Synthesis and structure of hypervalent boron (10-B-5) compounds bearing a 2,6-(p-tolyloxymethyl)benzene tridentate ligand

Abstract

Several organoboron compounds having a tridentate ligand based on 2,6-bis(p-tolyloxymethyl)benzene (5) were prepared. X-ray crystallography revealed that the distances between the central boron and both oxygen atoms of the tridentate ligand varied from 2.50 Å to 3.16 Å. The boron atom of the pinacolato derivative (5a) was found to be tricoordinated, whereas those of the diphenyl (5b) and the catecholato derivative (5c) were pentacoordinated, although these molecular structures were unsymmetrical. Compound 5c was found to have the strongest B–O interactions among this series because the B–O distances of 5c (av. 2.60 Å) are shorter than those for 5b (av. 2.65 Å), and this could mainly come from the electronic effect of the substituents at the boron atom.