Boron complexes of redox-active diimine ligand

Abstract

Boron complexes (dpp-bian)BCl₂ (1) and (dpp-bian)BX (X = Cl, 2; Br, 3) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) have been prepared by reacting mixtures dpp-bian–BX₃ (1 : 1) with one (1) and two (2 and 3) equivalents of sodium correspondingly in toluene. Complexes 2 and 3 reveal a moderate stability against ambient oxygen and moisture. The reaction of complex 2 with PhCCLi gave compound (dpp-bian)B–CCPh (4). Treatment of 2 with potassium hydroxide afforded complexes (dpp-bian)B–OH (5) and (dpp-bian)B–OK (6). Boron amide (dpp-bian)B–NH₂ (7) has been isolated from the reaction of compound 1 with sodium in liquid ammonia. Borane (dpp-bian)B–H (8) can be prepared by the reactions of complexes 2 and 3 with LiAlH₄. Diamagnetic compounds 2–8 have been characterized by IR, ¹H and ¹¹B NMR spectroscopy; paramagnetic complex 1 has been studied by the ESR method. Molecular structures of 2, 5, 7 and 8 have been determined by X-ray crystallography.