Refinement of lithium tetra­hydroxo­borate with low-temperature CCD data

Refinement of the title compound, Li B(OH)₄, with CCD data at 120 K has led to a sevenfold increase in precision over the previously reported structure based on film data. The H atoms have been located and refined. Both Li and B are tetrahedrally coordinated. B-O distances are in the range 1.4644 (14)-1.4989 (13) Å, while Li-O distances are in the range 1.931 (2)-2.022 (2) Å.

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](O-B) = 0.001 Å
• R factor = 0.029
• wR factor = 0.069
• Data-to-parameter ratio = 12.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

While attempting to prepare RhH₂(et,ph-P4) from RhCl₂(et,ph-P4) (where et,ph-P4 is (Et₂PCH₂CH₂)(Ph)PCH₂P(Ph)CH₂CH₂PEt₂) using `super hydride' LiBH(C₂H₅)₃, we encountered crystals of the title compound as a byproduct, and determined its structure to ascertain its identity. The room-temperature structure was previously reported, based on intensities from Weissenberg films, by Höhne (1964, 1966) and coworkers (Kutschabsky & Höhne, 1965; Kutschabsky & Reck, 1966). Our results confirm the published structure, with an approximate sevenfold increase in precision. Höhne's assigned H-atom positions, assigned from difference maps, lie 0.17–0.38 Å from our refined H-atom positions. Höhne's range of B—O distances, 1.472 (8) to 1.498 (8) Å, and range of Li—O distances, 1.929 (16) to 2.015 (16) Å, are in good agreement with our results (see Abstract). Although all four hydrogen bonds are nearly linear, some short intermolecular contacts exist between H atoms of hydrogen-bonded OH groups. The shortest of these is 2.06 (2) Å [H1···H3(x - 1/2, y, 3/2 - z)]. Short intramolecular O–H···O interactions also exist within the B(OH)₄^- ion. All four OH hydrogen atoms are approximately eclipsed (B–O–H···O torsion angles <30°) with an adjacent OH, and O···H distances are in the range 2.23 (2)–2.51 (2) Å. The O–H···O angles in these contacts are in the range 73 (2)–85 (2)°.

S2. Experimental

A 1.0 M solution of LiBH(C₂H₅)₃ in tetrahydrofuran (0.8 ml, 0.8 mmol) was added dropwise to a rapidly stirring 1 ml me thanol solution containing RhCl₂ (et,ph-P4) (0.5 g, 0.784 mmol) and allowed to react for 24 h. A 1 ml sample of this dark-red solution was allowed to remain undisturbed in an NMR tube for approximately 30 days, which allowed slow solvent evaporation and the formation of colorless crystals of lithium tetrahydroxoborate.

S3. Refinement

H atoms were located from difference maps, and were individually refined. O—H distances were in the range 0.793 (18)–0.845 (18) Å, and U_iso values for H atoms are in the range 0.027 (4)–0.038 (5) Ų.

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: HKL SCALEPACK (Otwinowski & Minor 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: Direct_methods (SIR97; Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. View of the title compound showing numbering scheme with ellipsoids drawn at the 50% level.

Lithium tetrahydroxoborate

Crystal data

Li^+·BO4H4^−	Dx = 1.836 Mg m^−3
Mr = 85.78	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 1047 reflections
a = 7.9362 (3) Å	θ = 2.5–30.0°
b = 8.5220 (3) Å	µ = 0.18 mm^−1
c = 9.1762 (4) Å	T = 120 K
V = 620.61 (4) Å^3	Octahedron, colorless
Z = 8	0.20 × 0.18 × 0.17 mm
F(000) = 352

Data collection

KappaCCD (with Oxford Cryostream) diffractometer	787 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.021
Graphite monochromator	θmax = 30.0°, θmin = 2.5°
ω scans with κ offsets	h = −11→11
6073 measured reflections	k = −11→12
907 independent reflections	l = −12→12

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)] = 0.029	Hydrogen site location: difference Fourier map
wR(F^2) = 0.069	All H-atom parameters refined
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0204P)^2 + 0.3132P] where P = (Fo^2 + 2Fc^2)/3
907 reflections	(Δ/σ)max < 0.001
71 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.30 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 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
Li1	0.1319 (2)	0.3741 (2)	0.3016 (2)	0.0127 (4)
B1	0.32892 (15)	0.33617 (13)	0.59296 (13)	0.0089 (2)
O1	0.16392 (10)	0.29123 (9)	0.65473 (9)	0.00989 (18)
O2	0.29301 (10)	0.41668 (9)	0.45417 (8)	0.01158 (19)
O3	0.42395 (10)	0.44191 (8)	0.68819 (8)	0.00999 (18)
O4	0.43403 (10)	0.19150 (9)	0.57379 (9)	0.01098 (18)
H1	0.097 (2)	0.2814 (19)	0.5891 (19)	0.028 (4)*
H2	0.381 (2)	0.455 (2)	0.418 (2)	0.038 (5)*
H3	0.492 (2)	0.3964 (18)	0.735 (2)	0.027 (4)*
H4	0.373 (2)	0.117 (2)	0.5432 (18)	0.027 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Li1	0.0142 (9)	0.0133 (9)	0.0105 (8)	−0.0010 (7)	−0.0006 (7)	−0.0005 (7)
B1	0.0090 (5)	0.0092 (5)	0.0084 (5)	−0.0002 (4)	0.0003 (4)	0.0005 (4)
O1	0.0083 (4)	0.0121 (4)	0.0093 (4)	−0.0004 (3)	0.0004 (3)	0.0009 (3)
O2	0.0102 (4)	0.0148 (4)	0.0098 (4)	−0.0032 (3)	−0.0011 (3)	0.0030 (3)
O3	0.0109 (4)	0.0092 (4)	0.0099 (4)	0.0008 (3)	−0.0032 (3)	−0.0001 (3)
O4	0.0094 (4)	0.0101 (4)	0.0135 (4)	0.0005 (3)	−0.0007 (3)	−0.0019 (3)

Geometric parameters (Å, º)

Li1—O1^i	1.966 (2)	B1—O3	1.4644 (14)
Li1—O2	1.931 (2)	B1—O4	1.4989 (13)
Li1—O3^ii	1.933 (2)	O1—H1	0.807 (18)
Li1—O4^iii	2.022 (2)	O2—H2	0.837 (19)
B1—O1	1.4774 (13)	O3—H3	0.793 (18)
B1—O2	1.4745 (14)	O4—H4	0.845 (18)
O2—Li1—O3^ii	112.95 (10)	B1—O1—Li1^iv	124.28 (8)
O2—Li1—O1^i	123.10 (10)	B1—O1—H1	108.8 (12)
O3^ii—Li1—O1^i	104.01 (9)	Li1^iv—O1—H1	110.6 (12)
O2—Li1—O4^iii	98.98 (9)	B1—O2—Li1	131.84 (9)
O3^ii—Li1—O4^iii	110.53 (10)	B1—O2—H2	111.3 (13)
O1^i—Li1—O4^iii	106.85 (9)	Li1—O2—H2	109.6 (13)
O3—B1—O2	109.18 (8)	B1—O3—Li1^v	134.60 (9)
O3—B1—O1	112.77 (9)	B1—O3—H3	112.1 (12)
O2—B1—O1	106.30 (8)	Li1^v—O3—H3	104.9 (12)
O3—B1—O4	106.83 (8)	B1—O4—Li1^vi	126.40 (8)
O2—B1—O4	112.89 (9)	B1—O4—H4	109.9 (11)
O1—B1—O4	108.97 (8)	Li1^vi—O4—H4	115.0 (11)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^iii	0.807 (18)	1.990 (18)	2.7835 (11)	167.4 (16)
O2—H2···O3^vii	0.837 (19)	2.03 (2)	2.8643 (11)	173.4 (18)
O3—H3···O1^viii	0.793 (18)	1.919 (19)	2.7117 (11)	177.4 (18)
O4—H4···O2^ix	0.845 (18)	2.308 (18)	3.1522 (11)	178.6 (16)

Symmetry codes: (iii) x−1/2, −y+1/2, −z+1; (vii) −x+1, −y+1, −z+1; (viii) x+1/2, y, −z+3/2; (ix) −x+1/2, y−1/2, z.