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.

A 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 as PowerPoint slide