Abstract Hydrothermal reactions between the bisphosphonic acid 6-amino-1-hydroxy-1,1-hexylidenebisphosphonic acid and divalent hydrated metal nitrates of cobalt, nickel or zinc, in 1:0.75 molar ratio, afforded 1:2 mononuclear dichelate products Co 1, Ni 2 and Zn 3. Similar reactions using manganese or cadmium gave the 1:2 dinuclear products Mn 4 and Cd 5 with chelate bridging as well as chelate terminal bisphosphonate ligands. In contrast to mononuclear 1 the reaction between 4-amino-1-hydroxy-1,1-butylidenebisphosphonic acid and hydrated cobalt(II) nitrate gave a dinuclear product 6. The single-crystal X-ray structures of compounds 1–6 are discussed. The C6 alkylammonium chains in dinuclear compounds 4 and 5 display interesting supramolecular structure directing effects which are different from those in related compounds with C4 alkylammonium chains.