Synthesis and characterization of {(diene)Rh[μ-OSi(OtBu)3]}2, a precursor to silica-bound rhodium

Abstract

Reaction of [(diene)RhCl]₂ with 2 equiv of KOSi(O^tBu)₃ afforded {(diene)Rh[μ-OSi(O^tBu)₃]}₂, where diene = cod (1) and nbd (2). Multinuclear NMR studies reveal that 1 and 2 have a dimeric structure with bridging tris(tert-butoxy)siloxy ligands. These dimers are folded along the O⋯O axis. Complexes 1 and 2 reacted with PR₃ (R = Me, Ph) to give monomeric products, the formulae of which depend on the amount of PR₃ added ((diene)Rh[OSi(O^tBu)₃](PR₃) and Rh[OSi(O^tBu)₃](PMe₃)₃). The behavior of 1 towards water and methanol is discussed. Thermogravimetric analyses (TGAs) of 1 and 2 reveal rather sharp conversions to rhodium-containing materials. Thermolysis of 1 in toluene at 180 °C resulted in formation of a black precipitate, which contained rhodium nanoparticles with an average diameter of 22 nm, as determined by powder X-ray diffraction (PXRD), after calcination at 300 °C for 1 h.