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

Abstract

In the course of crystal-engineering experiments, crystals of the hydrated title salt, Na10[Pd2Cl6](C4H9SO3)8·4H2O, 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 {[Na10(C4H9SO3)8(H2O)4]2+} n . Within this lamellar array: (i) a hydrophilic layer region parallel to the bc plane is established by the Na+ cations, the H2O molecules (as aqua ligands in κNa,κNa′-bridging coordination mode) and the O3S– 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 [Pd2Cl6]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—Clt...Na- and Pd—Clt...H—O(H)—Na-type (Clt 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.