{2-Hydroxy-6-[(2-oxidophenyl)iminomethyl-κ2 N,O]phenolato-κO 1}phenylboron

The [4.3.0]heterobicyclic title structure, C19H14BNO3, is composed of a five-membered OBNC2 ring and a six-membered OBNC3 ring, each of which has an approximate envelope conformation. The coordination geometry of the B atom is distorted tetrahedral. In the crystal structure, centrosymmetrically related molecules are associated through pairs of O—H⋯O hydrogen bonds.

We have synthesized the [4.3.0]heterobicycle (I), Fig. 1 et al., 1998;Barba et al., 2001); however, the sum of bond lengths at the boron atom is significantly shorter for (I) (6.15 versus 6.18 Å), indicating that there is a small, but systematic tendency for bond length shortening.
The degree of π-delocalization between the aromatic rings connected by the imino group can be analyzed by the C-N-C-C torsion angles (Reyes et al., 2005;Lamère et al., 2006;Muñoz et al., 2008). The C7-N1-C8-C13 torsion angle has a value of 26.1 (4) ° indicating that the π-delocalization is distorted. The distortion can be evidenced also by the In the crystal structure, neighboring molecules are associated through O3-H···O2 i hydrogen bonds [symmetry code: (i), -x, 2-y, 1-z] to form supramolecular dimeric units having crystallographic inversion symmetry (Fig. 2). The crystal packing is further stabilized by C-H···O interactions (Table 1).

Experimental
For the preparation of (I), 2,3-dihydroxysalicylaldehyde (0.250 g, 1.81 mmol), 2-aminophenol (0.198 g, 1.81 mmol) and phenylboronic acid (0.221 g, 1.81 mmol) were dissolved in DMF (35 ml), and the solution was refluxed for 1 h in the presence of a Dean-Stark trap. After cooling, the product precipitated in the form of a yellow crystalline solid, which was filtered and washed with hexane. Yield: 0.102 g (18 %). M.pt. 531 K.

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.