Porous Silicate Materials Research Articles

Tris(oxalato) Complexes of Silicon as Precursors to Porous Silicate Materials: Synthesis and Structure

A series of alkylammonium tris(oxalato)silicate compounds [R{sub 4}N]{sub 2}[Si(C{sub 2}O{sub 4}){sub 3}], where R{sub 4}N{sup +} = (CH{sub 3}){sub 4}N{sup +} (1), (CH{sub 3}){sub 3}(C{sub 6}H{sub 5})N{sup +} (2), (CH{sub 3}CH{sub 2}){sub 4}N{sup +} (3), (CH{sub 3}CH{sub 2}CH{sub 2}){sub 4}N{sup +} (4), (CH{sub 3}(CH{sub 2}){sub 3}){sub 4}N{sup +} (5), and (CH{sub 3}(CH{sub 2}){sub 5}){sub 4}N{sup +} (6), were prepared as precursors to microporous materials. Compounds 1 and 2 were structurally characterized by X-ray crystallography. [(CH{sub 3}){sub 4}N]{sub 2}[Si(C{sub 2}O{sub 4}){sub 3}] and [(CH{sub 3}){sub 3}(C{sub 6}H{sub 5})N]{sub 2}[Si(C{sub 2}O{sub 4}){sub 3}] crystallize in the monoclinic P2{sub 1}/c and P2{sub 1}/n space groups respectively with a = 17.631(2) {Angstrom}, b = 10.1984(9) {Angstrom}, c = 12.095(1) {Angstrom}, {beta} = 108.810-(8){degrees}, and Z = 4 for 1 while a = 8.855(2) {Angstrom}, b = 18.050(2) {Angstrom}, c = 17.102(2) {Angstrom}, {beta} = 95.24(1){degrees}, and Z = 4 for 2. The oxalate (ox) ligands are arranged in an octahedral fashion around the silicon. Thermal decomposition of the oxalate complexes 1-6 results in amorphous silica. Single point determination of the surface area indicates a greater surface area is obtained as the size of the alkylammonium ions increases.