2-Methoxy-3-(trimethylsilyl)phenylboronic acid

The molecular structure of the title compound, C10H17BO3Si, features an intramolecular O—H⋯O hydrogen bond; the boronic group group has an exo–endo conformation. In the crystal, the molecules interact with each other by O—H⋯O hydrogen bonds, producing centrosymmetric dimers that are linked by weak π–π stacking interactions featuring specific short B⋯C contacts [e.g. 3.372 (2) Å], forming an infinite columnar structure aligned along the a-axis direction.

Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: PLATON (Spek, 2009). The X-ray measurements were undertaken in the Crystallographic Unit of the Physical Chemistry Laboratory at the Chemistry Department of the University of Warsaw. This work was supported by the Warsaw University of Technology. The support by Aldrich Chemical Co., Milwaukee, WI, USA, through continuous donation of chemicals and equipment is gratefully acknowledged.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK5273).

Synthesis and crystallization
The preparation of the title compound (I) was described previously (Durka et al., 2010). Crystals suitable for singlecrystal X-ray diffraction analysis were grown by slow evaporation of an acetone solution of (I).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. All hydrogen atoms were placed in calculated positions with C-H distances of 0.95 Å (phenyl) and 0.98 Å (methyl), and an O-H distance of 0.84 Å, and with U iso (phenyl-H) = 1.2U eq (C), U iso (methyl-H) = 1.5U eq (C) and U iso (hydroxyl-H)=1.5U eq (O).

Results and discussion
The ability of arylboronic acids to form supramolecular structures via hydrogen-bonding interactions of B(OH) 2 groups is well known. The molecular structure of (I) is shown in Fig. 1. The boronic group is only slightly twisted with respect to the benzene ring whereas the methoxy group is twisted almost perpendicularly. The trimethylsilyl group is slightly bent with respect to the aromatic ring. The boronic group has an exo-endo conformation. The endo-oriented OH group is engaged into the intramolecular O-H···O bond with the methoxy O atom to form a six-membered ring typical of structures of related ortho-alkoxyarylboronic acids (Cyrański et al., 2012). The molecules of (I) are linked via almost linear O-H···O bridges to give centrosymmetric dimers. The periodic calculations performed in PIXEL programme (Gavezzotti, 2003) show that the dimer interaction energy is equal to -58.5 kJ/mol, which is comparable to the binding energies of other boronic acids dimers reported in the literature (Cyrański et al., 2008;Durka et al., 2012). The supramolecular architecture in (I) extends through π-π stacking interactions of aromatic rings in the parallel-displaced fashion. The boron atoms are also engaged in these mutual interactions, which is manifested by a relatively short B1···C2 contact of 3.372 (2) Å. Short B1···C2 interactions were described in more detail for the structures of fluorinated 1,4phenylenediboronic acids (Durka et al., 2012). Thus, another centrosymmetric motif can be distinguished. The interaction energy of such dimers amounts to -33.5 kJ/mol. As a result of H-bonding and π-π interactions, a specific columnar network is formed in the a axis direction (Figs 2 & 3). The total cohesive energy calculated for asymmetric unit equals to -111.7 kJ/mol. In conclusion, hydrogen-bonding interactions of boronic groups are operative to form centrosymmetric dimeric structure of (I). The extended supramolecular assembly is due to π-π stacking interactions of aromatic rings additionally involving the boron atoms. and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: PLATON (Spek, 2009).

Figure 1
View of the title compound (I) with the atom numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.  Packing diagram viewed along the a axis, indicating the columns of O-H···O and C(π)···B interacting molecules of (I).