Tetrameric zirconium(IV) complexes with bidentate ligands

Abstract

Oxozirconium(IV) chloride reacts with several heterocyclic bidentate ligands, 2,2'-bipyridyl (Bipy), 1,10-phenanthroline (Phen), 2-(2'-pyridyl) benzimidazole (PBH), 3,5-dimethyl-1 (2'-pyridyl) pyrazole (DMPP) and bidentate schiff bases obtained by condensing salicylaldehyde with aromatic amines, to form tetrameric complexes where the four zirconium atoms are connected in a ring by four pairs of hydroxy bridges. Each Zr atom has eight-coordinated dodecahedral structure as is the case with the parent compound ZrOCl₂. The compounds are formulated as [Zr₄(OH)₈(H₂O)₈(L)₄]X₈ (L=bidentate ligand) and [Zr₄(OH)₈(H₂O)₁₄(DMPP)]X₈ (X=Cl, NCS). The analytical data, conductance, IR, Raman and NMR spectra and the thermogravimetric measurements characterise the complexes. The thermogravimetric measurements show that the complexes lose H₂O followed by ligands finally forming ZrO₂ as the end product.