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Selective functionalisation of the tridentate ligand 1-(2-aminoethyl)-3-methyl-3-(2-pyridyl)azetidine at its terminal amino-nitrogen atom can be readily achieved by both reductive alkylation and simple alkylation reactions to give tri-, quadri-, quinque- and sexi-dentate derivatives. Simple alkylation by 2-picolinyl chloride provides the only example of a second reaction pathway where the azetidine ring of the reactant has undergone activation towards ring opening. Structural characterisation of the Cu(ii) complexes of these ligands has revealed several remarkable aspects of their solid-state coordination chemistry, including the formation of infinite helical aggregates through π-stacking and tetramerisation through carboxylate bridging, as well as further examples of the crystallisation of mixed species found to be rather common with complexes of the parent ligand. [ABSTRACT FROM AUTHOR]

A relatively simple azetidine derivative with 2-aminoethyl and 2-pyridyl substituents functions as a tridentate ligand towards Cu(ii), giving species in which the CuN3unit is essentially planar and that, in the solid state, show a subtle balance between mononuclear and binuclear forms, allowing both to be simultaneously present in some lattices. Displacement of the ligand from Cu(ii) by the use of cyanide results in the formation of cyanogen, which appears to slowly react with the free amine to give an oxamidine characterised in its doubly-deprotonated form as its binuclear Ni(ii) complex. [ABSTRACT FROM AUTHOR]