Trimethylaluminum finds widespread applications in chemical and materials synthesis, most prominently in its partially hydrolyzed form of methylalumoxane (MAO), which is used as a cocatalyst in the polymerization of olefins. This work investigates the sequential reactions of trimethylaluminum with hexaprotic phosphazenes (RNH)(6)P3N3 (=XH6) equipped with substituents R of varied steric bulk including tert-butyl (1H(6)), cyclohexyl (2H(6)), isopropyl (3H(6)), isobutyl (4H(6)), ethyl (5H(6)), propyl (6H(6)), methyl (7H(6)), and benzyl (8H(6)). Similar to MAO, the resulting complexes of polyanionic phosphazenates [XHn](n-6) accommodate multinuclear arrays of [AlMe2](+) and [AlMe](2+). Reactions were monitored by P-31 NMR spectroscopy, and structures were determined by single-crystal X-ray diffraction. They included 1H(4)(AlMe2)(2), 1H(3)(AlMe2)(3), 2H(3)(AlMe2)(3), 3(AlMe2)(4)AlMe, 4H(AlMe2)(5), 4(AlMe2)(6), {5H(AlMe2)(4)}(2)AlMe, 5(AlMe2)(6), 6(AlMe2)(6), {7(AlMe2)(4)AlMe}(2), and 8(AlMe2)(6). The study shows that subtle variations of the steric properties of the R groups influence the reaction pathways, levels of aggregation, and fluxional behavior. While [AlMe2](+) is the primary product of the metalation, [AlMe](2+) is utilized to alleviate overcrowding or to aid aggregation. At the later stages of metalation, [AlMe2](+) groups start to scramble around congested sites. The ligands proved to be very robust and extremely flexible, offering a unique platform to study complex multinuclear metal arrangements.