Bis(1,1-dimethyl-guanidinium) tetra-aqua-dimethyl-tin(IV) bis-(sulfate).

Single crystals of the title salt, (C(3)H(10)N(3))(2)Sn(CH(3))(2)(H(2)O)(4)(2), formed concomitantly with the already known Sn(CH(3))(3)SO(4)·2H(2)O. In the title structure, the Sn(IV) atom displays a slightly distorted octa-hedral coordination geometry defined by four O water atoms in the equatorial positions and two methyl groups in the axial positions. In the crystal, various O-H⋯O and N-H⋯O hydrogen-bonding inter-actions between the organic cation and the coordinated water mol-ecules as donors and the sulfate O atoms as acceptors result in a three-dimensional structure. The Sn(IV) atom is located on an inversion centre, resulting in half of the complex metal cation being in the asymmetric unit.