An unprecedented coordination mode for hemilabile pendant-arm 1,4,7-triazacyclononanes and the synthesis of cationic organoaluminium complexes

Abstract

Reaction of AlMe₃ or [AlMe₃·py] with the pendant arm OH-funtionalised 1,4,7-triazacyclononane proligands, HL¹ or HL², affords the four- and five-coordinate derivatives [Al(L¹)Me₂] 1 or [Al₂(L²)₂Me₄] 2 in which the pendant alkoxide O-donor and only one macrocycle N-donor is bound to Al; methyl anion abstraction from 1 yields cationic, pentacoordinate [Al(L¹)Me]⁺ in which L¹ has a tetradentate coordination mode [L¹ = 1-(2-hydroxy-3,5-di-tert-butylbenzyl)-4,7-diisopropyl-1,4,7-triaz cyclononane; L² = 1-(2-hy- droxy-2-methylethyl)-4,7-diisopropyl-1,4,7-triazacyclononane].