Coordination Behavior of Acetoacetate Ligands with Attached Methacrylate Groups Containing Alkyl-Spacers of Different Length to Titanium and Zirconium Alkoxides

Summary.

Metal-alkoxides containing polymerizable groups are regularly used as precursors for inorganic–organic hybrid materials applying the combination of the sol–gel process and organic polymerizations. Here we report the synthesis of acetoacetoxy derivatives that are linked to methacrylate groups via alkyl chains of different chain length. The coordination of the resulting molecules to titanium- and zirconium-alkoxides (M(OR)₄; M = Ti, Zr; R = ethyl, butyl, isopropyl) was investigated applying NMR and FT-IR measurements. The results were related to structural data of the dinuclear complex [Ti(Oⁱ Pr)₃(EAA)]₂ (HEAA: ethyl acetoacetate) which was obtained by single crystal X-ray diffraction. The study revealed that the β-keto ester groups acted as chelating ligands in all cases and thus polymerizable coordination compounds were formed. However, NMR analyses in solution showed that transesterification of the methacrylic-type monomers occurred even at mild conditions as a side reaction in a ratio which was found to be dependent on the type of metal alkoxide used.