Reversible Formation and Transmetalation of Schiff-Base Complexes in Subcomponent Self-Assembly Reactions

Dinuclear complexes [Zn₂(NS,NS)₂] <b>3</b> and [Ni₂(NS,NS)₂] <b>6</b> bearing Schiff-base ligands featuring two NS donor groups were obtained in subcomponent self-assembly reactions using nickel or zinc as template metals. Several transmetalation reactions starting from <b>3</b> or <b>6</b> yielded the complexes [Pd₂(NS,NS)₂] <b>4</b> and [Co₂(NS,NS)₂] <b>5</b>, and their molecular structures were determined by X-ray diffraction. Starting from the mononuclear complex [Ni­(NS/NOH)₂] <b>9</b> featuring a coordinated NS Schiff base and a free NOH Schiff base, completely reversible thermodynamically controlled imine bond formation was observed leading to complex [Ni₂(NS,NS)₂] <b>6</b> and the free Schiff -base ligand NOH,NOH <b>10