The coordination of Sc(III) to the oxacalix[3]arene macrocycles has been investigated. Reaction of Sc(trifluoromethanesulfonate)(3) with p-tert-butyloxacalix[3]arene, 2, in the presence of triethylamine results in the formation of the neutral complex [Sc(2)L(2)(dmso)(2)]. 2dmso . acetone, 3, where L is the trianion of p-tert-butyloxacalix[3]arene. The colorless crystals of 3, chemical formula C41.5H60O8.5S2Sc, are monoclinic, space group P2(1)/n, with a = 15.938(6) Angstrom, b = 11.328(3) Angstrom, c = 25.075(7) Angstrom, beta = 94.62(1)degrees, and Z = 4; R refined to 0.112. The single-crystal X-ray structure of 3 indicates the complex is dimeric with two mu-aryloxo linkages. The macrocycle in 3 coordinates as a trianionic, eight electron donor to scandium through each of the aryloxide oxygens and one ether linkage. Variable temperature H-1 NMR studies provide evidence for a dynamic isomerization of 3 on the NMR time scale.