Synthesis and Structural Characterization of Neutral and Cationic Alkylaluminum Complexes Based on Bidentate Aminophenolate Ligands

Abstract

The reaction of the aminophenols 2-(CH2L)-6-R-C6H3OH (R = Ph, L = NMe2, 1a; R = tBu, L = NMe2, 1b; R = tBu, L = NC4H8, 1c; R = tBu, L = NC5H10, 1d) with 1 equiv of AlMe3 affords the corresponding dimethyl Al complexes {2-(CH2L)-6-R-C6H3O}AlMe2 (R = Ph, L = NMe2, 2a; R = tBu, L = NMe2, 2b; R = tBu, L = NC4H8, 2c; R = tBu, L = NC5H10, 2d) in high yields. Compounds 2a−d appear to be monomeric, on the basis of X-ray analysis for 2b,d and NMR data for 2a−d, and are stable in the presence of THF. {2-(CH2NMe2)-6-Ph-C6H3O}AlMe2 (2a) cleanly reacts with B(C6F5)3 to yield the dinuclear cationic Al species 3a+. X-ray diffraction analysis shows that the cation 3a+ can be seen as an adduct of the three-coordinate cation {2-(CH2NMe2)-6-Ph-C6H3O}AlMe+ and the neutral precursor 2a, in which the two Al centers are connected via a μ2-O aminophenolate bridge. Similarly, the reaction of Al dimethyl complexes 2b−d with B(C6F5)3 yields dinuclear cationic Al species 3b−d+/3b‘−d‘+ (3b+/3b‘+ in a 1/1 ratio; 3c,d+/3c‘,d‘+ in a 3/1...