Heterometallic CoIINiII3 Complex

Abstract

Heterometallic multinuclear complexes have great potential to exhibit unique chemical and physical properties based on the cooperation of different metal ions. However, most examples previously reported depend on one-step methods or are based only on 4d- or 5d-metal ions. Here, a new strategy toward an otherwise difficult arrangement of different 3d-metal ions has been achieved by kinetically controlled multistep sequence: site-selective redox switching and transmetalation. This strategy utilizes inequivalent metal sites and a redox-active metal ion. As a model study, I chose a trigonal-pyramid-shaped tetranuclear structure to generate inequivalent metal sites, cobalt(II) as a redox-active metal ion, and nickel(II) as a second metal ion, which is difficult to distinguish with cobalt by thermodynamic methods. The construction of heterometallic CoIINi 3 II complex was accomplished in four-step sequence: (1) complexation with CoII; (2) site-selective oxidation at one of the CoII sites; (3) site-selective transmetalation of the other CoII sites with NiII; (4) reduction of the CoIII site. Notably, the obtained heterometallic complex could not be synthesized directly from ligand, CoII, and NiII under thermodynamic control.