Reaction of [15]crown-5 with erbium nitrate and a range of nickel salts results in the formation of the hydrogen-bonded chain species [Er(NO3)3(H2O)3]. [15]crown-5 H2O (3), [Ni(H2O)6]Br2 [15]crown-5 2H2O (4), [Ni(H2O)6](ClO4)2 x [15]crown-5 2H2O (5), [Ni(H2O)6](NO3)2 [15]crown-5 2H2O (6) and [[Ni(H2O)4]2(muCl)2]Cl2 [15]crown-5 (7). Complexes 3-5 exhibit low symmetry structures with 2-4 unique crown ether molecules, whereas 6 and 7 are more symmetrical. The factors contributing to this behaviour are discussed within the wider context of [15]crown-5 structures in the Cambridge Structural Database.

New palladium(II) bis(N-heterocyclic carbene) (NHC) complexes have been prepared via metallomacrocyclic Ag I ligand transfer agents. Reaction of 1,4-bis(3-isopropylimidazolium)xylene (1a) hexafluorophosphate with Ag 2 O gives a Ag I macrocyclic NHC complex in which two silver ions are sandwiched between two dipodal ligands (2a). The NHC moieties adopt a cisoid conformation relative to one another. Upon transfer to palladium to give [{PdCl 2 (MeCN)} 2 (bis-NHC)] (3a) the NHC ligands in the complexes adopt a mixture of cisoid and transoid conformers in the solid state,

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