Di(tert-butyl)phosphate Complexes of Aluminum: Precursors to Aluminum Phosphate Xerogels and Thin Films

Reactions of HO(O)P(O t Bu) 2 with Al 2 Me 6 and [Al(O i Pr) 3 ] 4 gave the new molecular aluminum phosphate complexes [Me 2 AlO 2 P(O t Bu) 2 ] 2 ( 1 ) and [Al(O i Pr) 2 O 2 P(O t Bu) 2 ] 4 ( 2 ), respectively. In the solid state, 1 exists as a centrosymmetric dimer consisting of two four-coordinate Al centers bridged by two phosphate groups. In the solid state 2 exists as a centrosymmetric tetramer in which the unique half of the tetramer consists of two aluminum atoms bridged by two di( tert -butyl)phosphate groups. The central part of the molecule contains a planar Al 2 O 2 four-membered ring containing two symmetry-related Al(1) atoms bridged by two −O i Pr ligands. Solution-phase thermolyses of 1 and 2 in organic solvents led to the formation of transparent and opaque xerogels, respectively, after air-drying. The xerogel derived from 1 in 2-propanol had a surface area of 442 m 2 g - 1 after calcination to 600 °C in air. Thin, transparent films of aluminum phosphate were prepared by chemical vapor deposition (CVD) using both 1 and 2 as molecular precursors.