Structural studies of organoboron compounds. XXV. Synthesis and structure of (maltolato)diphenylboron
The reaction of maltol (3-hydroxy-2-methyl-4-pyrone) with diphenylborinic acid affords a high yield of the title compound. Crystals of (maltolato)diphenylboron are monoclinic, a = 14.3481(6), b = 8.3994(3), c = 12.6657(5) Å, β = 100.892(4)°, Z = 4, space group P21/n. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.041 and Rw = 0.052 for 2052 reflections with I ≥ 3σ(1). The molecule contains a five-membered C2O2B ring having a flattened B-envelope conformation, the B atom being displaced 0.081(2) Å from the C2O2 plane. Structural and spectroscopic data are consistent with weak binding of the maltolate oxygen atoms to boron. Bond distances (corrected for libration) are O—B = 1.533(2) and 1.600(3), B—C = 1.600(3) and 1.605(3) Å.