Potassium penta­borate

Wu, Q.

doi:10.1107/S1600536811043807

inorganic compounds

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ISSN: 2056-9890

Volume 67| Part 11| November 2011| Page i67

doi:10.1107/S1600536811043807

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Potassium pentaborate

Qi Wu ^a ^*

^aDepartment of Power Engineering, Xian Aeronautical College, Xian 710077, People's Republic of China
^*Correspondence e-mail: 62010375@163.com

(Received 24 August 2011; accepted 21 October 2011; online 29 October 2011)

The title compound, K[B₅O₇(OH)₂], was obtained from a hydrothermal reaction. The structure is composed of one K⁺ cation and a polyborate ¹_∞[B₅O₇(OH)₂]⁻ anion, which consists of two six-membered rings linked by a common BO₄ tetrahedron. The [B₅O₇(OH)₂]⁻ units are linked together through two exocyclic O atoms to neighbouring units, forming a helical chain structure extending parallel to [010]. Adjacent chains are further connected into a three-dimensional structure by K—O bonds and weak O—H⋯O hydrogen-bond interactions.

Related literature

For the nonlinear optical properties of alkali metal borates, see: Mori et al. (1995 ). For syntheses and crystal structures in the K₂O–B₂O₃–H₂O system, see: Marezio (1969 ); Salentine (1987 ); Wang et al. (2006 ); Zhang et al. (2005 ).

Experimental

Crystal data

K[B₅O₇(OH)₂]
M_r = 239.17
Monoclinic, P 2₁ /c
a = 7.6690 (3) Å
b = 9.0445 (3) Å
c = 12.2304 (4) Å
β = 119.132 (2)°
V = 741.01 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.74 mm⁻¹
T = 100 K
0.14 × 0.09 × 0.07 mm

Data collection

Bruker APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a ) T_min = 0.878, T_max = 0.910
13002 measured reflections
1452 independent reflections
1343 reflections with I > 2σ(I)
R_int = 0.027

Refinement

R[F² > 2σ(F²)] = 0.030
wR(F²) = 0.072
S = 1.00
1452 reflections
136 parameters
H-atom parameters constrained
Δρ_max = 0.77 e Å⁻³
Δρ_min = −0.87 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O10—H10A⋯O6ⁱ	0.84	2.36	3.179 (2)	164
O12—H12A⋯O11ⁱⁱ	0.84	2.30	3.0346 (19)	147
O12—H12A⋯O4ⁱⁱ	0.84	2.50	3.170 (2)	138
Symmetry codes: (i) $[x-1, -y-{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (ii) -x, -y, -z.

Data collection: APEX2 (Bruker, 2009 ); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: SHELXTL (Sheldrick, 2008b); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811043807/fi2113sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811043807/fi2113Isup2.hkl

checkCIF report

Comment top

Boron can form a large variety of compounds due to the variability of the coordination environment about B. In the past several decades, much interest has focused on studies of alkali metals borates because some of these compounds show interesting physical properties, such as nonlinear optical behavior for CsLiB₆O₁₀ (Mori et al., 1995). So far, several phases had been obtained in the K₂O–B₂O₃–H₂O system (Marezio, 1969; Salentine, 1987; Zhang et al., 2005; Wang et al., 2006). In this paper, we describe the synthesis and the crystal structure of a new potassium borate, K[B₅O₇(OH)₂].

It features one K⁺ cation and a ¹_∞[B₅O₇(OH)₂]^- polyborate anion (Fig.1), which is closely related to the reported compound of K[B₅O₇(OH)₂]^.H₂O (Zhang et al., 2005).

The ¹_∞[B₅O₇(OH)₂]^- ion consists of two six-membered rings linked by a common B atom. Each six-membered ring consists of one BO₃ triangle, one BO₂(OH) triangle and a common BO₄ tetrahedron. The [B₅O₇(OH)₂]^- units are linked via two exocyclic O atoms (O8 and O8A) to neighboring units, forming a 1-D helical chainlike structure (Fig. 2). Adjacent chains are further connected into a 3-D structure by K—O bonds and O—H···O hydrogen bonds interactions, as shown in Fig.3.

Related literature top

For the nonlinear optical properties of alkali metal borates, see: Mori et al. (1995). For syntheses and crystal structures in the K₂O–B₂O₃–H₂O system, see: Marezio (1969); Salentine (1987); Wang et al. (2006); Zhang et al. (2005).

Experimental top

All reagents used in the synthesis were analytic grade and were used without further purification. A mixture of GaO(OH) (0.06 g), H₃BO₃(0.47 g), KNO₃ (0.15 g) and distilled water (0.1 ml) was sealed in a Teflon-lined bomb and heated at 483 K for 3 d and then cooled to room temperature. The resulting colorless crystals were washed with hot deionized water and dried in a vacuum dryer to a constant mass at room temperature.

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: SHELXTL (Sheldrick, 2008b); software used to prepare material for publication: SHELXTL (Sheldrick, 2008b).

Figures top

	Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) -x, -1/2 + y, -1/2 - z.
	Fig. 2. The one-dimensional chain structure constructed by [B₅O₇(OH)₂]^- units. B, O and H atoms are shown as green, red and yellow, respectively.
	Fig. 3. Packing view along the c axis of title compound, showing three-dimensional structure constructed by O—H···O hydrogen bonds, where all potassium cations are omitted for clarity. B, O and H atoms are shown as green, red and yellow, respectively. H bonds are drawn as dashed lines.

Potassium pentaborate top

Crystal data top

K[B₅O₇(OH)₂]	F(000) = 472
M_r = 239.17	D_x = 2.144 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 6851 reflections
a = 7.6690 (3) Å	θ = 3.0–30.5°
b = 9.0445 (3) Å	µ = 0.74 mm⁻¹
c = 12.2304 (4) Å	T = 100 K
β = 119.132 (2)°	Rod, colourless
V = 741.01 (5) Å³	0.14 × 0.09 × 0.07 mm
Z = 4

Data collection top

Bruker APEXII diffractometer	1452 independent reflections
Radiation source: fine-focus sealed tube	1343 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.027
Detector resolution: 83.33 pixels mm^-1	θ_max = 26.0°, θ_min = 3.0°
ϕ and ω scans	h = −9→8
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a)	k = −11→11
T_min = 0.878, T_max = 0.910	l = −15→15
13002 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.072	H-atom parameters constrained
S = 1.00	w = 1/[σ²(F_o²) + (0.026P)² + 1.7263P] where P = (F_o² + 2F_c²)/3
1452 reflections	(Δ/σ)_max < 0.001
136 parameters	Δρ_max = 0.77 e Å⁻³
0 restraints	Δρ_min = −0.87 e Å⁻³

Crystal data top

K[B₅O₇(OH)₂]	V = 741.01 (5) Å³
M_r = 239.17	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 7.6690 (3) Å	µ = 0.74 mm⁻¹
b = 9.0445 (3) Å	T = 100 K
c = 12.2304 (4) Å	0.14 × 0.09 × 0.07 mm
β = 119.132 (2)°

Data collection top

Bruker APEXII diffractometer	1452 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a)	1343 reflections with I > 2σ(I)
T_min = 0.878, T_max = 0.910	R_int = 0.027
13002 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.030	0 restraints
wR(F²) = 0.072	H-atom parameters constrained
S = 1.00	Δρ_max = 0.77 e Å⁻³
1452 reflections	Δρ_min = −0.87 e Å⁻³
136 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
O4	−0.2494 (2)	−0.13046 (15)	−0.14778 (13)	0.0093 (3)
O5	−0.0757 (2)	−0.32468 (15)	−0.19460 (13)	0.0095 (3)
O6	0.0327 (2)	−0.25360 (15)	0.01760 (12)	0.0096 (3)
O7	−0.4011 (2)	−0.14669 (15)	−0.50951 (12)	0.0097 (3)
O8	0.1858 (2)	−0.45303 (15)	−0.01975 (13)	0.0091 (3)
O9	−0.4141 (2)	−0.26660 (15)	−0.33902 (12)	0.0095 (3)
O10	−0.6325 (2)	−0.33377 (16)	−0.55281 (13)	0.0111 (3)
H10A	−0.7360	−0.3223	−0.5465	0.017*
O11	−0.1489 (2)	−0.08947 (15)	−0.30142 (13)	0.0101 (3)
O12	−0.1416 (2)	−0.06260 (16)	0.05911 (13)	0.0108 (3)
H12A	−0.0286	−0.0380	0.1172	0.016*
B1	0.0458 (3)	−0.3419 (2)	−0.0712 (2)	0.0088 (4)
B2	−0.1192 (3)	−0.1489 (2)	−0.0252 (2)	0.0094 (4)
B3	−0.4815 (3)	−0.2516 (2)	−0.4635 (2)	0.0095 (4)
B4	−0.2217 (3)	−0.2019 (2)	−0.2457 (2)	0.0093 (4)
B5	0.2421 (3)	−0.5629 (2)	−0.0753 (2)	0.0091 (4)
K1	0.34799 (7)	−0.07665 (5)	−0.26481 (4)	0.01448 (14)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O4	0.0097 (7)	0.0089 (7)	0.0088 (7)	0.0014 (5)	0.0040 (6)	0.0006 (5)
O5	0.0104 (7)	0.0097 (7)	0.0085 (7)	0.0015 (5)	0.0047 (6)	0.0002 (5)
O6	0.0104 (7)	0.0098 (7)	0.0080 (7)	0.0016 (5)	0.0041 (6)	−0.0002 (5)
O7	0.0109 (7)	0.0097 (7)	0.0080 (6)	−0.0017 (6)	0.0040 (6)	−0.0001 (5)
O8	0.0102 (7)	0.0092 (7)	0.0077 (6)	0.0014 (5)	0.0043 (6)	0.0001 (5)
O9	0.0093 (7)	0.0100 (7)	0.0089 (7)	−0.0010 (5)	0.0041 (6)	0.0008 (5)
O10	0.0096 (7)	0.0126 (7)	0.0112 (7)	−0.0027 (6)	0.0051 (6)	−0.0009 (6)
O11	0.0092 (7)	0.0112 (7)	0.0085 (7)	−0.0021 (5)	0.0032 (6)	0.0009 (5)
O12	0.0098 (7)	0.0115 (7)	0.0095 (7)	0.0018 (5)	0.0035 (6)	−0.0015 (5)
B1	0.0095 (10)	0.0070 (10)	0.0105 (10)	−0.0015 (8)	0.0052 (9)	−0.0004 (8)
B2	0.0101 (10)	0.0073 (10)	0.0124 (11)	−0.0014 (8)	0.0067 (9)	0.0003 (8)
B3	0.0097 (10)	0.0074 (10)	0.0118 (11)	0.0016 (8)	0.0054 (9)	−0.0003 (8)
B4	0.0098 (10)	0.0083 (10)	0.0092 (10)	0.0000 (8)	0.0043 (9)	0.0005 (8)
B5	0.0100 (10)	0.0082 (10)	0.0111 (10)	−0.0005 (8)	0.0067 (9)	0.0000 (8)
K1	0.0143 (2)	0.0188 (3)	0.0091 (2)	0.00475 (18)	0.00474 (18)	0.00124 (17)

Geometric parameters (Å, º) top

O4—B2	1.347 (3)	O9—B3	1.356 (3)
O4—B4	1.464 (3)	O9—B4	1.477 (3)
O5—B1	1.342 (3)	O10—B3	1.362 (3)
O5—B4	1.482 (3)	O10—H10A	0.8400
O6—B1	1.391 (3)	O11—B5ⁱ	1.339 (3)
O6—B2	1.391 (3)	O11—B4	1.477 (3)
O7—B5ⁱ	1.381 (3)	O12—B2	1.369 (3)
O7—B3	1.391 (3)	O12—H12A	0.8400
O8—B1	1.379 (3)	B5—O11ⁱⁱ	1.339 (3)
O8—B5	1.386 (3)	B5—O7ⁱⁱ	1.381 (3)

B2—O4—B4	122.10 (16)	O12—B2—O6	119.56 (18)
B1—O5—B4	121.96 (16)	O9—B3—O10	123.79 (19)
B1—O6—B2	117.54 (16)	O9—B3—O7	121.38 (18)
B5ⁱ—O7—B3	118.31 (16)	O10—B3—O7	114.82 (17)
B1—O8—B5	131.13 (17)	O4—B4—O11	108.14 (16)
B3—O9—B4	121.29 (16)	O4—B4—O9	108.59 (16)
B3—O10—H10A	109.4	O11—B4—O9	112.07 (16)
B5ⁱ—O11—B4	121.94 (16)	O4—B4—O5	111.51 (16)
B2—O12—H12A	109.4	O11—B4—O5	109.41 (16)
O5—B1—O8	123.92 (19)	O9—B4—O5	107.14 (16)
O5—B1—O6	122.50 (18)	O11ⁱⁱ—B5—O7ⁱⁱ	122.64 (18)
O8—B1—O6	113.46 (17)	O11ⁱⁱ—B5—O8	123.92 (19)
O4—B2—O12	118.11 (18)	O7ⁱⁱ—B5—O8	113.41 (18)
O4—B2—O6	122.32 (18)

B4—O5—B1—O8	−178.99 (18)	B2—O4—B4—O11	−103.7 (2)
B4—O5—B1—O6	5.3 (3)	B2—O4—B4—O9	134.42 (18)
B5—O8—B1—O5	3.4 (3)	B2—O4—B4—O5	16.6 (3)
B5—O8—B1—O6	179.45 (18)	B5ⁱ—O11—B4—O4	−125.34 (19)
B2—O6—B1—O5	3.0 (3)	B5ⁱ—O11—B4—O9	−5.7 (3)
B2—O6—B1—O8	−173.13 (17)	B5ⁱ—O11—B4—O5	113.01 (19)
B4—O4—B2—O12	171.24 (17)	B3—O9—B4—O4	135.83 (18)
B4—O4—B2—O6	−10.0 (3)	B3—O9—B4—O11	16.4 (3)
B1—O6—B2—O4	−0.7 (3)	B3—O9—B4—O5	−103.6 (2)
B1—O6—B2—O12	178.03 (17)	B1—O5—B4—O4	−14.3 (3)
B4—O9—B3—O10	165.13 (18)	B1—O5—B4—O11	105.3 (2)
B4—O9—B3—O7	−16.1 (3)	B1—O5—B4—O9	−132.97 (18)
B5ⁱ—O7—B3—O9	3.6 (3)	B1—O8—B5—O11ⁱⁱ	−6.9 (3)
B5ⁱ—O7—B3—O10	−177.49 (17)	B1—O8—B5—O7ⁱⁱ	175.04 (18)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O10—H10A···O6ⁱⁱⁱ	0.84	2.36	3.179 (2)	164
O12—H12A···O11^iv	0.84	2.30	3.0346 (19)	147
O12—H12A···O4^iv	0.84	2.50	3.170 (2)	138

Symmetry codes: (iii) x−1, −y−1/2, z−1/2; (iv) −x, −y, −z.

Experimental details

Crystal data
Chemical formula	K[B₅O₇(OH)₂]
M_r	239.17
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	7.6690 (3), 9.0445 (3), 12.2304 (4)
β (°)	119.132 (2)
V (Å³)	741.01 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.74
Crystal size (mm)	0.14 × 0.09 × 0.07

Data collection
Diffractometer	Bruker APEXII diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2008a)
T_min, T_max	0.878, 0.910
No. of measured, independent and observed [I > 2σ(I)] reflections	13002, 1452, 1343
R_int	0.027
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.072, 1.00
No. of reflections	1452
No. of parameters	136
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.77, −0.87

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008b), SHELXL97 (Sheldrick, 2008b), SHELXTL (Sheldrick, 2008b).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O10—H10A···O6ⁱ	0.84	2.36	3.179 (2)	164
O12—H12A···O11ⁱⁱ	0.84	2.30	3.0346 (19)	147
O12—H12A···O4ⁱⁱ	0.84	2.50	3.170 (2)	138

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

Acknowledgements

The author thanks the National Natural Science Foundation of China (grant No. 20871078) for supporting this study.

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