VERSATILITY IN PHENOLATE BONDING IN ORGANOALUMINUM COMPLEXES CONTAINING MONO- AND BIS-ORTHO-CHELATING PHENOLATE LIGANDS - X-RAY STRUCTURES OF AL(OC6H2(CH(2)NME(2))(2)-2,6-ME-4)(3), AL(ME)(2)(OC6H2(CH(2)NME(2))(2)-2,6-ME-4)CENTER-DOT-N-ALME(3), AND AL

摘要

The effect of intramolecular coordination on both the structure and the Lewis acidity of aluminum phenolates has been studied. The mono-ortho-amino-substituted phenol HOC6H4(CH(2)NMe(2))-2 (3) reacts with AlMe(3) to produce the substitution products AlMe(3-x), (OC6H4(CH(2)NMe(2))-2)(x) (x = 1 (la), 2 (Ib), and 3 (Ic)) and the trimethylaluminum adduct AlMe(2)(OC6H4(CH(2)NMe(2))-2). O-AlMe(3) (Id), all in high yield. For the bis-ortho-amino-substituted phenol HOC6H2(CH(2)NMe(2))(2)-2,6-Me-4 (4) the substitution products AlMe(3-x) (OC6H2(CH(2)NMe(2))(2)-2,6-Me-4)(x) (x = 2 (2b) and 3 (2c)) were obtained, as well as the mono- and bis(trimethylaluminum) adducts AlMe(2)(OC6H2(CH(2)NMe(2))2-2,6-Me-4). N-AlMe(3) (2d) and AlMe(2)(OC6H2(CH(2)NMe(2))2-2,6-Me-4). N-AlMe(3) . O-AlMe(3) (2e). The mono(phenolate) dimethylaluminum complexes (la and 2a) easily undergo an inter- (la) or an intramolecular (2a) Lewis base induced ligand exchange to give the bis(phenolate) complexes (Ib and 2b, respectively) and trimethylaluminum. The aluminum phenolate complexes were characterized by variable-temperature NMR and single-crystal structure determinations (2c-e). The solid state structure of 2c contains the aluminum surrounded by two bidentate, O,N-bonded, phenolate ligands and one monodentate, O-bonded, phenolate ligand in a trigonal bipyramidal coordination geometry, with the oxygen atoms in the trigonal plane and the two coordinating nitrogen atoms in the apical positions. The molecular structure of 2d contains one AlMe(2) moiety which is bidentate, O,N-coordinated by the phenolate ligand, in a distorted tetrahedral geometry. The second amino substituent forms a Lewis acid-base complex with a molecule AlMe(3), also with a distorted tetrahedral geometry around the aluminum. The structure of 2e is similar to that of 2d but contains an additional molecule of AlMe(3), which forms a Lewis acid-base complex with a lone pair of the phenolate oxygen atom, resulting in a distorted tetrahedral geometry around the aluminum. NMR spectroscopy shows the solution structures to be closely related to those established in the solid state. [References: 46]