0.0126 (8)
O5	0.0226 (11)	0.0227 (10)	0.0394 (12)	0.0087 (9)	0.0089 (9)	0.0062 (9)
C1	0.0181 (12)	0.0232 (13)	0.0297 (14)	0.0049 (10)	0.0059 (10)	0.0122 (11)
C2	0.0200 (12)	0.0196 (12)	0.0205 (12)	0.0061 (10)	0.0047 (10)	0.0085 (10)
C3	0.0218 (13)	0.0190 (12)	0.0268 (13)	0.0059 (10)	0.0043 (10)	0.0109 (11)
C4	0.0158 (11)	0.0266 (13)	0.0213 (12)	0.0078 (10)	0.0049 (9)	0.0077 (10)
C5	0.0190 (12)	0.0207 (12)	0.0228 (12)	0.0107 (10)	0.0093 (10)	0.0096 (10)

Geometric parameters (Å, º)

K1—O2	2.726 (2)	O4—C5	1.289 (3)
K1—O5^i	2.787 (2)	O4—H6	0.76 (7)
K1—O4^ii	2.808 (2)	O5—H7	0.75 (3)
K1—O2^iii	2.836 (2)	O5—H8	0.94 (3)
K1—O5^iv	2.845 (2)	C1—C2	1.313 (3)
K1—O3^v	2.913 (2)	C1—C4	1.486 (3)
K1—O3^vi	2.986 (2)	C1—H1	0.96 (3)
K1—O1^iv	3.319 (2)	C2—C3	1.491 (3)
O1—C4	1.282 (3)	C2—H2	0.88 (3)
O1—H5	0.80 (4)	C3—C5	1.510 (4)
O2—C4	1.236 (3)	C3—H3	0.99 (3)
O3—C5	1.236 (3)	C3—H4	0.95 (3)
O1···H8^vii	2.08 (3)	O4···H6^ix	1.69 (6)
O1···O1^viii	2.465 (4)	O4···O4^ix	2.443 (4)
O1···O5^vii	2.948 (3)	O4···C5^ix	3.207 (3)
O1···C4^viii	3.139 (3)	O4···C5^x	3.244 (3)
O1···H5^viii	1.68 (4)	O5···C2	3.346 (3)
O3···H7	2.18 (3)	C4···H5^viii	2.43 (4)
O3···O5	2.929 (3)	C5···H6^ix	2.53 (7)
O2—K1—O2^iii	92.88 (6)	K1^i—O5—K1^iv	91.41 (6)
O2—K1—O3^vi	156.41 (6)	C4—O1—H5	110 (4)
O2—K1—O3^v	87.40 (6)	C2—C1—C4	126.4 (2)
O2—K1—O4^ii	84.89 (6)	C2—C1—H1	120 (2)
O2—K1—O5^i	131.07 (6)	C4—C1—H1	114 (2)
O2—K1—O5^iv	68.61 (6)	C1—C2—C3	123.0 (2)
O2^iii—K1—O3^vi	84.02 (5)	C1—C2—H2	120 (2)
O2^iii—K1—O3^v	156.05 (6)	C3—C2—H2	117 (2)
O2^iii—K1—O4^ii	86.74 (6)	C2—C3—C5	117.2 (2)
O2^iii—K1—O5^i	67.93 (6)	C2—C3—H3	110 (2)
O2^iii—K1—O5^iv	132.60 (6)	C2—C3—H4	115 (2)
O3^vi—K1—O3^v	86.21 (5)	C5—C3—H3	111 (2)
O3^vi—K1—O4^ii	71.60 (6)	C5—C3—H4	106 (2)
O3^vi—K1—O5^i	69.13 (6)	H3—C3—H4	96 (2)
O3^vi—K1—O5^iv	129.27 (6)	C5—O4—H6	113 (7)
O3^v—K1—O4^ii	69.42 (6)	O1—C4—O2	123.9 (2)
O3^v—K1—O5^i	127.99 (6)	O1—C4—C1	117.1 (2)
O3^v—K1—O5^iv	69.42 (6)	O2—C4—C1	119.0 (2)
O4^ii—K1—O5^i	134.81 (6)	O3—C5—O4	124.8 (2)
O4^ii—K1—O5^iv	131.42 (6)	O3—C5—C3	123.1 (2)
O5^i—K1—O5^iv	91.41 (6)	O4—C5—C3	112.1 (2)
K1—O2—K1^vii	92.88 (6)	H7—O5—H8	100 (3)
K1^xi—O3—K1^xii	86.21 (5)
O1—C4—C1—C2	9.3 (4)	O4—C5—C3—C2	−173.3 (2)
O2—C4—C1—C2	−170.3 (3)	C1—C2—C3—C5	131.7 (3)
O3—C5—C3—C2	7.0 (4)	C3—C2—C1—C4	174.8 (2)

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z−1; (iv) −x+1, −y, −z+1; (v) x+1, y, z+1; (vi) x+1, y, z; (vii) x, y, z+1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z; (x) −x, −y+1, −z+1; (xi) x−1, y, z−1; (xii) x−1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H7···O3	0.75 (3)	2.18 (3)	2.929 (3)	178 (3)
O5—H8···O1^iii	0.94 (3)	2.08 (3)	2.948 (3)	153 (3)
O1—H5···O1^viii	0.80 (4)	1.68 (4)	2.465 (4)	169 (5)
O4—H6···O4^ix	0.76 (7)	1.69 (6)	2.443 (4)	172 (9)

Symmetry codes: (iii) x, y, z−1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z.

(I40K)

Crystal data

K(C5H5O4)·H2O	Z = 2
Mr = 186.21	F(000) = 192
Triclinic, P1	Dx = 1.703 Mg m^−3
a = 9.927 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.866 (2) Å	Cell parameters from 24 reflections
c = 4.0015 (8) Å	θ = 10.5–11.5°
α = 103.40 (1)°	µ = 0.70 mm^−1
β = 102.77 (2)°	T = 40 K
γ = 98.73 (2)°	Prismatic, colorless
V = 363.2 (3) Å^3	0.49 × 0.18 × 0.13 mm

Data collection

Huber off-center four circle diffractometer	Rint = 0.044
Radiation source: Rigaku rotating anode	θmax = 35.0°, θmin = 2.0°
Graphite monochromator	h = −16→16
ω–2θ scans	k = −15→15
3476 measured reflections	l = 0→6
3093 independent reflections	3 standard reflections every 97 reflections
2927 reflections with I > 0.1σ(I)	intensity decay: none

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	0 constraints
R[F^2 > 2σ(F^2)] = 0.069	All H-atom parameters refined
wR(F^2) = 0.085	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo)]
S = 2.01	(Δ/σ)max = 0.01
2927 reflections	Δρmax = 0.58 e Å^−3
132 parameters	Δρmin = −0.72 e Å^−3

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
K1	0.83838 (4)	0.17954 (4)	0.53441 (9)	0.00911 (10)
O1	0.43215 (12)	0.08640 (12)	0.9122 (3)	0.0117 (4)
O2	0.64621 (12)	0.20057 (12)	0.9220 (3)	0.0113 (4)
O3	0.05555 (12)	0.28770 (12)	0.2070 (3)	0.0104 (4)
O4	0.10295 (12)	0.52227 (12)	0.2524 (3)	0.0104 (4)
O5	0.15905 (13)	0.02478 (13)	0.0725 (3)	0.0117 (4)
C1	0.45286 (17)	0.30381 (16)	0.7482 (4)	0.0104 (5)
C2	0.32024 (16)	0.31766 (16)	0.7231 (4)	0.0087 (5)
C3	0.26907 (16)	0.44210 (16)	0.6286 (4)	0.0098 (5)
C4	0.51649 (16)	0.19023 (16)	0.8680 (4)	0.0085 (5)
C5	0.13116 (16)	0.40968 (16)	0.3404 (4)	0.0085 (5)
H1	0.519 (3)	0.381 (2)	0.716 (6)	0.020 (6)*
H2	0.257 (2)	0.255 (2)	0.779 (6)	0.012 (5)*
H3	0.343 (2)	0.507 (2)	0.574 (6)	0.013 (5)*
H4	0.256 (2)	0.510 (2)	0.825 (6)	0.017 (6)*
H5	0.466 (5)	0.023 (5)	0.943 (11)	0.004 (9)*	0.5
H6	0.041 (11)	0.484 (11)	0.06 (3)	0.10 (2)*	0.5
H7	0.131 (3)	0.099 (3)	0.133 (6)	0.017 (6)*
H8	0.245 (3)	0.063 (3)	0.081 (7)	0.029 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
K1	0.00824 (14)	0.01148 (14)	0.00898 (13)	0.00342 (10)	0.00192 (10)	0.00498 (10)
O1	0.0075 (5)	0.0112 (5)	0.0192 (6)	0.0039 (4)	0.0027 (4)	0.0093 (4)
O2	0.0064 (5)	0.0149 (5)	0.0140 (5)	0.0034 (4)	0.0020 (4)	0.0066 (4)
O3	0.0091 (5)	0.0105 (5)	0.0122 (5)	0.0029 (4)	0.0015 (4)	0.0054 (4)
O4	0.0097 (5)	0.0105 (5)	0.0120 (5)	0.0038 (4)	−0.0001 (4)	0.0067 (4)
O5	0.0088 (5)	0.0116 (5)	0.0149 (5)	0.0032 (4)	0.0027 (4)	0.0042 (4)
C1	0.0086 (6)	0.0108 (6)	0.0130 (7)	0.0026 (5)	0.0018 (5)	0.0067 (5)
C2	0.0086 (6)	0.0095 (6)	0.0090 (6)	0.0027 (5)	0.0015 (5)	0.0046 (5)
C3	0.0075 (6)	0.0102 (6)	0.0128 (6)	0.0028 (5)	0.0007 (5)	0.0067 (5)
C4	0.0076 (6)	0.0102 (6)	0.0081 (6)	0.0035 (5)	0.0012 (5)	0.0037 (5)
C5	0.0076 (6)	0.0115 (6)	0.0091 (6)	0.0044 (5)	0.0034 (5)	0.0056 (5)

Geometric parameters (Å, º)

K1—O2	2.7142 (13)	O4—C5	1.2917 (18)
K1—O5^i	2.7814 (14)	O4—H6	0.84 (10)
K1—O4^ii	2.7962 (13)	O5—H7	0.83 (3)
K1—O2^iii	2.8242 (14)	O5—H8	0.85 (3)
K1—O5^iv	2.8295 (13)	C1—C2	1.328 (2)
K1—O3^v	2.9043 (15)	C1—C4	1.489 (2)
K1—O3^vi	2.9498 (13)	C1—H1	0.98 (3)
K1—O1^iv	3.2949 (16)	C2—C3	1.494 (2)
O1—C4	1.2925 (19)	C2—H2	0.93 (2)
O1—H5	0.80 (4)	C3—C5	1.519 (2)
O2—C4	1.2419 (18)	C3—H3	0.98 (2)
O3—C5	1.2440 (19)	C3—H4	0.95 (2)
O1···H8^vii	2.11 (3)	O4···H6^ix	1.66 (9)
O1···O1^viii	2.460 (2)	O4···O4^ix	2.438 (2)
O1···O5^vii	2.929 (2)	O4···C5^x	3.186 (2)
O1···C4^viii	3.134 (2)	O4···C5^ix	3.202 (2)
O1···H5^viii	1.70 (4)	O5···C2	3.310 (2)
O3···H7	2.09 (3)	C4···H5^viii	2.41 (4)
O3···O5	2.9121 (17)	C5···H6^ix	2.58 (9)
O2—K1—O2^iii	92.50 (4)	K1^i—O5—K1^iv	90.98 (4)
O2—K1—O3^vi	155.65 (4)	C4—O1—H5	115 (4)
O2—K1—O3^v	87.04 (4)	C5—O4—H6	100 (7)
O2—K1—O4^ii	84.58 (4)	C2—C1—C4	125.86 (14)
O2—K1—O5^i	131.57 (4)	C2—C1—H1	118.1 (15)
O2—K1—O5^iv	69.48 (4)	C4—C1—H1	115.5 (15)
O2^iii—K1—O3^vi	84.18 (4)	C1—C2—C3	121.97 (14)
O2^iii—K1—O3^v	155.53 (4)	C1—C2—H2	121.7 (15)
O2^iii—K1—O4^ii	86.03 (4)	C3—C2—H2	116.2 (14)
O2^iii—K1—O5^i	68.64 (4)	C2—C3—C5	116.91 (13)
O2^iii—K1—O5^iv	132.99 (4)	C2—C3—H3	112.1 (13)
O3^vi—K1—O3^v	86.24 (4)	C2—C3—H4	114.2 (14)
O3^vi—K1—O4^ii	71.15 (4)	C5—C3—H3	109.9 (13)
O3^vi—K1—O5^i	69.34 (4)	C5—C3—H4	104.6 (14)
O3^vi—K1—O5^iv	128.93 (4)	H3—C3—H4	97.1 (18)
O3^v—K1—O4^ii	69.57 (4)	O1—C4—O2	123.86 (14)
O3^v—K1—O5^i	128.03 (4)	O1—C4—C1	117.33 (13)
O3^v—K1—O5^iv	69.36 (4)	O2—C4—C1	118.80 (14)
O4^ii—K1—O5^i	134.57 (4)	O3—C5—O4	124.73 (14)
O4^ii—K1—O5^iv	131.94 (4)	O3—C5—C3	122.96 (13)
O5^i—K1—O5^iv	90.98 (4)	O4—C5—C3	112.30 (13)
K1—O2—K1^vii	92.50 (4)	H7—O5—H8	99 (4)
K1^xi—O3—K1^xii	86.24 (4)
O1—C4—C1—C2	8.6 (2)	O4—C5—C3—C2	−173.51 (13)
O2—C4—C1—C2	−170.91 (15)	C1—C2—C3—C5	131.90 (16)
O3—C5—C3—C2	6.4 (2)	C3—C2—C1—C4	174.88 (14)

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z−1; (iv) −x+1, −y, −z+1; (v) x+1, y, z+1; (vi) x+1, y, z; (vii) x, y, z+1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z; (x) −x, −y+1, −z+1; (xi) x−1, y, z−1; (xii) x−1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H7···O3	0.83 (3)	2.09 (3)	2.9121 (17)	171 (2)
O5—H8···O1^iii	0.85 (3)	2.11 (3)	2.929 (2)	157 (2)
O1—H5···O1^viii	0.80 (4)	1.70 (4)	2.460 (2)	167 (5)
O4—H6···O4^ix	0.84 (10)	1.66 (9)	2.438 (2)	154 (10)

Symmetry codes: (iii) x, y, z−1; (viii) −x+1, −y, −z+2; (ix) −x, −y+1, −z.

(II)

Crystal data

Rb(C5H5O4)·H2O	Z = 2
Mr = 232.58	F(000) = 228
Triclinic, P1	Dx = 1.951 Mg m^−3
a = 10.015 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.988 (4) Å	Cell parameters from 25 reflections
c = 4.2432 (15) Å	θ = 10.9–11.4°
α = 101.50 (3)°	µ = 6.22 mm^−1
β = 104.41 (3)°	T = 298 K
γ = 97.29 (3)°	Prismatic, colorless
V = 395.8 (3) Å^3	0.50 × 0.30 × 0.25 mm

Data collection

Rigaku AFC5R diffractometer	1710 reflections with I > 0.1σ(I)
Radiation source: Rigaku rotating anode	Rint = 0.030
Graphite monochromator	θmax = 27.5°, θmin = 2.1°
ω–2θ scans	h = −5→12
Absorption correction: ψ scans (North et al., 1968)	k = −12→12
Tmin = 0.115, Tmax = 0.211	l = −5→5
1927 measured reflections	3 standard reflections every 97 reflections
1821 independent reflections	intensity decay: none

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	4 constraints
R[F^2 > 2σ(F^2)] = 0.054	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.052	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + 0.00002|Fo|^2]
S = 1.57	(Δ/σ)max = 0.03
1710 reflections	Δρmax = 0.62 e Å^−3
108 parameters	Δρmin = −0.91 e Å^−3

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

	x	y	z	Uiso*/Ueq
Rb1	0.84409 (3)	0.17393 (3)	0.54479 (8)	0.03743 (9)
O1	0.43422 (18)	0.0880 (2)	0.9104 (5)	0.0456 (7)
O2	0.64277 (18)	0.1956 (2)	0.9215 (5)	0.0461 (7)
O3	0.06299 (18)	0.29397 (19)	0.2205 (5)	0.0372 (6)
O4	0.10164 (17)	0.52079 (17)	0.2397 (5)	0.0391 (6)
O5	0.1621 (2)	0.0377 (3)	0.0478 (6)	0.0465 (8)
C1	0.4529 (3)	0.3028 (3)	0.7541 (7)	0.0364 (9)
C2	0.3233 (3)	0.3207 (3)	0.7201 (7)	0.0314 (8)
C3	0.2676 (3)	0.4426 (3)	0.6214 (7)	0.0355 (9)
C4	0.5152 (3)	0.1880 (3)	0.8671 (7)	0.0332 (9)
C5	0.1334 (3)	0.4113 (3)	0.3399 (7)	0.0280 (8)
H1	0.513	0.371	0.695	0.044*
H2	0.258	0.250	0.758	0.037*
H3	0.339	0.497	0.560	0.043*
H4	0.252	0.500	0.817	0.043*
H7	0.142 (3)	0.102 (3)	0.099 (7)	0.010 (8)*
H8	0.272 (4)	0.072 (4)	0.073 (9)	0.102 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Rb1	0.04161 (18)	0.03534 (17)	0.03623 (17)	0.00800 (12)	0.01146 (13)	0.00950 (12)
O1	0.0275 (11)	0.0380 (13)	0.0809 (16)	0.0123 (9)	0.0156 (11)	0.0318 (12)
O2	0.0274 (12)	0.0521 (14)	0.0647 (15)	0.0140 (10)	0.0127 (11)	0.0234 (12)
O3	0.0359 (12)	0.0242 (12)	0.0481 (13)	0.0071 (9)	0.0028 (10)	0.0114 (10)
O4	0.0441 (12)	0.0236 (11)	0.0478 (13)	0.0129 (9)	0.0009 (10)	0.0156 (10)
O5	0.0437 (15)	0.0315 (15)	0.0663 (17)	0.0124 (12)	0.0203 (12)	0.0066 (13)
C1	0.0287 (17)	0.0358 (18)	0.049 (2)	0.0077 (14)	0.0079 (14)	0.0221 (15)
C2	0.0321 (17)	0.0258 (16)	0.0362 (18)	0.0054 (13)	0.0038 (14)	0.0145 (14)
C3	0.0339 (17)	0.0292 (16)	0.0430 (19)	0.0088 (13)	0.0030 (14)	0.0162 (15)
C4	0.0283 (18)	0.0384 (19)	0.0340 (18)	0.0132 (15)	0.0085 (14)	0.0075 (15)
C5	0.0283 (16)	0.0300 (17)	0.0312 (17)	0.0128 (14)	0.0118 (13)	0.0110 (14)

Geometric parameters (Å, º)

Rb1—O2	2.871 (3)	O4—C5	1.297 (4)
Rb1—O5^i	2.927 (3)	C1—C2	1.308 (4)
Rb1—O4^ii	2.941 (3)	C1—C4	1.479 (5)
Rb1—O2^iii	2.965 (3)	C2—C3	1.493 (4)
Rb1—O5^iv	2.990 (3)	C3—C5	1.509 (4)
Rb1—O3^v	3.049 (3)	O5—H7	0.71 (3)
Rb1—O3^vi	3.103 (3)	O5—H8	1.08 (4)
Rb1—O1^iv	3.435 (3)	C1—H1	0.96
O1—C4	1.277 (4)	C2—H2	0.97
O2—C4	1.230 (4)	C3—H3	0.96
O3—C5	1.226 (4)	C3—H4	0.97
O1···O1^vii	2.455 (5)	O3···O5	2.887 (4)
O1···O5^viii	2.929 (4)	O4···O4^ix	2.417 (4)
O1···C4^vii	3.147 (5)	O4···C5^ix	3.200 (4)
O1···H8^viii	1.92 (4)	O4···C5^x	3.346 (4)
O3···H7	2.18 (3)	O5···C2	3.474 (5)
O2—Rb1—O2^iii	93.26 (8)	Rb1—O2—Rb1^viii	93.26 (8)
O2—Rb1—O3^vi	153.86 (7)	Rb1^xi—O3—Rb1^xii	87.20 (7)
O2—Rb1—O3^v	85.22 (8)	Rb1^i—O5—Rb1^iv	91.64 (9)
O2—Rb1—O4^ii	83.04 (7)	C2—C1—C4	126.8 (3)
O2—Rb1—O5^i	129.51 (8)	C2—C1—H1	116
O2—Rb1—O5^iv	66.80 (8)	C4—C1—H1	117
O2^iii—Rb1—O3^vi	82.70 (7)	C1—C2—C3	124.6 (3)
O2^iii—Rb1—O3^v	153.72 (7)	C1—C2—H2	119
O2^iii—Rb1—O4^ii	88.06 (8)	C3—C2—H2	117
O2^iii—Rb1—O5^i	66.43 (8)	C2—C3—C5	116.7 (3)
O2^iii—Rb1—O5^iv	130.92 (8)	C2—C3—H3	108
O3^vi—Rb1—O3^v	87.20 (7)	C2—C3—H4	108
O3^vi—Rb1—O4^ii	71.06 (7)	C5—C3—H3	109
O3^vi—Rb1—O5^i	72.31 (8)	C5—C3—H4	108
O3^vi—Rb1—O5^iv	133.69 (8)	O1—C4—O2	123.6 (3)
O3^v—Rb1—O4^ii	65.70 (7)	O1—C4—C1	118.2 (3)
O3^v—Rb1—O5^i	132.74 (8)	O2—C4—C1	118.2 (3)
O3^v—Rb1—O5^iv	72.25 (8)	O3—C5—O4	124.2 (3)
O4^ii—Rb1—O5^i	137.46 (8)	O3—C5—C3	122.8 (3)
O4^ii—Rb1—O5^iv	129.68 (8)	O4—C5—C3	113.0 (3)
O5^i—Rb1—O5^iv	91.64 (9)	H7—O5—H8	101 (3)
O1—C4—C1—C2	6.6 (6)	O4—C5—C3—C2	−171.6 (3)
O2—C4—C1—C2	−171.8 (4)	C1—C2—C3—C5	130.1 (4)
O3—C5—C3—C2	8.3 (5)	C3—C2—C1—C4	176.7 (4)

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z−1; (iv) −x+1, −y, −z+1; (v) x+1, y, z+1; (vi) x+1, y, z; (vii) −x+1, −y, −z+2; (viii) x, y, z+1; (ix) −x, −y+1, −z; (x) −x, −y+1, −z+1; (xi) x−1, y, z−1; (xii) x−1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H7···O3	0.71 (3)	2.18 (3)	2.886 (4)	175 (4)
O5—H8···O1^iii	1.08 (4)	1.92 (4)	2.929 (4)	154 (3)

Symmetry code: (iii) x, y, z−1.