Crystal structures of two deca­vanadates(V) with penta­aqua­manganese(II) pendant groups: (NMe(4))(2)[V(10)O(28){Mn(H(2)O)(5)}(2)]·5H(2)O and [NH(3)C(CH(2)OH)(3)](2)[V(10)O(28){Mn(H(2)O)(5)}(2)]·2H(2)O

Two heterometallic deca­vanadate(V) compounds, bis­(tetra­methyl­ammonium) deca­aquadi-μ(4)-oxido-tetra-μ(3)-oxido-hexa­deca-μ(2)-oxido-hexa­oxidodimang­anese(II)­deca­vanadate(V) penta­hydrate, (Me(4)N)(2)[V(10)O(28){Mn(H(2)O)(5)}(2)]·5H(2)O, A, and bis­{[tris­(hy­droxy­meth­yl)meth­yl]ammonium} deca­aquadi-μ(4)-oxido-tetra-μ(3)-oxido-hexa­deca-μ(2)-oxido-hexa­oxidodimanganese(II)deca­vanadate(V) dihydrate, [NH(3)C(CH(2)OH)(3)](2)[V(10)O(28){Mn(H(2)O)(5)}(2)]·2H(2)O, B, have been synthesized under mild reaction conditions in an aqueous medium. Both polyanions present two [Mn(OH(2))(5)](2+) complex units bound to the deca­vanadate cluster through oxide bridges. In A, the deca­vanadate unit has 2/m symmetry, whereas in B it has twofold symmetry. Apart from this, the main differences between A and B rest on the organic cations, tetra­methyl­ammonium and [tris­(hy­droxy­meth­yl)meth­yl]ammonium, respectively, and on the number and arrangement of the water mol­ecules of crystallization. In both compounds, the H atoms from the coordinating water mol­ecules participate in extensive three-dimensional hydrogen-bonding networks, which link the cluster units both directly and through solvent mol­ecules and, in B, through the ‘tris­’ cation hydroxyl groups. The cation in B also participates in N—H⋯O hydrogen bonds. A number of C—H⋯O inter­actions are also observed in both structures.