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-l,4,7-triazcyclononane; L2 = l-(2-hydroxy- 2-methylethyl)-4,7-diisopropyl-1,4,7-triazacyclononane].
