Amide-water hydrogen-bond motifs in alkali-metal/crown ether complexes of carbamoyldicyanomethanide, C(CONH2)(CN)(2)(-)

A series of complexes have been obtained from the crystallisation of M(cdm) (M = Na, K; cdm = carbamoyldicyanomethanide) with crown ethers from aqueous solution. The structures of these complexes display a range of hydrogen-bonding tape and sheet motifs incorporating both coordinated and lattice water molecules. Identical syntheses result in differing degrees of hydration, and consequently different packing, despite only minor changes in the nature of counter-cation. Complexes with 12-crown[4], [ Na(12c4)(2)](cdm) center dot 2H(2)O 1 and [ K( 12c4)(2)](cdm) center dot H2O 2, both contain metal/crown sandwich complexes between hydrogen- bonded sheets of composition {cdm.xH(2)O}(n) (x = 1 or 2, respectively). The incorporation of a slightly larger crown ether in the complex [ K(15c5)(2)]( cdm) center dot H2O 3 incorporates isolated hydrogen- bonded tapes of cdm center dot H2O} rather than sheets and has been obtained as two polymorphs. A serendipitous waterfree structure, [K(15c5)(2)](cdm)(cdmH) 4, contains a protonated cdm ligand incorporated into 2D sheets with the anionic cdm. The use of 18-crown[6] yields a complex in which the cdm ligand is coordinated to potassium through a nitrile arm, [K(18c6)(cdm)(H2O)](5). The individual complexes in the structure of 5 join together through a hydrogen- bonded tape that incorporates all available donor and acceptor groups of both the cdm and aqua ligands.