The first use of tert-butylacetate as bridging ligand in 3d/4f-metal cluster chemistry, in conjunction with the versatile chelate ligand pyridine-2,6-dimethanol, has afforded a new family of [Cu(4)Ln(8)(OH)(6)(NO3)(2)(O2CCH2But)(16)(pdm)(4)] clusters with unprecedented structures and slow magnetization relaxation for the {Cu(4)(II)4Dy(8)(III)} member. The molecular structure of representative complex 1 consists of a {(Cu4Gd8III)-Gd-II} cage-like cluster built from two {CuGd3} cubanes which are linked to each other and to two {CuGd} subunits on opposite sides through two eta(2):eta(2):eta(2):mu(5) NO3- ions. The metal ions are additionally bridged by mu(3)-OH-, mu(3)-OR-, and mu-OR- groups to give an overall [Cu4Gd8(mu(5)-NO3)(2)(mu(3)-OH)(6)(mu(3)-OR)(2)(mu-OR)(8)](14+) core. Peripheral ligation about the core is provided by the N,O,O-chelating part of the pdm(2-) groups and, more impressively, by the oxygen atoms of 16 bridging (BuCH2CO2-)-C-t ligands; the latter are arranged into five classes, adopting a total of six different binding modes with the metal centers. The combined work demonstrates the ligating flexibility of tert-butylacetate ion and its usefulness in the synthesis of new 3d/4f-metal cluster compounds.