Cuprous Tris(tert-butoxy)siloxy Complexes and Their Thermolytic Conversion to Copper-Silica and Copper Oxide-Silica Nanocomposites

摘要

The (tert-butoxy)siloxy complex [CuOSi(O~tBu)_3]_4 (1) was prepared by silanolysis of [CuO~t-Bu]_4 with (~tBuO)_3SiOH and examined as a single-source precursor to Cu/SiO_2 and Cu_nO/ SiO_2 (n = 1, 2) materials. The related complex {Cu[μ-OSiPh(O~tBu)_2]}_4 (4), obtained similarly, was characterized by X-ray crystallography as having a planar Cu_4O_4 core with oxygen-bridged Cu atoms. The highly associated, sublimable {NaCu[OSi(O~tBu)_3]_2}_6 (3) was obtained by the addition of NaOSi(O~tBu)_3 to 1 or by reaction of 2 equiv of NaOSi(O~tBu)_3 with CuCl. Thermogravimetric analysis (TGA) of 1 under both oxygen and argon reveals rather sharp, low-temperature conversions to the final ceramic compositions (onset temperatures: ca. 100℃ under oxygen; ca. 150℃ under argon). Under argon, the resulting material consists of Cu° and Cu_2O nanoparticles dispersed in silica, whereas an oxygen atmosphere leads to CuO nanoparticles in silica. These materials are carbon- and hydrogen-free and are produced by elimination of isobutene, tert-butyl alcohol, water, and silanol. The pyrolytic conversion of compound 4 occurs at higher temperature and more gradually but gives relatively clean conversion to a CuO/SiO_2 composite under an oxygen atmosphere. The volatility of 1 allows its use in CVD preparations of thin films. Amorphous thin films with a Cu/Si ratio of 1:0.85 (microprobe analysis) and thicknesses ranging from 200 nm to 6 μm have been obtained.