Lithium phospho­enolpyruvate monohydrate at 85 K

The crystal structure of the title compound, lithium (1-carboxy­ethenyl­oxy)­phospho­nate monohydrate, Li⁺·C₃H₄O₆P^-·­H₂O, is governed by lithium-oxy­gen interactions and hydrogen bonds. The Li⁺ cation is tetrahedrally coordinated by phosphate and water O atoms. The phospho­enolpyruvate monoanions form carboxyl-to-carboxyl and phosphate-to-water hydrogen bonds.

S1. Comment

The phosphoenolpyruvate (PEP) plays an important biological role (Stryer, 1995). The geometrical details of the PEP derivatives as well as the effect of the protonation level and chemical environment on the PEP geometry were discussed earlier by Weichsel & Lis (1994) and Souhassou et al. (1996). We performed the X-ray structure determination of lithium phosphoenolpyruvate monohydrate, LiPEP·H₂O, (I) as a part of diffraction studies of charge density in crystals of the phosphoenolpyruvate derivatives. \sch

The crystals are composed of tetracoordinated Li⁺ cations, phosphoenolpyruvate monoanions and water of hydration. An ORTEP-3 (Johnson et al., 1997) view of the PEP fragment in the title monoanion is presented in Fig. 1. The enolpyruvate fragment is nearly planar and the enolic O4—C2 bond exhibits partly double-bond character what was also observed in other monoionized PEP systems (Weichsel & Lis, 1994). The length of the `high-energy' phosphate ester bond P—O4 is 1.6200 (3) Å, typical for monoionized PEP derivatives (Souhassou et al., 1996).

The phosphate and water O atoms form tetrahedral coordination around the lithium cation. The Li—O contacts range from 1.900 (1) to 2.021 (1) Å. Each O3 atom joins two centrosymmetrically related Li⁺ cations forming in this way an Li₂O₂ unit. A short distance between the Li⁺ cations in the four-membered ring [2.661 (2) Å] is also observed in other lithium derivatives. Furthermore, the O2 and O3 atoms from the phosphate group bridge two other centrosymmetrically related Li atoms forming an eight-membered ring with an Li···Li distance of 3.805 (2) Å. In this way, a (100) net is formed (Fig. 2).

The geometry of the hydrogen bonds is given in Table 2. Each carboxyl group participates in a hydrogen-bonded cyclic dimer around an inversion center creating in this way a two-dimensional network. The phosphate O1—H1 group takes part in the bond with water (O7) atom and the H71 water atom is utilized in bonding with the O2 from an adjacent anion, forming cyclic centrosymmetric systems of hydrogen bonds, so generating a three-dimensional structure.

S2. Experimental

Lithium phosphoenolpyruvate was prepared in a reaction of phosphoenolpyruvic acid with lithium carbonate in an aqueous environment. Crystals were obtained by slow evaporation from water at 277 K and afterwards ball-shaped by the solvent.

Computing details

Data collection: KUMA KM4 software (Kuma Diffraction, 1989); cell refinement: KUMA KM4 software; data reduction: KUMA KM4 software; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993); molecular graphics: ORTEP-3 (Johnson et al., 1997); software used to prepare material for publication: SHELXL93.

Figures

	Fig. 1. An ORTEP-3 (Johnson et al., 1997) view of the PEP fragment with a labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. Displacement parameters of hydrogen atoms were artificially diminished for clarity.
	Fig. 2. The packing diagram down the a axis showing part of the (100) net.

Lithium phosphoenolpyruvate monohydrate

Crystal data

Li(C3H4O6P)·H2O	Z = 2
Mr = 191.99	F(000) = 196
Triclinic, P1	Dx = 1.842 Mg m^−3
a = 5.2281 (7) Å	Mo Kα radiation, λ = 0.71073 Å
b = 5.5511 (7) Å	Cell parameters from 53 reflections
c = 12.009 (1) Å	θ = 7.5–17°
α = 94.59 (1)°	µ = 0.39 mm^−1
β = 90.36 (1)°	T = 85 K
γ = 94.91 (1)°	Ball, colourless
V = 346.10 (7) Å^3	0.55 × 0.55 × 0.55 mm

Data collection

Kuma KM4 diffractometer	Rint = 0.017
Radiation source: fine-focus sealed tube	θmax = 55.2°, θmin = 1.7°
Graphite monochromator	h = −12→0
ω/2θ scans	k = −12→12
8521 measured reflections	l = −27→27
8272 independent reflections	3 standard reflections every 100 reflections
6788 reflections with I > 2σ(I)	intensity decay: −6.2%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.026	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.079	All H-atom parameters refined
S = 1.16	Calculated w = 1/[σ^2(Fo^2) + (0.0444P)^2 + 0.0319P] where P = (Fo^2 + 2Fc^2)/3
8272 reflections	(Δ/σ)max = 0.058
133 parameters	Δρmax = 0.72 e Å^−3
0 restraints	Δρmin = −0.78 e Å^−3

Special details

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

Refinement. Refinement on F² for ALL reflections except for 0 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating Robs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
P	0.24334 (2)	0.66206 (2)	0.349743 (8)	0.00497 (2)
O1	0.51576 (5)	0.74931 (5)	0.30744 (3)	0.00913 (4)
O2	0.25895 (5)	0.42462 (5)	0.39807 (2)	0.00753 (3)
O3	0.12663 (5)	0.85963 (5)	0.41805 (2)	0.00772 (3)
O4	0.07495 (6)	0.58987 (5)	0.23644 (2)	0.00845 (4)
O5	−0.34631 (7)	0.79466 (6)	0.04209 (3)	0.01194 (5)
O6	−0.30060 (7)	0.42337 (6)	0.09748 (3)	0.01236 (5)
C1	−0.23540 (7)	0.64183 (7)	0.09994 (3)	0.00826 (4)
C2	−0.01437 (7)	0.75436 (6)	0.17003 (3)	0.00736 (4)
C3	0.07985 (8)	0.98338 (7)	0.16304 (3)	0.01013 (5)
Li	−0.0030 (2)	0.8215 (2)	0.56774 (9)	0.01014 (13)
O7	0.31092 (6)	0.78625 (6)	0.66211 (3)	0.00913 (4)
H1	0.565 (3)	0.905 (3)	0.3247 (16)	0.043 (5)*
H3	0.223 (3)	1.048 (2)	0.2035 (11)	0.019 (3)*
H31	−0.003 (3)	1.081 (2)	0.1107 (11)	0.018 (3)*
H5	−0.459 (3)	0.720 (3)	−0.0028 (12)	0.022 (3)*
H7	0.272 (3)	0.727 (3)	0.7206 (12)	0.023 (3)*
H71	0.442 (3)	0.714 (3)	0.6368 (12)	0.023 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P	0.00468 (3)	0.00414 (3)	0.00612 (3)	0.00045 (2)	0.00028 (2)	0.00049 (2)
O1	0.00663 (7)	0.00742 (8)	0.01310 (10)	−0.00066 (6)	0.00330 (6)	0.00044 (7)
O2	0.00724 (7)	0.00550 (7)	0.01018 (9)	0.00080 (5)	−0.00020 (6)	0.00251 (6)
O3	0.00897 (8)	0.00599 (7)	0.00843 (8)	0.00222 (6)	0.00200 (6)	0.00008 (6)
O4	0.01030 (8)	0.00637 (8)	0.00863 (8)	0.00064 (6)	−0.00337 (6)	0.00066 (6)
O5	0.01230 (10)	0.01067 (10)	0.01303 (11)	−0.00040 (7)	−0.00575 (8)	0.00398 (8)
O6	0.01375 (10)	0.00764 (9)	0.01534 (12)	−0.00003 (7)	−0.00649 (9)	0.00028 (8)
C1	0.00834 (10)	0.00838 (10)	0.00807 (10)	0.00072 (7)	−0.00155 (7)	0.00088 (8)
C2	0.00757 (9)	0.00734 (10)	0.00722 (10)	0.00066 (7)	−0.00067 (7)	0.00099 (7)
C3	0.01076 (11)	0.00834 (11)	0.01137 (12)	−0.00053 (8)	−0.00127 (9)	0.00283 (9)
Li	0.0104 (3)	0.0083 (3)	0.0119 (3)	0.0010 (2)	0.0015 (2)	0.0020 (3)
O7	0.00761 (8)	0.00793 (8)	0.01215 (10)	0.00135 (6)	0.00098 (7)	0.00188 (7)

Geometric parameters (Å, º)

P—O1	1.5657 (4)	C1—O6	1.2292 (5)
P—O2	1.4903 (3)	O1—H1	0.89 (2)
P—O3	1.4916 (3)	C3—H3	0.919 (13)
P—O4	1.6200 (3)	C3—H31	0.983 (13)
O4—C2	1.3685 (5)	O5—H5	0.852 (14)
C2—C1	1.4880 (5)	O7—H7	0.818 (14)
C2—C3	1.3327 (5)	O7—H71	0.868 (14)
C1—O5	1.3085 (5)
O1—P—O2	108.51 (2)	C2—C1—O5	114.00 (3)
O1—P—O3	111.59 (2)	C2—C1—O6	121.40 (3)
O1—P—O4	104.28 (2)	O5—C1—O6	124.59 (4)
O2—P—O3	118.43 (2)	P—O1—H1	115.1 (12)
O2—P—O4	103.19 (2)	C2—C3—H3	121.6 (8)
O3—P—O4	109.63 (2)	C2—C3—H31	118.4 (8)
P—O4—C2	124.28 (3)	H3—C3—H31	120.0 (11)
O4—C2—C1	110.68 (3)	C1—O5—H5	110.7 (9)
O4—C2—C3	127.08 (3)	H7—O7—H71	106.1 (14)
C3—C2—C1	122.22 (3)
O1—P—O4—C2	−74.39 (3)	O4—C2—C1—O5	173.81 (3)
O2—P—O4—C2	172.28 (3)	O4—C2—C1—O6	−7.11 (5)
O3—P—O4—C2	45.21 (4)	C3—C2—C1—O5	−7.91 (6)
P—O4—C2—C1	−158.78 (3)	C3—C2—C1—O6	171.17 (4)
P—O4—C2—C3	23.04 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H5···O6^i	0.85 (1)	1.78 (1)	2.634 (1)	177 (1)
O1—H1···O7^ii	0.89 (2)	1.78 (2)	2.655 (1)	171 (1)
O7—H71···O2^iii	0.87 (1)	1.84 (1)	2.699 (1)	172 (1)

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