Synthesis of an eight-membered Al2B2O4 – Ring with two aluminum atoms each in a spiro center

The reaction of LAlH2 (L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) (1) with cyclopentylboronic acid resulted in the boroxine-linked aluminum compound LAl[OB(C5H9)]2(μ-O) (2). However, the reaction of 1 with 3-hydroxymethylphenylboronic acid gave an eight-membered boroxine-linked dialuminum compound of composition [LAlOB(3-OHCH2C6H4)]2 (3) with a spiro center at each of the aluminum atoms. The two complexes were characterized by 1H NMR, IR spectroscopy, elemental analysis, and single crystal X-ray structural analysis.