Aluminum Borohydrides with Acenaphthene-1,2-diimine Ligands

The reactions of BH 3 ·NHMe 2 with hydrides [(dpp-Bian)Al(H) 2 Li(THF) 3 ] ( 1·THF ) and [(dpp-Bian)Al(H) 2 Li(Et 2 O) 2 ] ( 1·Et 2 O ) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) proceed with the deprotonation of BH 3 ·NHMe 2 and result in bimetallic borohydrides [(dpp-Bian)Al(H)NMe 2 BH 3 Li(THF) 2 ] ( 2 ) and [dpp-bianAl(H)NMe 2 BH 3 Li(Et 2 O)] 2 ( 3 ), respectively. The hydrides 1·THF and 1·Et 2 O serve as catalysts for the dehydrocoupling of BH 3 ·NHMe 2 . The reactions of 1·THF and 1·Et 2 O with two equivalents of BH 3 ·SMe 2 led to LiBH 4 elimination and the formation of aluminum borohydrides [(dpp-Bian)Al(BH 4 )(solv)] ( 5·THF, solv = THF; 5·Et 2 O, solv = Et 2 O). The sterically hindered hydride [(Ar BIG -Bian)AlH(THF)] ( 7 ) (Ar BIG -Bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) also reacts with BH 3 ·SMe 2 to give the aluminum borohydride [(Ar BIG -Bian)Al(BH 4 )(THF)] ( 8 ), which in turn induces a reductive opening of the tetrahydrofuran molecule to give the compound [Ar BIG -BianAl(O n Bu)(THF)] ( 9 ). Complexes 2, 3, 5, 8, and 9 have been characterized by infrared and nuclear magnetic resonance spectroscopies, and molecular structures of 2, 3, 5·Et 2 O, and 9 were determined by single-crystal X-ray analysis.