Crystal structures of two deca-vanadates(V) with penta-aqua-manganese(II) pendant groups: (NMe4)2[V10O28{Mn(H2O)5}2]·5H2O and [NH3C(CH2OH)3]2[V10O28{Mn(H2O)5}2]·2H2O.

Two heterometallic deca-vanadate(V) compounds, bis-(tetra-methyl-ammonium) deca-aquadi-μ4-oxido-tetra-μ3-oxido-hexa-deca-μ2-oxido-hexa-oxidodimang-anese(II)-deca-vanadate(V) penta-hydrate, (Me4N)2[V10O28{Mn(H2O)5}2]·5H2O, A, and bis-{[tris-(hy-droxy-meth-yl)meth-yl]ammonium} deca-aquadi-μ4-oxido-tetra-μ3-oxido-hexa-deca-μ2-oxido-hexa-oxidodimanganese(II)deca-vanadate(V) dihydrate, [NH3C(CH2OH)3]2[V10O28{Mn(H2O)5}2]·2H2O, B, have been synthesized under mild reaction conditions in an aqueous medium. Both polyanions present two Mn(OH2)5 complex units bound to the deca-vanadate cluster through oxide bridges. In A, the deca-vanadate 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, tetra-methyl-ammonium and [tris-(hy-droxy-meth-yl)meth-yl]ammonium, respectively, and on the number and arrangement of the water mol-ecules of crystallization. In both compounds, the H atoms from the coordinating water mol-ecules participate in extensive three-dimensional hydrogen-bonding networks, which link the cluster units both directly and through solvent mol-ecules 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 inter-actions are also observed in both structures.