An unprecedented mononuclear double helicate with a square planar metal ion

Abstract Reactions of the 1:2 condensate (L) of benzil dihydrazone and 1-methyl-2-imidazole carboxaldehyde with Cd(ClO 4 ) 2  ·  x H 2 O and CdI 2 yield [CdL 2 ](ClO 4 ) 2 ( 1 ) and LCdI 2 ( 2 ), respectively. The yellow ligand L, and its yellow complexes 1 and 2 are characterized by NMR and single crystal X-ray diffraction. Though L contains four N-donor centers, 1 is found to be a four-coordinate double helicate with a square planar Cd(II)N 4 core and 2 a spiral coordination polymer with tetrahedral Cd(II)N 2 I 2 moieties. The bidentate nature of L and the occurrence of the square planar coordination of Cd(II) is explained by DFT calculations.