Crystal engineering with short-chained amphiphiles: deca­sodium octa-n-butane­sulfonate di-μ-chlorido-bis­[di­chlorido­palladate(II)] tetra­hydrate, a layered inorganic–organic hybrid material

In the course of crystal-engineering experiments, crystals of the hydrated title salt, Na(10)[Pd(2)Cl(6)](C(4)H(9)SO(3))(8)·4H(2)O, were obtained from a water/2-propanol solution of sodium n-butane­sulfonate and sodium tetra­chlorido­palladate(II). In the crystal, sodium n-butane­sulfonate anions and water mol­ecules are arranged in an amphiphilic inverse bilayered cationic array represented by the formula {[Na(10)(C(4)H(9)SO(3))(8)(H(2)O)(4)](2+)}(n). Within this lamellar array: (i) a hydro­philic layer region parallel to the bc plane is established by the Na(+) cations, the H(2)O mol­ecules (as aqua ligands in κNa,κNa′-bridging coordination mode) and the O(3)S– groups of the sulfonate ions, and (ii) hydro­phobic regions are present containing all the n-butyl groups in an almost parallel orientation, with the chain direction approximately perpendicular to the aforementioned hydro­philic layer. Unexpectedly, the flat centrosymmetric [Pd(2)Cl(6)](2−) anion in the structure is placed between the butyl groups, within the hydro­phobic regions, but due to its appropriate length primarily bonded to the hydro­philic ‘inorganic’ layer regions above and below the hydro­phobic area via Pd—Cl(t)⋯Na- and Pd—Cl(t)⋯H—O(H)—Na-type (Cl(t) is terminal chloride) inter­actions. In addition to these hydrogen-bonding inter­actions, both aqua ligands are engaged in charge-supported S—O⋯H—O hydrogen bonds of a motif characterized by the D (4) (3)(9) graph-set descriptor within the hydro­philic region. The crystal structure of the title compound is the first reported for a metal n-butane­sulfonate.