Ammonium 2,7-di­methyl-5-bora-1,4,6,9-tetroxa­spiro­[4.4]­nonane-3,8-dionate (ammonium borodilactate)

In the title compound, NH₄⁺·C₆H₈BO₆⁻, the trivalent boron is tetrahedrally bonded to four O atoms of the two lactate ions having a chiral carbon in each. Two of the O atoms are covalently bonded [1.4259 (13) Å] to the boron, while there is an extended B—O bonds [1.5177 (14) Å] between the boron and each of the other two O atoms. There are distortions in the tetrahedral angles around boron ranging from 104.47 (5) to 115.35 (15)°. The structure is stabilized by a network of N—H...O hydrogen bonds involving the H atoms of the ammonium cation and the O atoms of the borodilactate anion. The UV–vis transmittance window of this non-linear optical crystal is in the range 240–1250 nm.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.026
• wR factor = 0.103
• Data-to-parameter ratio = 9.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           69.72
         From the CIF: _reflns_number_total                871
         Count of symmetry unique reflns          538
         Completeness (_total/calc)            161.90%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured       333
         Fraction of Friedel pairs measured     0.619
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.

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S1. Comment

The structure determination of the title compound, (I), was undertaken to investigate the environment around boron and the hydrogen bonds involving the ammonium cation. Non-linear Optical (NLO) materials play a vital role in the advancing laser technology and optoelectronic applications, such as optical computing, optical data storage and optical communication. Since it is reported that semiorganic NLO materials combine the large non-linearity of organics and favourable crystal growth properties of inorganic salts (Jiang & Fang, 1999; Jiang et al., 2001), we have prepared the title compound, which crystallizes in the noncentrosymmetric space group C222₁ with Z = 4.

The asymmetric unit of (I) contains half a borodilactate anion and half an ammonium cation. The other halves are generated by twofold symmetry, with B1 and N4 lying on the twofold axes. Atom B1 forms two covalent bonds [1.4259 (13) Å each] with O2 and O2ⁱ and an extended coordination bond [1.5177 (14) Å] resonating between O1 and O1ⁱ [symmetry code: (i) -x, y, 1/2 - z]. The bond angles around boron, O1ⁱ–B1–O2ⁱ [104.47 (5)°], O1–B1–O1ⁱ [105.69 (13)°], O1–B1–O2ⁱ [113.33 (6)°] and O2–B1–O2ⁱ [115.35 (15)°] indicate a distorted tetrahedral environment. Similar bond lengths and deviations from the tetrahedral values of bond angles around boron have been reported in the literature (Stibrany & Brant, 2001; Hill et al., 1997). The dihedral angle between the planes of the two lactate moieties of the boro dilactate anion is 88.3°.

The structure is stabilized by a network of N—H···O hydrogen bonds involving the H atoms of the ammonium cation and two of the O atoms (O2 and O3) of the lactate moiety (Table 2). Because of the space group symmetry all the four H atoms of the ammonium ion are involved in hydrogen bonding with O3 and symmetry-related O2(-x + 1/2, -y + 1/2, z - 1/2), O2(-x + 1/2, y - 1/2, -z + 1/2) and O3(x, -y, -z).

S2. Experimental

The title compound was prepared by mixing 3.93 g (0.025 M) of ammonium carbonate, 3.09 g (0.05 M) of boric acid and 9.08 g (0.1 M) of lactic acid. The components were thoroughly dissolved in 100 ml of distilled water and the mixture was evaporated to dryness by heating at 323 K for 8 h. The yield was around 50%. Single crystals were obtained by slow evaporation of the saturated aqueous solution at 293 K. Good quality single crystals of size 8 × 6 × 3 mm were obtained in a period of two months. The melting point was measured as 489–492 K. The molecular mass was obtained as 205 amu using a Finnigan Mat-8230 GC mass spectrometer. The UV–vis spectrum of the crystal recorded using a Varian Cary 5E UV-vis-NIR spectrophotometer shows a transmittance window in the range 240–1250 nm. The extended UV transparency down to 240 nm makes this crystal preferred for optoelectronic applications.

S3. Refinement

All H atoms were located from a difference map and were included in the structure-factor calculations with U_iso(H) equal to 1.1 U_eq of their respective carrier atom and their parameters were refined. There are two chiral carbons [C5 and C5ⁱ; symmetry code: (i) -x, y, 1/2 - z] in the lactate moieties. The number of Friedel pairs measured was 117 reflections. The absolute configuration of the lactate anion could not be established in the present study, because the structure contains only light atoms. However, the reported coordinates correspond to S configuration.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ZORTEP (Zsolnai, 1997); software used to prepare material for publication: SHELXL97, PARST (Nardelli, 1983) and PLATON (Spek, 2001).

Figures

	Fig. 1. The molecular structure of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme. [Symmetry code: (i) -x, y, 1/2 - z.]
	Fig. 2. The molecular packing viewed down the c axis.

Ammonium 2,7-dimethyl-5-bora-1,4,6,9-tetroxaspiro[4.4]nonane-3,8-dionate

Crystal data

C6H12BNO6	Dx = 1.428 Mg m^−3 Dm = 1.41 Mg m^−3 Dm measured by floatation method
Mr = 204.98	Cu Kα radiation, λ = 1.54180 Å
Orthorhombic, C2221	Cell parameters from 25 reflections
a = 9.3254 (11) Å	θ = 20–30°
b = 11.9482 (15) Å	µ = 1.09 mm^−1
c = 8.5578 (9) Å	T = 293 K
V = 953.53 (19) Å^3	Prismatic, white
Z = 4	0.15 × 0.12 × 0.09 mm
F(000) = 432

Data collection

Enraf-Nonius CAD-4 diffractometer	870 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.021
Graphite monochromator	θmax = 69.7°, θmin = 6.0°
ω–2θ scans	h = −8→11
Absorption correction: ψ scan (North et al., 1968)	k = −8→14
Tmin = 0.854, Tmax = 0.909	l = 0→10
988 measured reflections	2 standard reflections every 120 min
871 independent reflections	intensity decay: neglegible

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.026	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.103	(Δ/σ)max = 0.002
S = 1.05	Δρmax = 0.17 e Å^−3
871 reflections	Δρmin = −0.12 e Å^−3
90 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
2 restraints	Extinction coefficient: 0.027 (3)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983)
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.06 (19)

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 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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.12303 (10)	0.12891 (7)	0.20519 (10)	0.0389 (4)
O2	0.05400 (11)	0.26944 (8)	0.37791 (13)	0.0450 (4)
O3	0.33242 (12)	0.08013 (9)	0.30905 (11)	0.0505 (4)
N4	0.4313 (2)	0.0000	0.0000	0.0479 (5)
C5	0.17701 (14)	0.21563 (10)	0.44043 (14)	0.0388 (4)
C6	0.22229 (14)	0.13421 (10)	0.31305 (15)	0.0374 (4)
C7	0.1444 (2)	0.15577 (16)	0.59146 (15)	0.0530 (4)
B1	0.0000	0.20563 (15)	0.2500	0.0367 (5)
H5	0.254 (4)	0.2726 (18)	0.458 (2)	0.067 (6)*
H71	0.076 (3)	0.099 (2)	0.580 (2)	0.058 (5)*
H72	0.217 (3)	0.1226 (16)	0.629 (2)	0.052 (5)*
H73	0.102 (3)	0.208 (2)	0.664 (3)	0.071 (6)*
H41	0.381 (3)	0.021 (2)	0.081 (2)	0.077 (7)*
H42	0.469 (5)	0.061 (2)	−0.044 (4)	0.133 (15)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0441 (6)	0.0397 (5)	0.0330 (5)	0.0043 (4)	−0.0004 (3)	−0.0042 (3)
O2	0.0441 (5)	0.0398 (6)	0.0511 (6)	0.0081 (4)	−0.0081 (4)	−0.0134 (4)
O3	0.0433 (6)	0.0591 (7)	0.0492 (6)	0.0138 (4)	0.0044 (4)	0.0015 (5)
N4	0.0471 (10)	0.0477 (10)	0.0488 (9)	0.000	0.000	−0.0115 (7)
C5	0.0381 (6)	0.0399 (6)	0.0383 (7)	0.0005 (5)	−0.0029 (5)	−0.0052 (5)
C6	0.0399 (6)	0.0377 (6)	0.0345 (6)	0.0005 (4)	0.0041 (5)	0.0000 (5)
C7	0.0610 (9)	0.0620 (10)	0.0359 (7)	0.0027 (8)	0.0039 (6)	−0.0018 (6)
B1	0.0396 (9)	0.0328 (9)	0.0379 (9)	0.000	−0.0013 (8)	0.000

Geometric parameters (Å, º)

O1—C6	1.3088 (16)	C5—C6	1.5209 (17)
O1—B1	1.5177 (14)	C5—H5	1.00 (3)
O2—C5	1.4197 (16)	C7—H71	0.94 (3)
O2—B1	1.4259 (13)	C7—H72	0.84 (3)
O3—C6	1.2138 (18)	C7—H73	0.96 (3)
N4—H41	0.874 (17)	B1—O2^i	1.4259 (13)
N4—H42	0.896 (19)	B1—O1^i	1.5177 (14)
C5—C7	1.5080 (19)
C6—O1—B1	109.10 (8)	C5—C7—H71	112.9 (13)
C5—O2—B1	109.42 (9)	C5—C7—H72	112.8 (15)
H41—N4—H42	108 (3)	H71—C7—H72	104 (2)
O2—C5—C7	112.02 (13)	C5—C7—H73	109.2 (18)
O2—C5—C6	104.12 (10)	H71—C7—H73	105 (2)
C7—C5—C6	111.53 (11)	H72—C7—H73	113 (2)
O2—C5—H5	109.4 (15)	O2—B1—O2^i	115.35 (15)
C7—C5—H5	109.6 (12)	O2—B1—O1^i	113.33 (6)
C6—C5—H5	110.1 (14)	O2^i—B1—O1^i	104.47 (5)
O3—C6—O1	123.56 (12)	O2—B1—O1	104.47 (5)
O3—C6—C5	126.56 (11)	O2^i—B1—O1	113.33 (6)
O1—C6—C5	109.88 (11)	O1^i—B1—O1	105.69 (13)
B1—O2—C5—C7	−103.80 (12)	C7—C5—C6—O1	111.04 (14)
B1—O2—C5—C6	16.85 (13)	C5—O2—B1—O2^i	−142.32 (11)
B1—O1—C6—O3	178.85 (12)	C5—O2—B1—O1^i	97.32 (12)
B1—O1—C6—C5	−0.52 (13)	C5—O2—B1—O1	−17.23 (13)
O2—C5—C6—O3	170.72 (13)	C6—O1—B1—O2	10.75 (13)
C7—C5—C6—O3	−68.30 (19)	C6—O1—B1—O2^i	137.12 (11)
O2—C5—C6—O1	−9.94 (13)	C6—O1—B1—O1^i	−109.07 (9)

Symmetry code: (i) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H41···O3	0.87 (2)	2.12 (2)	2.9600 (12)	160 (2)
N4—H42···O2^ii	0.89 (3)	2.14 (3)	2.9494 (10)	150 (4)

Symmetry code: (ii) −x+1/2, −y+1/2, z−1/2.