[K{V4O4(μ‐O)4(μ‐O2CCH2tBu)4}][O2CCH2tBu] · 2 tBuCH2CO2H, a Potassium Complex of an “Inorganic Crown Ether”The reaction of VOCl3 with Ag/KO2CCH2tBu yields the title compound (characterized by crystal and molecular structure analyses), which is the first oligonuclear vanadium complex with monofunctional carboxylate containing Vv centres exclusively. The potassium ion is coordinated by two planes of O2;−: the four μ‐oxo bridges of the puckered V4(μ‐O)4 ring and the plane spanned by the eight oxygen functions of the bridging carboxylate ligands, from wich it protrudes only slightly.