Zirconium and Hafnium Twin Monomers for Mixed Oxides

Abstract The synthesis of Zr and Hf twin monomers of type [M(2‐OCH 2 c C 4 H 3 O) 4 ( x HOCH 2 c C 4 H 3 O)] ( 3 , M=Zr, x =0; 4 , M=Hf, x =1) and M[(2‐OCH 2 ‐C 6 H 4 O) 2 (2‐HOCH 2 ‐C 6 H 4 OH)] ( 5 , M=Zr; 6 , M=Hf) by reacting M(OR) 4 (M=Zr, R= n C 3 H 7 , 1 ; M=Hf, R= n C 4 H 9 , 2 ) with 2‐furylmethanol or 2‐hydroxybenzyl alcohol is discussed. Complexes 3 – 6 were homopolymerized under acidic conditions. Additionally, 5 and 6 were copolymerized with 2,2′‐spirobi[4 H ‐1,3,2‐benzodioxasiline] (SBS). Under acidic conditions SBS forms a phenolic resin/SiO 2 nanostructured material. The resulting hybrid materials from the homopolymerization of 3 – 6 and the copolymerized materials from 5 and 6 were characterized by standard solid‐state analytics. The inorganic lattice of the MO 2 materials from the homopolymerized complexes 3 – 6 and SiO 2 /MO 2 from the copolymerization of 5 and 6 with SBS was obtained by air oxidation. The oxide materials were characterized by X‐ray powder diffraction (XRPD) and energy‐dispersive X‐ray analysis, which proved their identity. The inner surface area was determined by N 2 adsorption/desorption studies, which revealed surface areas of 100 m 2 g −1 for MO 2 . The mixed oxides SiO 2 /MO 2 were additionally investigated by differential scanning calorimetry and variable‐temperature XRPD to study the thermal behavior. It was found that crystallization of tetragonal MO 2 nanoparticles is characteristic within the SiO 2 matrix, but higher sintering temperatures caused crystallization of the SiO 2 lattice.