A new hydrated ammonium hydroxy­borate, (NH₄)₂[B₁₀O₁₄(OH)₄]·H₂O

The structure of a new synthetic compound, di­ammonium tetra­hydroxy­deca­borate monohydrate, has been determined by single-crystal X-ray diffraction. It crystallizes in triclinic space group and all atoms occupy general sites. The title compound is composed of [B₁₀O₁₅(OH)₄]^4- ions as the fundamental building blocks, and these are linked end-to-end by sharing two common O atoms, thus producing infinite chains of composition [B₁₀O₁₄(OH)₄]_n^2n-. These chains are linked by hydrogen bonds, thus forming borate sheets. Water mol­ecules and ammonium ions between these sheets connect adjacent sheets via hydrogen bonds.

S1. Comment

Borates are conventionally obtained by high-temperature solid-state or hydrothermal reactions. In order to enrich the borate chemistry and explore more practical materials, an unusual synthetic method involving a flux of molten boric acid was proposed for the synthesis of new borates (Williams et al., 1998; Li et al., 2002). The present work is part of a series of studies aimed at synthesizing new borates from boric acid flux. Several natural or synthetic ammonium borates, e.g. larderellite [NH₄B₅O₇(OH)₂·H₂O; Merlino et al.,1969] and ammonioborite [(NH₄₎3B₁₅O₂₀(OH)₈·4H₂O; Merlino et al.,1971], have been found previously, but the title compound, (I), obtained from a boric acid flux, differs from all known ammonium borates. The experimental powder pattern, IR spectrum and ICP analysis of (I) are in good agreement with the results of single-crystal X-ray diffraction analysis.

The basic structural unit in (I) is a double ring consisting of one BO₄ tetrahedron and four BO₃ triangles. This unit was first found in K[B₅O₆(OH)₄]·2H₂O as an isolated ion (Zachariasen, 1937). In larderellite, these structural units are linked to form infinite chains, while in ammonioborite, three of these structural units are connected to give trimeric ions with C₂-2 symmetry. However, in (I), two of the basic structural units with no symmetric relation are connected to a dimeric ion. Inclusive of H atoms bonded to the terminal O atoms, the dimeric ion is [B₁₀O₁₅(OH)₄]⁴⁻, which is the fundamental building block (FBB) of (I) (Fig. 1). After making a careful inspection of known borates, we believe that (I) is a new borate FBB.

The FBBs in (I) are linked end-to-end by sharing two O atoms, thus forming infinite chains along the b axis with the composition [B₁₀O₁₄(OH)₄]_n^2n-. Two symmetry-equivalent chains pass through the unit cell. These parallel chains are aligned along the a axis and are linked via hydrogen bonds, thus forming infinite sheets approximately parallel to the ab plane (Fig. 2). Ammonium ions and water molecules are located between these sheets, which are connected to one another via hydrogen bonds. The O atoms of the water molecules are disordered, presumably as a result of the large space between the sheets.

The general structural features and the composition are very similar in (I) and in larderellite, but the layout of their borate chains are different. In the title compound, two parallel chains run through a unit cell, but in larderellite, the two chains running through the unit cell intersect. Furthermore, in the chains of larderellite, each [B₅O₁₀] unit is obtained from the preceding one through the operation of a screw diad axis (Merlino et al., 1969), but in the title compound, adjacent [B₅O₁₀] units in each chain are symmetry distinct.

In the title compound, the triangular BO₃ groups are slightly distorted, with an average B—O bond length of 1.366 Å and B—O—B angles in the range 113.72–124.50°. The BO₄ groups are almost perfect tetrahedra, with a mean B—O distance of 1.469 Å and B—O—B angles in the range 107.65–111.85° (Table 1). These average bond lengths are in agreement with the data reviewed by Hawthorne et al. (1996).

The hydrogen bonds within the sheets originate from the H atoms of hydroxy groups and the O atoms in the sheets, and the hydorgen bonds between the sheets are attributed to the H atoms of the ammonium ions, water molecules and the O atoms in the sheets (Table 2). Each ammonium ion is hydrogen bonded to the two adjacent sheets, but each water molecule is only hydrogen bonded to one neighboring sheet.

S2. Experimental

The title compound was synthesized using boric acid as a flux. All reagents were of analytical grade. A mixture of V₂O₅ (0.22 g), H₂O (1 ml) and NH₂CH₂CH₂NH₂ (0.5 ml) was stirred to obtain a transparent solution, which was mixed with H₃BO₃ (3.09 g), charged into a Teflon 50 ml autoclave and heated at 493 K for 7 d. The excess boric acid was removed by washing the products with hot distilled water and colorless crystals suitable for single-crystal diffraction analysis were easily isolated from the mixtures.

S3. Refinement

Difference Fourier analysis indicated residual electron density about 1 Å from positions O19A and O19B. Further refinement revealed that these two positions corresponded to O atoms with occupancies of 0.64 and 0.36, respectively. In addition, the difference Fourier analysis was able to locate H atoms around these O atoms; these atoms form a disordered water molecule with the occupancy ratio of about 2:1. A l l H atoms? were then refined without constraints. During the data collection, we did not observe any indication of superstructure reflections.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: Bruker SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and ViewerLite4.2 (Accelrys, 2001); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The fundamental building block in (NH4)2[B10O14(OH)4]·H2O. Displacement ellipsoids are drawn here at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. The borate sheet in (NH4)2[B10O14(OH)4]·H2O, displayed in stick style.

diammonium tetrahydroxodecaborate monohydrate

Crystal data

(NH4)2[B10O14(OH)4]·H2O	Z = 2
Mr = 454.23	F(000) = 460
Triclinic, P1	Dx = 1.900 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.6207 (15) Å	Cell parameters from 4431 reflections
b = 9.2328 (18) Å	θ = 2.8–33.0°
c = 11.926 (2) Å	µ = 0.18 mm^−1
α = 99.46 (3)°	T = 293 K
β = 105.89 (3)°	Tabular, colourless
γ = 91.54 (3)°	0.4 × 0.2 × 0.1 mm
V = 793.8 (3) Å^3

Data collection

Bruker SMART APEX CCD area-detector diffractometer	4462 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.020
Graphite monochromator	θmax = 33.0°, θmin = 2.8°
Detector resolution: 15X15microns pixels mm^-1	h = −9→11
ω scans	k = −14→12
7470 measured reflections	l = −18→18
5466 independent reflections

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.118	H atoms treated by a mixture of independent and constrained refinement
S = 1.01	w = 1/[σ^2(Fo^2) + (0.077P)^2] where P = (Fo^2 + 2Fc^2)/3
5466 reflections	(Δ/σ)max = 0.006
346 parameters	Δρmax = 0.52 e Å^−3
0 restraints	Δρmin = −0.34 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	Occ. (<1)
O1	0.42499 (11)	0.23343 (9)	0.35569 (6)	0.01815 (16)
O2	0.99188 (11)	0.75950 (8)	0.52156 (6)	0.01740 (15)
O3	0.61866 (11)	0.14699 (8)	0.52089 (6)	0.01749 (16)
O4	0.61493 (11)	0.35254 (9)	0.05077 (7)	0.01859 (16)
O5	0.79488 (11)	0.54033 (9)	0.02143 (6)	0.01906 (16)
O6	1.20771 (11)	0.57620 (9)	0.54853 (7)	0.02014 (17)
O7	0.82928 (11)	0.78708 (9)	0.32590 (6)	0.01856 (16)
O8	0.76414 (11)	0.54187 (9)	0.21453 (7)	0.01964 (17)
O9	0.79506 (10)	−0.05193 (8)	0.49620 (6)	0.01654 (15)
O10	0.59655 (11)	0.24094 (9)	0.21651 (6)	0.01825 (16)
O11	0.62784 (11)	0.04265 (9)	0.32648 (6)	0.01853 (16)
O12	0.34932 (11)	0.05092 (9)	0.17916 (6)	0.01881 (16)
O13	1.05277 (11)	0.60613 (9)	0.35754 (7)	0.01882 (16)
O14	0.40864 (11)	0.15231 (9)	0.02035 (6)	0.01926 (17)
O15	0.44718 (12)	0.34444 (10)	0.55542 (7)	0.02216 (17)
O16	0.98703 (11)	0.71225 (9)	0.18264 (7)	0.01900 (16)
O17	0.97958 (12)	0.73044 (9)	−0.01127 (7)	0.02201 (18)
O18	0.19933 (12)	−0.04998 (10)	−0.02210 (7)	0.02292 (18)
B1	0.72646 (16)	0.47890 (13)	0.10033 (10)	0.0147 (2)
B2	0.54303 (16)	0.24956 (13)	0.10078 (10)	0.0149 (2)
B3	0.50055 (16)	0.14206 (13)	0.26907 (10)	0.0154 (2)
B4	0.91917 (16)	0.66183 (12)	0.06516 (10)	0.0155 (2)
B5	0.31933 (16)	0.05059 (13)	0.06187 (10)	0.0155 (2)
B6	0.67770 (16)	0.04462 (12)	0.44356 (10)	0.0143 (2)
B7	0.90737 (16)	0.66144 (13)	0.26985 (10)	0.0158 (2)
B8	0.49463 (16)	0.24418 (13)	0.47377 (10)	0.0157 (2)
B9	1.08203 (16)	0.64653 (12)	0.47494 (10)	0.0155 (2)
B10	0.86805 (16)	0.82966 (13)	0.44331 (10)	0.0147 (2)
N2	0.98778 (18)	0.04438 (14)	0.25324 (10)	0.0277 (2)
N1	0.4036 (2)	0.72706 (17)	0.21001 (11)	0.0354 (3)
O19A	0.1224 (5)	0.3482 (4)	0.2383 (2)	0.0325 (9)	0.634 (13)
O19B	0.1993 (15)	0.4056 (12)	0.2285 (3)	0.049 (3)	0.366 (13)
H1	0.383 (3)	0.414 (2)	0.5312 (19)	0.054 (6)*
H2	0.144 (3)	−0.112 (2)	0.0000 (16)	0.044 (5)*
H3	0.395 (3)	0.690 (3)	0.134 (2)	0.063 (6)*
H4	1.224 (3)	0.608 (2)	0.6167 (19)	0.050 (6)*
H5	0.439 (5)	0.823 (4)	0.231 (3)	0.122 (12)*
H6	0.924 (4)	0.046 (3)	0.176 (2)	0.077 (8)*
H7	0.967 (4)	−0.035 (4)	0.269 (3)	0.104 (11)*
H8	0.477 (4)	0.676 (4)	0.255 (3)	0.095 (9)*
H9	1.114 (5)	0.050 (3)	0.258 (2)	0.091 (9)*
H10	0.290 (5)	0.744 (4)	0.224 (3)	0.115 (11)*
H11	0.934 (3)	0.683 (2)	−0.0881 (17)	0.046 (5)*
H12	0.989 (5)	0.119 (4)	0.315 (3)	0.137 (13)*
H13	0.246 (4)	0.335 (3)	0.277 (2)	0.072 (7)*
H14	0.113 (3)	0.433 (3)	0.276 (2)	0.063 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0208 (4)	0.0188 (4)	0.0151 (3)	0.0067 (3)	0.0046 (3)	0.0038 (3)
O2	0.0220 (4)	0.0154 (4)	0.0136 (3)	0.0068 (3)	0.0032 (3)	0.0016 (3)
O3	0.0227 (4)	0.0159 (4)	0.0132 (3)	0.0067 (3)	0.0042 (3)	0.0014 (3)
O4	0.0239 (4)	0.0156 (4)	0.0147 (3)	−0.0078 (3)	0.0043 (3)	0.0018 (3)
O5	0.0261 (4)	0.0166 (4)	0.0135 (3)	−0.0075 (3)	0.0059 (3)	0.0006 (3)
O6	0.0243 (4)	0.0188 (4)	0.0159 (4)	0.0077 (3)	0.0030 (3)	0.0029 (3)
O7	0.0238 (4)	0.0173 (4)	0.0128 (3)	0.0063 (3)	0.0028 (3)	0.0010 (3)
O8	0.0238 (4)	0.0194 (4)	0.0142 (3)	−0.0078 (3)	0.0062 (3)	−0.0011 (3)
O9	0.0207 (4)	0.0141 (3)	0.0140 (3)	0.0060 (3)	0.0033 (3)	0.0023 (3)
O10	0.0206 (4)	0.0187 (4)	0.0135 (3)	−0.0053 (3)	0.0021 (3)	0.0032 (3)
O11	0.0247 (4)	0.0185 (4)	0.0134 (3)	0.0083 (3)	0.0060 (3)	0.0038 (3)
O12	0.0218 (4)	0.0191 (4)	0.0141 (3)	−0.0064 (3)	0.0034 (3)	0.0031 (3)
O13	0.0231 (4)	0.0158 (4)	0.0156 (3)	0.0059 (3)	0.0037 (3)	−0.0003 (3)
O14	0.0233 (4)	0.0182 (4)	0.0138 (3)	−0.0086 (3)	0.0022 (3)	0.0027 (3)
O15	0.0300 (4)	0.0199 (4)	0.0177 (4)	0.0114 (3)	0.0081 (3)	0.0024 (3)
O16	0.0225 (4)	0.0175 (4)	0.0154 (3)	−0.0062 (3)	0.0052 (3)	−0.0001 (3)
O17	0.0285 (4)	0.0195 (4)	0.0191 (4)	−0.0066 (3)	0.0096 (3)	0.0031 (3)
O18	0.0268 (4)	0.0222 (4)	0.0165 (3)	−0.0120 (3)	0.0019 (3)	0.0034 (3)
B1	0.0160 (5)	0.0136 (5)	0.0140 (5)	−0.0013 (4)	0.0039 (4)	0.0026 (4)
B2	0.0168 (5)	0.0125 (5)	0.0146 (5)	−0.0023 (4)	0.0041 (4)	0.0012 (4)
B3	0.0177 (5)	0.0151 (5)	0.0126 (4)	0.0010 (4)	0.0030 (4)	0.0029 (4)
B4	0.0178 (5)	0.0122 (5)	0.0170 (5)	−0.0008 (4)	0.0062 (4)	0.0019 (4)
B5	0.0168 (5)	0.0138 (5)	0.0148 (5)	−0.0019 (4)	0.0027 (4)	0.0026 (4)
B6	0.0166 (5)	0.0117 (5)	0.0143 (5)	0.0018 (4)	0.0038 (4)	0.0019 (3)
B7	0.0194 (5)	0.0134 (5)	0.0132 (5)	−0.0006 (4)	0.0041 (4)	−0.0003 (4)
B8	0.0182 (5)	0.0133 (5)	0.0160 (5)	0.0030 (4)	0.0056 (4)	0.0025 (4)
B9	0.0170 (5)	0.0112 (5)	0.0174 (5)	0.0016 (4)	0.0041 (4)	0.0015 (4)
B10	0.0168 (5)	0.0127 (5)	0.0138 (5)	0.0019 (4)	0.0031 (4)	0.0022 (4)
N2	0.0364 (6)	0.0262 (6)	0.0183 (5)	−0.0007 (4)	0.0043 (4)	0.0039 (4)
N1	0.0372 (7)	0.0411 (8)	0.0234 (5)	0.0052 (5)	0.0020 (5)	0.0036 (5)
O19A	0.0403 (14)	0.0314 (13)	0.0203 (8)	0.0182 (11)	0.0019 (7)	−0.0025 (7)
O19B	0.068 (5)	0.059 (4)	0.0186 (13)	0.045 (4)	0.0080 (16)	0.0044 (15)

Geometric parameters (Å, º)

O1—B8	1.3478 (14)	O14—B5	1.3761 (14)
O1—B3	1.4751 (14)	O14—B2	1.3801 (14)
O2—B9	1.3879 (14)	O15—B8	1.3602 (14)
O2—B10	1.3893 (14)	O15—H1	0.86 (2)
O3—B6	1.3820 (14)	O16—B4	1.3501 (14)
O3—B8	1.3909 (15)	O16—B7	1.4702 (14)
O4—B1	1.3703 (14)	O17—B4	1.3595 (14)
O4—B2	1.3775 (14)	O17—H11	0.915 (19)
O5—B4	1.3812 (14)	O18—B5	1.3596 (14)
O5—B1	1.3811 (14)	O18—H2	0.82 (2)
O6—B9	1.3673 (15)	B3—O1	1.4751 (14)
O6—H4	0.79 (2)	B8—O1	1.3478 (14)
O7—B10	1.3374 (13)	B10—O9^ii	1.3786 (13)
O7—B7	1.4652 (14)	N2—H6	0.91 (3)
O8—B1	1.3387 (13)	N2—H7	0.81 (4)
O8—B7	1.4652 (15)	N2—H9	0.95 (3)
O9—B10^i	1.3785 (13)	N2—H12	0.92 (4)
O9—B6	1.3813 (14)	N1—H3	0.90 (2)
O10—B2	1.3443 (14)	N1—H5	0.89 (4)
O10—B3	1.4714 (14)	N1—H8	0.87 (3)
O11—B6	1.3399 (13)	N1—H10	0.94 (4)
O11—B3	1.4638 (14)	O19A—O19B	0.824 (10)
O12—B5	1.3536 (14)	O19A—H13	0.95 (3)
O12—B3	1.4699 (15)	O19A—H14	0.85 (3)
O13—B9	1.3424 (14)	O19B—H13	0.95 (3)
O13—B7	1.4676 (15)	O19B—H14	0.99 (3)
B8—O1—B3	122.98 (9)	O11—B6—O3	121.99 (10)
B9—O2—B10	118.24 (9)	O11—B6—O9	122.87 (10)
B6—O3—B8	118.28 (9)	O3—B6—O9	115.12 (9)
B1—O4—B2	131.70 (9)	O8—B7—O7	109.49 (9)
B4—O5—B1	118.28 (9)	O8—B7—O13	108.17 (9)
B9—O6—H4	113.7 (15)	O7—B7—O13	111.01 (8)
B10—O7—B7	123.35 (9)	O8—B7—O16	111.85 (8)
B1—O8—B7	122.68 (9)	O7—B7—O16	107.78 (9)
B10^i—O9—B6	128.86 (8)	O13—B7—O16	108.55 (9)
B2—O10—B3	122.74 (9)	O1—B8—O15	124.06 (10)
B6—O11—B3	123.53 (9)	O1—B8—O15	124.06 (10)
B5—O12—B3	122.13 (9)	O1—B8—O3	121.04 (10)
B9—O13—B7	123.16 (9)	O1—B8—O3	121.04 (10)
B5—O14—B2	118.57 (9)	O15—B8—O3	114.87 (10)
B8—O15—H1	118.2 (14)	O13—B9—O6	118.27 (10)
B4—O16—B7	122.04 (8)	O13—B9—O2	121.38 (10)
B4—O17—H11	112.3 (12)	O6—B9—O2	120.32 (9)
B5—O18—H2	118.2 (12)	O7—B10—O9^ii	123.43 (10)
O8—B1—O4	123.93 (10)	O7—B10—O2	121.74 (10)
O8—B1—O5	121.72 (9)	O9^ii—B10—O2	114.79 (9)
O4—B1—O5	114.32 (9)	H6—N2—H7	109 (3)
O10—B2—O4	124.50 (10)	H6—N2—H9	108 (2)
O10—B2—O14	121.78 (10)	H7—N2—H9	105 (3)
O4—B2—O14	113.72 (9)	H6—N2—H12	123 (3)
O11—B3—O12	107.65 (9)	H7—N2—H12	111 (3)
O11—B3—O10	109.84 (9)	H9—N2—H12	100 (3)
O12—B3—O10	111.80 (8)	H3—N1—H5	114 (3)
O11—B3—O1	110.82 (8)	H3—N1—H8	109 (2)
O12—B3—O1	108.62 (9)	H5—N1—H8	112 (3)
O10—B3—O1	108.12 (9)	H3—N1—H10	113 (2)
O11—B3—O1	110.82 (8)	H5—N1—H10	91 (3)
O12—B3—O1	108.62 (9)	H8—N1—H10	118 (3)
O10—B3—O1	108.12 (9)	O19B—O19A—H13	64.5 (17)
O16—B4—O17	118.73 (9)	O19B—O19A—H14	72.3 (17)
O16—B4—O5	121.70 (10)	H13—O19A—H14	99 (2)
O17—B4—O5	119.54 (10)	O19A—O19B—H13	64.0 (18)
O12—B5—O18	122.17 (10)	O19A—O19B—H14	55.2 (16)
O12—B5—O14	121.94 (10)	H13—O19B—H14	90 (2)
O18—B5—O14	115.89 (9)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O15—H1···O6^iii	0.86 (2)	2.06 (2)	2.846 (1)	153 (2)
O18—H2···O17^iv	0.82 (2)	1.85 (2)	2.637 (1)	158 (2)
N1—H3···O4^v	0.90 (2)	2.16 (2)	3.039 (2)	168 (2)
O6—H4···O10^vi	0.79 (2)	2.29 (2)	2.991 (2)	147 (2)
N1—H5···O11^ii	0.89 (4)	2.38 (4)	3.231 (2)	159 (3)
N2—H6···O18^vii	0.91 (3)	1.83 (3)	2.745 (2)	179 (2)
N2—H7···O7^i	0.81 (4)	2.22 (3)	2.992 (2)	160 (3)
N1—H8···O15^viii	0.87 (3)	2.22 (3)	2.909 (2)	136 (3)
N2—H9···O12^ix	0.95 (3)	2.24 (3)	3.117 (2)	154 (2)
N1—H10···O16^iii	0.94 (4)	2.22 (4)	3.098 (2)	154 (3)
O17—H11···O19A^v	0.92 (2)	1.70 (2)	2.576 (2)	160 (2)
O19A—H14···O13^iii	0.85 (3)	1.87 (3)	2.710 (2)	170 (3)
N2—H12···O2^vi	0.92 (4)	2.04 (4)	2.945 (2)	165 (3)
O19A—H13···O1	0.95 (3)	1.81 (3)	2.693 (2)	153 (3)

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