Stereo-Control in Zn(II) and Cd(II) Complexes of Tetraamines with Azacyclic Cores

Halide-dictated stereoselective formation of octahedral Δ-cis-α-[Zn(L)Cl2] or trigonal bipyramidal Λ-[Zn(L)I]I, where L is a chiral tetramine with a pyrrolidine or piperidine core, has been observed in both the solid state and in solution through a combination of SCXRD analysis, NMR spectroscopy, and theoretical calculations. Chameleonic behaviour is exhibited by the bromido compounds which form five- or six-coordinate complexes depending on the nature of the tetramine ligand. Only six-coordinate Δ-cis-α-[Cd(L)X2] complexes are observed for Cd(II), irrespective of L or X.