The cyclopentadienylaluminum aryloxide derivatives bis(cyclopentadienyl)(2,6-di-tert-butyl-4-methylphenoxy)aluminum (1) and (eta(5)-cyclopentadienyl)bis(2,6-di-tert-butyl-4-methylphenoxy)aluminum (2) have been prepared via the alcoholysis of tricyclopentadienylaluminum with 2,6-di-tert-butyl-4-methylphenol. The X-ray crystal structure of 2 was determined. The molecule crystallizes in the monoclinic space group C2/c with a = 15.4870(6) Å, b = 11.5404(5) Å, c = 18.3294(7) Å, beta = 103.0990(10) degrees, Z = 4, and V = 3190.7(2) Å(3) (R[I > 2sigma(I)] = 0.0755, R(w) = 0.1489). In the solid state, the cyclopentadienyl ring is bound eta(5) to the aluminum atom. Ab initio calculations on model compounds indicate that the pentahapto geometry of the cyclopentadienyl ring is due to the electron-withdrawing nature of the aryloxide ligands which allows greater pi-interaction between the aluminum center and the cyclopentadienyl ligand.