Acta Cryst. (2009). E65, m496 [ doi:10.1107/S1600536809012100 ]
![[mu]](/logos/entities/mu_rmgif.gif)
-tetrabutoxyborato]The title compound, [Na(C16H36BO4)]n, has a fourfold axis passing through the Na and B atoms which both are bound by four O atoms. The tetrabutoxyborate anion provides the bridging to form one-dimensional polymers running along [001], just like those found for the tetraethoxyborate structure. The two butoxy `tail' atoms are disordered over two conformations in a 0.887 (9):0.113 (9) ratio.
NaBO2 (5.00 g, 76 mmol) was refluxed in methanol (150 ml) for around 4 h, running the condensate through a bed of molecular sieves before rejoining the reaction flask to remove water liberated from the reaction. The methanol was removed by distillation before adding toluene (80 ml) and n-butanol (80 ml). The solvent volume was reduced to ca 50 ml by distillation, and allowed to cool to room temperature. The colourless product appeared as fine needles, which gradually grew in size over several months in a sealed flask subjected to daily ambient temperature cycles. The needles were filtered under nitrogen, and dried in vacuo. Yield 23.5, (95%). 1H NMR (d8-thf 30°C): δ 1.04, (t, 7.3 Hz, CH3 12H); 1.45, (m, CH2 8H); 1.64, (m, CH2 8H); 3.46, (t, 7.2 Hz, CH2 8H) 13C NMR (CDCl3 30°C): δ 14.80, (CH3); 20.64, (CH2); 36.42, (CH2); 61.12, (OCH2). 11B NMR (d8-thf 30°C): δ 2.78 p.p.m..
In the absence of significant anomalous scattering, the values of the Flack parameter were indeterminate. Accordingly, the Friedel-equivalent reflections were merged prior to the final refinements. The butyl chain carbon atoms C3 & C4 were disordered over two conformations in a final ratio of (unprimed:primed) 0.887:0.113 (9). Three restraints were applied: distances C2–C3, C3–C4, C2—C4 were restrained to be the same for both conformers. Atoms C3' & C4' were refined with a common isotropic U.
All H atoms were constrained to their expected geometries (C—H 0.99, 0.98 Å) except for the latter refinement cycles when the atoms on minor conformer atom C4' were fixed, with a common isotropic thermal parameter. The H atoms on C2 & C3 were refined with isotropic parameters while H atoms on C4 and C3' were refined with Uiso 1.5,1.2 times that of the Ueq of their carrier atoms.
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 and SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).
![[Figure 1]](./bq2133fig1thm.gif)
| Fig. 1. PLATON ORTEP view (Spek, 2009) of the cell contents (30% probability ellipsoids) showing the one-dimensional polymers which run the 4-fold inversion c axis. Only the major conformer C3 & C4 atomic positions are shown for clarity. |
| [Na(C16H36BO4)] | Dx = 1.058 Mg m−3 |
| Mr = 326.25 | Mo Kα radiation, λ = 0.71073 Å |
| Tetragonal, I4 | Cell parameters from 1472 reflections |
| Hall symbol: I -4 | θ = 3.1–31.3° |
| a = 13.3552 (17) Å | µ = 0.09 mm−1 |
| c = 5.7422 (6) Å | T = 112 K |
| V = 1024.2 (2) Å3 | Needle, colourless |
| Z = 2 | 0.80 × 0.32 × 0.10 mm |
| F(000) = 360 |
| Bruker APEXII CCD diffractometer | 906 independent reflections |
| Radiation source: fine-focus sealed tube | 724 reflections with I > 2σ(I) |
| graphite | Rint = 0.027 |
| Detector resolution: 8.333 pixels mm-1 | θmax = 31.5°, θmin = 3.1° |
| φ and ω scans | h = −19→18 |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2003)) | k = −19→18 |
| Tmin = 0.821, Tmax = 0.992 | l = −8→4 |
| 3660 measured reflections |
| 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)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.145 | H-atom parameters constrained |
| S = 1.05 | w = 1/[σ2(Fo2) + (0.0875P)2 + 0.2269P] where P = (Fo2 + 2Fc2)/3 |
| 906 reflections | (Δ/σ)max < 0.001 |
| 66 parameters | Δρmax = 0.28 e Å−3 |
| 3 restraints | Δρmin = −0.20 e Å−3 |
| [Na(C16H36BO4)] | Z = 2 |
| Mr = 326.25 | Mo Kα radiation |
| Tetragonal, I4 | µ = 0.09 mm−1 |
| a = 13.3552 (17) Å | T = 112 K |
| c = 5.7422 (6) Å | 0.80 × 0.32 × 0.10 mm |
| V = 1024.2 (2) Å3 |
| Bruker APEXII CCD diffractometer | 906 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2003)) | 724 reflections with I > 2σ(I) |
| Tmin = 0.821, Tmax = 0.992 | Rint = 0.027 |
| 3660 measured reflections | θmax = 31.5° |
| R[F2 > 2σ(F2)] = 0.049 | H-atom parameters constrained |
| wR(F2) = 0.145 | Δρmax = 0.28 e Å−3 |
| S = 1.05 | Δρmin = −0.20 e Å−3 |
| 906 reflections | Absolute structure: ? |
| 66 parameters | Flack parameter: ? |
| 3 restraints | Rogers parameter: ? |
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. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| Na1 | 0.0000 | 0.5000 | 0.7500 | 0.0311 (4) | |
| O1 | 0.07286 (11) | 0.45588 (11) | 0.4120 (2) | 0.0321 (4) | |
| C1 | 0.15761 (19) | 0.4090 (2) | 0.3117 (4) | 0.0454 (6) | |
| H1A | 0.1934 | 0.4573 | 0.2106 | 0.086 (13)* | |
| H1B | 0.1359 | 0.3518 | 0.2144 | 0.083 (13)* | |
| C2 | 0.2267 (2) | 0.3726 (2) | 0.5005 (5) | 0.0490 (7) | |
| H2A | 0.2829 | 0.3356 | 0.4284 | 0.092 (15)* | |
| H2B | 0.1899 | 0.3254 | 0.6022 | 0.073 (11)* | |
| C3 | 0.2693 (2) | 0.4582 (3) | 0.6508 (7) | 0.0527 (10) | 0.887 (9) |
| H3A | 0.2989 | 0.5098 | 0.5480 | 0.069 (12)* | 0.887 (9) |
| H3B | 0.2141 | 0.4898 | 0.7394 | 0.050 (9)* | 0.887 (9) |
| C4 | 0.3485 (2) | 0.4210 (4) | 0.8197 (8) | 0.0682 (13) | 0.887 (9) |
| H4A | 0.3205 | 0.3671 | 0.9155 | 0.102* | 0.887 (9) |
| H4B | 0.3699 | 0.4762 | 0.9204 | 0.102* | 0.887 (9) |
| H4C | 0.4062 | 0.3956 | 0.7323 | 0.102* | 0.887 (9) |
| B1 | 0.0000 | 0.5000 | 0.2500 | 0.0279 (8) | |
| C3' | 0.252 (3) | 0.395 (3) | 0.748 (4) | 0.087 (10)* | 0.113 (9) |
| H3'1 | 0.2743 | 0.3337 | 0.8282 | 0.105* | 0.113 (9) |
| H3'2 | 0.1924 | 0.4218 | 0.8298 | 0.105* | 0.113 (9) |
| C4' | 0.336 (3) | 0.473 (3) | 0.750 (8) | 0.087 (10)* | 0.113 (9) |
| H4'1 | 0.3076 | 0.5348 | 0.6716 | 0.13 (11)* | 0.113 (9) |
| H4'2 | 0.3929 | 0.4510 | 0.6891 | 0.13 (11)* | 0.113 (9) |
| H4'3 | 0.3431 | 0.4948 | 0.9211 | 0.13 (11)* | 0.113 (9) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Na1 | 0.0425 (6) | 0.0425 (6) | 0.0082 (6) | 0.000 | 0.000 | 0.000 |
| O1 | 0.0386 (8) | 0.0456 (8) | 0.0120 (5) | 0.0083 (6) | −0.0005 (5) | −0.0011 (6) |
| C1 | 0.0477 (13) | 0.0700 (17) | 0.0186 (9) | 0.0186 (12) | −0.0007 (8) | −0.0077 (9) |
| C2 | 0.0465 (13) | 0.0701 (16) | 0.0304 (11) | 0.0187 (11) | −0.0042 (11) | −0.0067 (12) |
| C3 | 0.0473 (17) | 0.060 (2) | 0.0508 (18) | −0.0018 (13) | −0.0073 (14) | −0.0031 (15) |
| C4 | 0.0479 (17) | 0.101 (3) | 0.055 (2) | 0.0221 (19) | −0.0186 (17) | −0.029 (2) |
| B1 | 0.0365 (12) | 0.0365 (12) | 0.0106 (14) | 0.000 | 0.000 | 0.000 |
| Na1—O1i | 2.2496 (14) | C3—H3B | 0.9900 |
| Na1—O1ii | 2.2496 (14) | C4—H4A | 0.9800 |
| Na1—O1 | 2.2496 (14) | C4—H4B | 0.9800 |
| Na1—O1iii | 2.2496 (14) | C4—H4C | 0.9800 |
| O1—C1 | 1.416 (3) | B1—O1iv | 1.4696 (14) |
| O1—B1 | 1.4696 (14) | B1—O1v | 1.4696 (14) |
| C1—C2 | 1.505 (3) | B1—O1ii | 1.4696 (14) |
| C1—H1A | 0.9900 | B1—Na1vi | 2.8711 (3) |
| C1—H1B | 0.9900 | C3'—C4' | 1.531 (19) |
| C2—C3' | 1.49 (2) | C3'—H3'1 | 0.9900 |
| C2—C3 | 1.541 (4) | C3'—H3'2 | 0.9900 |
| C2—H2A | 0.9900 | C4'—H4'1 | 1.01 (4) |
| C2—H2B | 0.9900 | C4'—H4'2 | 0.89 (5) |
| C3—C4 | 1.519 (5) | C4'—H4'3 | 1.03 (4) |
| C3—H3A | 0.9900 | ||
| O1i—Na1—O1ii | 138.10 (5) | C4—C3—C2 | 111.8 (3) |
| O1ii—Na1—O1 | 60.75 (7) | C4—C3—H3A | 109.3 |
| C1—O1—B1 | 116.68 (14) | C2—C3—H3A | 109.3 |
| C1—O1—Na1 | 144.35 (13) | C4—C3—H3B | 109.3 |
| B1—O1—Na1 | 98.90 (7) | C2—C3—H3B | 109.3 |
| O1—C1—C2 | 109.89 (19) | H3A—C3—H3B | 107.9 |
| O1—C1—H1A | 109.7 | O1iv—B1—O1v | 101.44 (11) |
| C2—C1—H1A | 109.7 | O1iv—B1—O1ii | 113.63 (6) |
| O1—C1—H1B | 109.7 | C2—C3'—C4' | 108 (2) |
| C2—C1—H1B | 109.7 | C2—C3'—H3'1 | 110.1 |
| H1A—C1—H1B | 108.2 | C4'—C3'—H3'1 | 110.1 |
| C3'—C2—C1 | 139.4 (17) | C2—C3'—H3'2 | 110.1 |
| C1—C2—C3 | 112.9 (2) | C4'—C3'—H3'2 | 110.1 |
| C3'—C2—H2A | 109.2 | H3'1—C3'—H3'2 | 108.4 |
| C1—C2—H2A | 109.0 | C3'—C4'—H4'1 | 106 (3) |
| C3—C2—H2A | 109.0 | C3'—C4'—H4'2 | 113 (3) |
| C3'—C2—H2B | 71.4 | H4'1—C4'—H4'2 | 115 (5) |
| C1—C2—H2B | 109.0 | C3'—C4'—H4'3 | 105 (3) |
| C3—C2—H2B | 109.0 | H4'1—C4'—H4'3 | 104 (3) |
| H2A—C2—H2B | 107.8 | H4'2—C4'—H4'3 | 113 (4) |
| O1i—Na1—O1—C1 | 45.7 (3) | C1—C2—C3—C4 | −172.9 (3) |
| O1ii—Na1—O1—C1 | 176.4 (3) | C1—O1—B1—O1iv | 60.0 (2) |
| O1iii—Na1—O1—C1 | −52.8 (3) | Na1—O1—B1—O1iv | −122.34 (3) |
| O1i—Na1—O1—B1 | −130.79 (7) | C1—O1—B1—O1v | −55.3 (2) |
| O1ii—Na1—O1—B1 | 0.0 | C1—O1—B1—O1ii | −177.7 (2) |
| B1—O1—C1—C2 | 177.19 (19) | Na1—O1—B1—O1ii | 0.0 |
| Na1—O1—C1—C2 | 1.1 (4) | C1—O1—B1—Na1vi | 2.3 (2) |
| O1—C1—C2—C3' | −25.0 (19) | Na1—O1—B1—Na1vi | 180.0 |
| O1—C1—C2—C3 | −63.0 (3) | C1—O1—B1—Na1 | −177.7 (2) |
| Symmetry codes: (i) −y+1/2, x+1/2, −z+3/2; (ii) −x, −y+1, z; (iii) y−1/2, −x+1/2, −z+3/2; (iv) y−1/2, −x+1/2, −z+1/2; (v) −y+1/2, x+1/2, −z+1/2; (vi) x, y, z−1. |
We thank Drs J. Wikaira & C. Fitchett of the University of Canterbury, New Zealand, for their assistance.
Allen, F. H. (2002). Acta Cryst. B58, 380–388.
Bishop, M., Bott, S. G. & Barron, A. R. (2000). J. Chem. Soc. Dalton Trans. pp. 3100–3105.
Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Caselli, A., Solari, E., Scopelliti, R., Floriana, C., Re, N., Rizoli, C. & Chiesi-Villa, A. (2000). J. Am. Chem. Soc. 122, 3652–3670.
Gainsford, G. J. & Kemmitt, T. (2004). Acta Cryst. E60, m1943–m1944.
Gainsford, G. J. & Kemmitt, T. (2005). Acta Cryst. C61, m417–m418.
Kemmitt, T. & Gainsford, G. J. (2009). Int. J. Hydrogen Energ. Submitted.
Sheldrick, G. M. (2003). SADABS. University of Göttingen, Germany.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Spek, A. L. (2009). Acta Cryst. D65, 148–155.
Zviedre, I. I. & Belsky, V. K. (2001). Latv. Khim. Z. (Latvian J. Chem.), 1, 91–92.
This study is part of a program aimed at investigating boron diolates and alkoxides with potential applications in hydrogen storage/recycling systems (Kemmitt & Gainsford, 2009). Several other related compounds have been reported [Gainsford & Kemmitt, 2004 (GAKLAG); Gainsford & Kemmitt, 2005 (KASSUT); Bishop et al., 2000 (ABAYUX, ABAZEI)]. There are no reported structures for tetrabutoxyborate salts (Allen, 2002), though there are a large number of tetramethoxyborate salts reported (see Gainsford & Kemmitt, 2005).
The basic polymeric fragment of the title compound, with asymmetric unit formula [Na0.25(C4H9B0.25O), has 4-fold inversion crystallographic symmetry with the symmetry (c) axis passing through the Na & B atoms. Enantiomeric resolution was not expected from the synthesis and it could not be obtained using anomalous dispersion effects.
The sodium cations are four-coordinate in a highly distorted tetrahedral arrangement with mean Na–O 2.2496 (14)Å and O–Na–O angles of 138.10 (5) and 60.75 (7) compared with 138.18 (8) and 60.62 (12)° in analogous tetraethoxyborato structure KASSUT Gainsford & Kemmitt, 2005 C). This Na—O distance is shorter than those reported when the bound O atoms atoms are not structurally constrained; one example of the latter case is POGDAQ01 (Caselli et al. (2000)) where Na–O range from 2.243–2.355Å in a niobium-tetraoxycallix(4)arene compound.
The B—O and C—O bond lengths average to 1.416 (4) and 1.467 (4)Å, and the B—O—C angle mean is 117.8 (2)°, values that fall within normal ranges as reported before in GAKLAG (Gainsford & Kemmitt, 2004). The O—B—O angles are distorted from pure tetrahedral values (101.45 (7) & 113.62 (8)°) somewhat more than those in the bis(1,1,1-trihydroxymethylpropane)borate salt (XOCHOM, Zviedre & Belsky, 2001) of 108.6–109.9°. The borate anions bridge the sodium cations making one-dimensional polymers running along the 4-fold inversion symmetry c axis direction (Fig. 1). This packing mode was also observed in catena-(µ3bis(ethylenedioxy)borato)- sodium(I)) (GAKLAG, Gainsford & Kemmitt, 2004) where the polymers were aligned with the 21 screw axis.