Refinement of the crystal structure of sodium hydrogen maleate trihydrate, NaH(C4H2O4) * 3H2O, at room temperature

Abstract

_C4H Source of material0.42 g (3.60 mmol) maleic acid was dissolved in 10 ml CH3OH/H2O (1:1 v/v) and then 1.0 ml (1 M) Na 2 C0 3 was added dropwise. The resulting solution (pH = 2.3) was allowed to stand at room temperature. Colorless needle-like crystals were grown by slow evaporation for several weeks. DiscussionNearly three decades ago, the crystal structure of sodium hydrogen maleate trihydrate was partially established by Gupta and coworkers using the photographic X-ray diffraction data collected at room temperature, but unfortunately hydrogen atoms were not located [ 1 ]. The structure was later refined at 120 Κ by Olovsson et al. [2]. In order to gain further insight into the nature of the possible intramolecular asymmetric hydrogen bonds, it was necessary to redetermine the crystal structure of Na(C4H304) · 3H2O by using accurate X-ray diffraction data at room temperature.In the crystal structure of the title compound, the hydrogen maleate (HOO(CH)2COO~) anions exhibit strong intramolecular asymmetric hydrogen bonds between two crystallographically distinct Ο atoms, namely 02 and 04, with J(02-04) = 2.442(2) Ä, Z02-H-04 = 173°. Such asymmetric hydrogen bonds are considerably shorter than those reported for symmetric hydrogen bonds, which are in general shorter than asymmetric ones [3,4]. In comparison with the respective ί/iso values of 0.0376(6) A 2 and 0.0369(3) A 2 for the associated 02 and 04 atoms, the reasonable Uho values of0.067(7) A 2 for the Η atom suggests that the present asymmetric hydrogen bonds are dynamically ordered. The short-* Correspondence author (e-mail: zhengcm@nbu.edu.cn) est CI-Ol bond (1.218(2) Ä) and longest CI-02 bond (1.300(2) A) indicate the double and single bond characters, respectively. The hydrogen atom is covalently bonded to the 02 atom (d(Ο-Η) = 1.00(2) A), which implies that the terminal containing CI atom belongs to the carboxylic group. For the carboxylate terminal, the C4-03 bond of 1.245(2) A is slightly shorter than that of 1.266(2) A to the 04 atom involved in the intramolecular hydrogen bond. The center C2-C3 bond of 1.329(2) A is significantly shorter than the remaining ones averaged at 1.494 A, indicating more double bond character. Owing to the fixation effect of the intramolecular hydrogen bonds, all atom s of the hydrogen maleate anion lie in a common plane. The Na + cations in the crystal structure are surrounded by six Ο atoms from five H2O molecules and one hydrogen maleate anion to form distorted NaOe octahedra with d(Na-O) = 2.380 A -2.476 A. Through two pairs of crystallographically equivalent bidentate bridging water Ο atoms, namely 05 and 07, the NaC>6 octahedra are edge shared resulting in one-dimensional (ID) J[Na(H20)^-H20)4/2(H00(CH) 2 C00)] chains along the [100] direction. Each Na atom has two close Na neighbors at 3.490( 1) A and 3.497(1) A, respectively. The formed ID chains are held into 2D layers parallel to (010) by linear interchain hydrogen bonds (</(06 03 (-*, -y, -z)) = 2.754 A, d(0b~04 (-x+1, -y, -z)) = 2.806 A, d(07-03 (x...

Predicting the Position of the Hydrogen Atom in the Short Intramolecular Hydrogen Bond of the Hydrogen Maleate Anion from Geometric Correlations

“…The compounds measured at the Bragg Institute are (in the order from symmetric to asymmetric, together with the abbreviation used throughout the manuscript, the chemical formula, the reference to the figures where the neutron-derived structures are depicted, and the references to previous X-ray and neutron structure determinations): potassium hydrogen maleate ( K , K­[C 4 H 3 O 4 ], Figure a ,,,− ); l -phenylalaninium hydrogen maleate ( PhAla , [C 9 H 12 NO 2 ]­[C 4 H 3 O 4 ], Figure b , ); barium bis­(hydrogen maleate) tetrahydrate ( Ba , Ba­[C 4 H 3 O 4 ] 2 ·4H 2 O), four independent hydrogen maleate anions in the asymmetric unit labeled 1 Ba to 4 Ba with different degrees of symmetry/asymmetry, Figure c); magnesium bis­(hydrogen maleate) hexahydrate ( Mg , Mg­[C 4 H 3 O 4 ] 2 ·6H 2 O, Figure d , ); 4-aminopyridinium hydrogen maleate ( 4AP , [C 5 H 7 N 2 ]­[C 4 H 3 O 4 ], Figure e); calcium bis­(hydrogen maleate) pentahydrate ( Ca , Ca­[C 4 H 3 O 4 ] 2 ·5H 2 O, Figure f , ); lithium hydrogen maleate dihydrate ( Li , Li­[C 4 H 3 O 4 ]·2H 2 O, Figure g , ); sodium hydrogen maleate trihydrate ( Na , Na­[C 4 H 3 O 4 ]·3H 2 O, Figure h ,− ); 8-hydroxyquinolinium hydrogen maleate ( 8HQ , [C 9 H 8 NO]­[C 4 H 3 O 4 ], Figure i). These hydrogen maleate salts span the whole range from perfectly symmetric (K) to highly asymmetric intramolecular O1–H1···O2 hydrogen bonds. The asymmetry in the 8HQ structure is the highest ever reported (Δ = 0.306 Å; Δ = d (O2···H1)– d (O1–H1)).…”

Structural Variety of Alkali Hydrogen Maleates at High Pressure

“…Previously unknown structures were solved with Shelxt and subsequently refined with Shelxl, as incorporated in OLEX2 . Previously reported structures were used as initial models for the HP data refinement. − All non-hydrogen atoms in NaHMAL, NH 4 HMAL, and KHMAL were refined isotropically. In the case of LiHMAL, all non-hydrogen atoms were refined anisotropically.…”

“…This resonance-assisted hydrogen bond (RAHB) locks the ring in a rigid, planar cis conformation, with an estimated stabilization of 21.5(2) kcal/mol . The properties of this particular hydrogen bond have been the subject of extensive research, including X-ray − and neutron − diffraction and NMR, vibrational, , and photoelectron spectroscopies, as well as theoretical investigations. ,− This relatively simple system is used as a prototype for the hydrogen transfer processes in enzymatic reactions − and DNA intercalations by ortho -hydroxyaryl Schiff bases. , However, the features of this RAHB depend on the environment, including the effect of solvation by polar solvents. − …”

“…Peculiar cases of HMAL anions in the PRP conformation include mostly alkali metal and ammonium salts. Interestingly, most of these anions are isostructural (K, Rb, and NH 4 analogues) and contain very short, symmetric RAHB. ,, Alkali metals with smaller ionic radii, namely Na + and Li + , form, instead, PCP arrangements. , Incidentally, they crystallize as hydrated forms. The APP conformation is present in most of the HMALs, allowing for the formation of compact structures due to the good separation of electrostatically repelling fragments, i.e., negatively charged oxygens, which interact with the cations.…”

“…11,12,14 Alkali metals with smaller ionic radii, namely Na + and Li + , form, instead, PCP arrangements. 10,13 Incidentally, they crystallize as hydrated forms. The APP conformation is present in most of the HMALs, allowing for the formation of compact structures due to the good separation of electrostatically repelling fragments, i.e., negatively charged oxygens, which interact with the cations.…”