Ga[OSi(OtBu)3]3·THF, a thermolytic molecular precursor for high surface area gallium-containing silica materials of controlled dispersion and stoichiometry. Issue 27 (17th June 2016)

• Record Type: Journal Article
• Authors: Dombrowski, James P.; Johnson, Gregory R.; Bell, Alexis T.; Tilley, T. Don
• Is Part Of: Dalton transactions. Volume 45:Issue 27(2016)
• Page Start: 11025
• Page End: 11034
• Publication Date: 2016-06-17
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt01676f
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Ga[OSi(O t Bu)3 ]3 ·THF was used as the first thermolytic single-source molecular precursor to generate gallium-containing silicas. Abstract : The molecular precursor tris[(tri- tert -butoxy)siloxy]gallium, as the tetrahydrofuran adduct Ga[OSi(O t Bu)3 ]3 ·THF (1 ), was synthesized via the salt metathesis reaction of gallium trichloride with NaOSi(O t Bu)3 . This complex serves as a model for isolated gallium in a silica framework. Complex1 decomposes thermally in hydrocarbon solvent, eliminating isobutylene, water, and tert -butanol to generate high surface area gallium-containing silica at low temperatures. When thermal decomposition was performed in the presence of P-123 Pluronic as a templating agent the generated material displayed uniform vermicular pores. Textural mesoporosity was evident in untemplated material. Co-thermolysis of1 with HOSi(O t Bu)3 in the presence of P-123 Pluronic led to materials with Ga : Si ratios ranging from 1 : 3 to 1 : 50, denotedUCB1-GaSi 3, UCB1-GaSi 10, UCB1-GaSi 20 andUCB1-GaSi 50 . After calcination at 500 °C these materials exhibited decreasing surface areas and broadening pore distributions with increasing silicon content, indicating a loss of template effects. The position and dispersion of the gallium inUCB1-GaSi materials was investigated using 71 Ga MAS-NMR, powder XRD, and STEM/EDS elemental mapping. The results indicate a high degree of gallium dispersion in all samples, with gallium oxide clusters or oligomers present at higher gallium content.