Salen-supported dinuclear and trinuclear boron compounds

Six boron compounds have been synthesized through the combination of phenylboronic acid and various Salen (N,N′-ethylenebis(2-hydroxy)benzylidenimine) ligands. They contain seven- and eight-membered heterocycles with a bridging oxygen and have the formula: L[(PhB)2(μ-O)] (L=Acmen (1), Salen(tBu) (2), Sal(2-OH)pen (3), Salpen(tBu) (4), Acpen (5)) and L[B2(μ-O)(O2BPh)] (L=Acen (6), Salmen (7)). Compounds 6 and 7 are interesting trinuclear boron derivatives with two four-coordinate and one three-coordinate boron atoms. The compounds have been characterized by MP, MS, IR, EA and 1H- and 11B-NMR, by 11B-MAS for 6 and 7 and by X-ray crystallography for 2, 4–7.