Abstract:
During the past few years Curtis and coworkers House, D. A. & Curtis, N. F. (1964) J. Am. Chem. Soc. 86, 223 and references therein have synthesized a number of macrocyclic square planar Ni(II) complexes by the reaction of nickel amines with a variety of aliphatic aldehydes and ketones. The overall process involves a combination of a Schiff base reaction and an aldol-like condensation to produce a macrocyclic ligand system which contains four donor nitrogen atoms. The four nitrogen atoms co-ordinate to the metal ion in a square planar configuration to produce a complex metal cation.
Figure 1 shows the isomeric products formed by the reaction of tris ethylene diamine Ni(II) with acetone at room temperature. The complexes, which are present as their perchlorate salts, are diamagnetic and show ligand field transitions consistent with those predicted for square planar nickel (II) complexes. Infrared and chemical studies established the carbon skeletons of the ligands as shown. But although the two Diene compounds are chemically distinct and non-interconvertible, Curtis and coworkers could not establish which compound was the cis isomer and which was the trans isomer; hence the compounds were simply designated as A and B Dienes.
