Zinc complexes of a tripodal ligand containing three different N-heterocyclic donor functions

The coordination chemistry of a chiral tripodal ligand L containing pyridyl, imidazolyl and pyrazolyl donor functions has been investigated in combination with zinc(II). While the reaction of a racemic mixture of L with ZnX2 (X = Cl, Br) leads to complexes LZnX2 with tetrahedrally coordinated zinc centres (the pyridyl donor function remains pending), the employment of Zn(ClO4)2 leads to the sandwich complex [L2Zn](ClO4)2 which due to the two possible configurations for L (S and R) occurs in form of two diastereomers (the meso form and the enantiomeric pair SS/RR). The crystal structures of all three compounds are discussed.

Graphical abstractA tripodal ligand containing pyridyl, imidazolyl and pyrazolyl donor functions has been employed in zinc chemistry. On employment of zinc halides 4-coordinate complexes are formed (see picture) while the replacement of the halides by weaker coordinating anions leads to 6-coordinated sandwich complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide