The construction of transition metal co-ordination polymers is a well established facet of crystal engineering.1–4For several years, effort has been concentrated on the development of bridging ligands of ever-increasing sophistication to link metal centres and hence generate multi-dimensional, multi-functional architectures.1–5More recently the use of supramolecular synthons based on π–π stacking6and hydrogen-bonding7–10interactions has been developed, leading to a new era of network materials. The linking of transition metal cationic centres through anionsviahydrogen-bonded supramolecular synthons to fabricate new extended structures is a topic in which we are particularly interested as it brings together the complementary fields of hydrogen-bonded crystal engineering11,12and inorganic co-ordination polymer construction.1–5In a recent paper,8we reported the formation of a hydrogen-bonded rhombic (4,4) grid based on a combination of the bis(N-methylamidino-O-methylurea)copper(ii) cation, a planar four-fold connecting unit, with the chloride anion, [Cu(Lmm)2]·2Cl (MMCL). The four-fold connectivity of the cation arises from the presence of four pairs of N–H donors disposed at 90° intervals as shown inScheme 1. Two pairs of N–H donors are associated with non-co-ordinated nitrogen atoms (those hydrogen-bonded to X inScheme 1) while the other two pairs are associated with co-ordinated nitrogen atoms (those hydrogen-bonded to Y inScheme 1). The rhombic (4,4) grid results from the use of all four pairs of N–H donors to form hydrogen bonds to four symmetry-related chloride anions. The hydrogen-bonding assemblies linking cations and halide anions adopt R12(6) motifs as shown inScheme 1.Schematic representation of the [CuL2]2+cation showing the disposition of the four pairs of N–H donors and the formation of R12(6) motifs.A reassessment of earlier work13,14involving bis(amidino-O-ethylurea)copper(ii) cations and halide anions has revealed similar (4,4) grids. In the bromide, [Cu(LHe)2]·2Br (HEBR),13the cations are linked solely by halide anions as in [Cu(Lmm)2]·2Cl; in the chloride, [Cu(LHe)2]·2Cl·2H2O (HECL),14however, both halide anions and water molecules are involved in the hydrogen-bonding interactions.To investigate the prevalence of (4,4) grid formation we have synthesised and structurally characterised a range of compounds analogous to [Cu(Lmm)2]·2Cl and differing solely in alkyl substituents and anion. Thus, a total of ten compounds of diverse bis(N-alkylamidino-O-alkylurea)copper(ii) cations with chloride and bromide have been synthesised, of which six have been structurally characterised by single crystal X-ray diffraction methods. The cations are synthesised by solvolysis ofN-alkyl-2-cyanoguanidines, prepared by reaction of an alkylamine hydrochloride with sodium dicyanamide in butan-1-ol in the presence of a copper(ii) salt as shown inScheme 2. Consequently, by variation of alkylamine hydrochloride (MeNH2·HCl, EtNH2·HCl or PhCH2NH2·HCl), solvent (MeOH or EtOH) and copper(ii) salt (CuCl2·2H2O or CuBr2) a diverse range of complexes has been prepared.Synthetic route to the [CuL2]·2X hydrogen-bonded co-ordination complexes.