Monoclinic modification of bis-(μ(2)-pyridine-2,6-dicarboxyl-ato)-κO,N,O:O;κO:O,N,O-bis-[aqua-dibutyl-tin(IV)].

The Sn(IV) atom in the centrosymmetric dinuclear title compound, [Sn(2)(C(4)H(9))(4)(C(7)H(3)NO(4))(2)(H(2)O)(2)], exists in a trans-C(2)SnNO(4) penta-gonal-bipyramidal geometry. There are two half-mol-ecules in the asymmetric unit that are completed by inversion symmetry. The crystal studied was a non-merohedral twin with a ratio of 47.3 (1)% for the minor twin component. Bond dimensions are similar to those found in the tetra-gonal polymorph [Huber et al. (1989 ▶). Acta Cryst. C45, 51-54]. O-H⋯O hydrogen-bonding interactions stabilize the crystal packing.