Synthetic crystallography: synthon mimicry and tecton elaboration in metallate anion salts

The use of molecular tectons (building blocks) able to form cyano-based hydrogen bonded synthons (NH...NC) to synthesise a diverse range of crystal structures is described. Square planar dianionic metal complexes with 4 terminal cyano groups are shown to form salts with the dications [4,4'-H(2)bipy](2+) and [4,4'-H(2)bipip](2+) in which hydrogen bond networks of varying dimensionality are formed. The structures of new salts of these cations with [M(CN)(4)](2-), [M(SCN)(4)](2-), and [M(mnt)(2)](2-) (M = Pt, and in one case Pd) are reported and compared with those of analogous [MCl4](2-) and [M(dtox)(2)](2-) salts. The consequences of the stereochemical preference of the cyano group for linear CN...H hydrogen bonding and the prospects for the elaboration of cyano-functionalised tectons to afford chemical and structural diversity in the structures synthesised are discussed.