Four-coordinate square-planar complexes based on [Zn(salen)] derivatives are conveniently captured inside a crystal matrix using a supramolecular protecting strategy (see figure). The four-coordinate species is accompanied by a five-coordinate complex that binds an axial ligand able to hydrogen bond to an N-heterocycle positioned in the axial region of the coordinative unsaturated derivative. The size of the N-heterocycle is a decisive stabilization parameter.
Trapping of a four-coordinate zinc salphen complex inside a crystal matrix
Chem. Eur. J. 2009, 15, 4233-4237.