The ability of the dinuclear Co-II complex [(L-Me)Co-2(II)(mu-Cl)](+) [1; (L-Me)(2-) = 3,6,9,17,20,23-hexamethyl-3,6,9,17,20,23-hexaaza-29,30-dithiol-13,27-di-tert-butyltricyclo[23.3.1(11.15)]triacont a-1(28), 11,13,15(30), 25,26-hexaene] to bind tetrahedral oxoanions of the transition metal has been investigated. Two new complexes, [(L-Me)Co-2(II)(mu-MoO4)] (2) and [(L-Me)Co-2(II)(mu-MoO3(OMe))](2)[Mo4O10(OMe)(6)] (3), were prepared by substitution reactions of 1 with (n-Bu4N)(2)-MoO4 in MeCN or with MoO3 center dot 2H(2)O/NEt3 in MeOH. Both compounds were characterized by X-ray crystallography. The dioctahedral complex 2 features a mu(1,3)-bridging MoO42- unit, whereas the cation in 3 hosts an unprecedented mu(1,3)-MoO3(OMe)(-) motif, demonstrating that four-coordinate molybdate esters can be stabilized in the binding pocket of the bowl-shaped [(L-Me)Co-2(II)](2+) complex. The results of IR, UV/vis, and cyclic voltammetry measurements are also reported.