Site-isolated Pt-SBA15 materials from tris(tert-butoxy)siloxy complexes of Pt(II) and Pt(IV)

Abstract

Two novel tris(tert-butoxy)siloxy complexes of Pt(II) and Pt(IV) were prepared in high yields, (cod)Pt[OSi(OtBu)3]2(1; 87%; cod = 1,5-cyclooctadiene) and Me3Pt(tmeda)[OSi(OtBu)3] (2; 81%; tmeda = N,N,N′,N′- tetramethylethylenediamine). The structures of these compounds were determined by multinuclear NMR spectroscopy and by single-crystal X-ray analysis. The thermolytic chemistry of 1 and 2 in the solid state was studied by thermogravimetric analysis. The thermal decomposition of these complexes resulted in the formation of Pt metal, with the elimination of HOSi(OtBu)3. Precursors 1 and 2 react with the surface Si-OH groups of mesoporous SBA15 silica to generate surface-supported Pt centers. The coordination environments of the supported Pt centers in these new materials, termed Pt(II)SBA15 and Pt(IV)SBA15, were investigated using Fourier-transform infrared spectroscopy, X-ray absorption near-edge spectroscopy, and extended X-ray absorption fine structure analysis. These materials were also characterized using N2porosimetry, powder X-ray diffraction and transmission electron microscopy. Comparisons with the molecular precursors 1 and 2 revealed many similarities, and the results are indicative of isolated Pt(II) and Pt(IV) centers. In addition, isolated Pt centers proved to be robust in inert atmosphere to 150-200 °C, which is similar to the decomposition temperatures of 1 and 2. © 2008 American Chemical Society.