(4-Carbamoylphenyl)boronic acid

In the title compound, C7H8BNO3, the molecule lies on an inversion center leading to a statistical disorder of the B(OH)2 and CONH2 groups. In the crystal structure, molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming sheets parallel to the bc plane. The B(OH)2 and CONH2 groups are twisted out of the mean plane of the benzene ring by 23.9 (5) and 24.6 (6)°, respectively.

In the title compound, C 7 H 8 BNO 3 , the molecule lies on an inversion center leading to a statistical disorder of the B(OH) 2 and CONH 2 groups. In the crystal structure, molecules are linked by N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, forming sheets parallel to the bc plane. The B(OH) 2 and CONH 2 groups are twisted out of the mean plane of the benzene ring by 23.9 (5) and 24.6 (6) , respectively.

Comment
The title compound possesses two distinct functional groups: boronic acid and amide. Compounds containing the boronic acid moiety are important as precursors for organic transformations (Miyaura & Suzuki, 1995;Suzuki, 1999;) and recently attention has been focused on these types of compounds as potential pharmaceutical agents (Adams & Kauffman, 2004;Barth et al., 2005;Minkkilä et al., 2008). Amides are versatile precursors to many other functional groups and undergo many chemical reactions, usually through an attack on the carbonyl group. The title compound is a commercial product and we solved its crystal structure to verify the repeatability of the weak interactions already observed in the structures of terephthalamide and phenylboronic acid Cobbledick & Small, 1972;Rodríguez-Cuamatzi, P. et al., 2004. Self assembling based on hydrogen-bonding motifs is of general interest for crystal engineering, structural chemistry and biology (Maly et al., 2006;Desiraju, 1995).
The crystal structure of the studied compound contains molecules linked together by hydrogen bonds in sheets similar to those of terephthalamide (Cobbledick & Small, 1972) and 1,4-phenilboronic acid (Rodríguez-Cuamatzi et al., 2004) (Fig.   1). More over all tree compounds have similar triclinic lattice parameters and crystallize in the centrosymmetric P-1 space group. In the title compound, the location of the molecule on a center of symmetry leads to a statistical disorder of the B(OH) 2 and CONH 2 groups (Fig. 1). The B(OH) 2 and CONH 2 groups are out of the mean plane of the benzene ring by 23.9 (5)° and 24.6 (6)° respectively. Similar angle is reported for the amide group in terephthalamide (23°) while the one for 1,4 phenilboronic acid is greater (~35°). It should be noted that C-C (phenyl-amide) and C-B distances of 1.505 (6) Å and 1.546 (6)Å are restrained to match those in the terephthalamide molecule C-C (phenyl-amide) distance of 1.489 (5) Å and that of the 1,4-phenilboronic acid molecule with C-B of 1.564 (3) Å.
Both amide and boronic acid groups are involved in hydrogen bonds to form ring motifs marked by I and II (Fig. 2).
Type I, R 2 2 (8) (Bernstein et al. 1995) connects opposite sides of molecules to chains. Type II links the chains to form sheets parallel to bc. However, two type of motifs linking the chains can be proposed: R 4 4 (8) (Fig. 2a) and R 3 4 (8) (Fig. 2b). Indeed, hydrogen bonding pattern can vary depending on the position of the hydrogen atoms attached to the B(OH) 2 moiety (Fig. 3). The current position of H atoms for the B(OH) 2 group (syn, anti) results from a SHELX AFIX 147 instruction.
As a result the bonding interaction between the B(OH) 2 and amide groups is forbidden, due to the short contact between hydrogen atoms linked to O1 and N1 (H1···H1A 1.272 Å). Thus the hydrogen bonding interactions in the chains are limited to "boronic-boronic" and "amid-amide". An alternative (anti, syn) positioning for H attached to O will permit hydrogen bonding between B(OH) 2 and amid groups but an F o map (Fig. 4) does not suggest an (anti, syn) conformation for the H atoms.

Experimental
The studied compound is a commercial product (Frontier Scientific). Colorless crystals of C 7 H 8 NBO 3 , were obtained after several days staying from 50% water:ethanol solution at 277K.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )
x y z U iso */U eq Occ. (