Organo-aluminium and -gallium complexes with ω-NH-functional alkoxide ligands

Abstract

The aminoalcohols MeNH(CH₂)₂OH (1), ^tBuNH(CH₂)₂OH (2), MeNH(CH₂)₃OH (3), ^tBuNH(CH₂)₃OH (4) and MeNHCH₂CMe₂CH₂OAlMe₂ (5) have been reacted with AlMe₃ to give the five corresponding aminoalkoxides of the general formula RNH–X–AlMe₂1a–5a (X = organic spacer between N and O). ^tBuNHCH₂CMe₂CH₂OH (6) reacts with AlMe₃ to give [^tBuNHCH₂CMe₂CH₂OAlMe₂]·AlMe₃ (6a·AlMe₃). Analogous reactions of the aminoalcohols 1, 2, 3 and 4 with Al^tBu₃, GaMe₃ and Ga^tBu₃ afforded the corresponding aminoalkoxides of the general formula RNH–X–MR′₂1b–4b (MR′₂ = Al^tBu₂), 1c–4c (MR′₂ = GaMe₂) and 1d–4d (MR′₂ = Ga^tBu₂). The compounds were characterised by NMR spectroscopy, elemental analyses and mass spectrometry. Crystal structures were determined for 3a, 5a, 6a·AlMe₃, 3c, 3d, 2d and 4d. Compounds 3a and 5a dimerise via Al₂O₂ rings, while the amino-functions form intramolecular Al–N bonds. Compounds 3c and 3d form monomers with intramolecular Ga–N bonds. Compounds 2d and 4d are dimers via Ga₂O₂ rings but in contrast to 3a and 5a without formation of intramolecular Ga–N bonds. 6a·AlMe₃ also forms a monomeric compound with intramolecular AlN bond and a further AlMe₃ unit bonded to the O atom. The dynamic behaviour of 1d and 2d was investigated by variable-temperature NMR spectroscopy. Some compounds have different aggregation in solid and fluid phases.