Alcohol and secondary amine complexes of tri-tert-butylaluminium: enhanced stability through intramolecular hydrogen bonding

Abstract

Reaction of Al(Bu t ) 3 with between 1 and 2 equivalents of HOCH 2 CH 2 CH 2 NMe 2 allows for the isolation of the Lewis acid-base complex, (Bu t ) 3 Al[O(H)CH 2 CH 2 CH 2 NMe 2 ] 1, which undergoes alkane elimination above 45 ЊC to yield [(Bu t ) 2 Al(µ-OCH 2 CH 2 CH 2 NMe 2 )] 2 2. Compound 2 is also formed directly when 2 equivalents of Al(Bu t ) 3 react with 1 equivalent of HOCH 2 CH 2 CH 2 NMe 2 . The molecular structure of 1 shows an Al᎐O bond distance comparable to that found in the bridging alkoxide compounds 2 and [(Bu t ) 2 Al(µ-OPr n )] 2 3, suggesting that the Al᎐O ؒ ؒ ؒ H unit may be considered analogous to a bridging alkoxide unit, Al(µ-OR)Al, as a consequence of a significant contribution from the zwitterionic alkoxide Ϫ /ammonium ϩ form made possible by a strong intraligand hydrogen bond. The kinetics of the conversion of 1 into 2 have been studied. A large activation energy and positive deuterium isotope effect are consistent with breaking of the hydrogen bond during the transition state. The reaction of (Bu t ) 3 Al(NMe 3 ) 4 with ethanol yields [(Bu t ) 2 Al(µ-OEt)] 2 5. The reaction of Al(Bu t ) 3 with HN(Me)(CH 2 ) n NMe 2 (n = 3 or 2) yields the stable Lewis acid-base adducts (Bu t ) 3 Al[NH(Me)CH 2 CH 2 CH 2 NMe 2 ]

Synthesis of a base-stabilized alumoxane: preferential hydrolysis of an aluminium–amido over an aluminium–alkyl

“…10 Subsequently, we have reported a similar synthesis for the first example of a structurally characterized tetraalkylalumoxane, [( t Bu) 2 Al(py)] 2 (µ-O) III. 11 The molecular structure of 13 The hydrolytic protonation of the amide nitrogen, rather than one of the tert-butyl groups, follows our previous observ-ations that the presence of a heteroatom donor ligand (e.g., alkoxide, aryloxide, amide, etc.) significantly reduces the basicity of the aluminium alkyl group.…”

Polyethylene/MMT nanocomposites prepared by in situ polymerization using supported catalyst systems

“…From the above observations, it was considered that MMAO cocatalyst was supported by the reaction to hydroxyl group of layer surface [10]. The removal of amine modifier could be understood by the reaction of oxygen atoms of MMAO with the ammonium ions to form the zwitterions of alkoxide anion/ammonium cation as suggested by Barren [11]. According to his interpretation the zwitterion can be transferred to a non-hydrogen bonded intermediate and will presumably then undergo the rapid alkane elimination to yield amine.…”

Hydrogen/Deuterium Exchange Catalyzed by an Unusually Stable Mercury–Toluene Complex

“…[5] Thus, the activation of aromatic compounds by mercury salts is well established. Our interest in this area was initially stimulated by the possibility of exploring the activation of small molecules by Lewis acids, [6,7] in particular the use of Group 13 halides to enhance the Lewis acidity of other metal halides, for example, mercury.…”