Strategies for the Immobilization of Transition Metal Complexes on various Carrier Materials and their Catalytic Application

MCM-41 modified with B(C6F5)3 moieties was found to be a good carrier material on which to anchor the cationic [Cu(CH3CN)6]2+ and [Ce(CH3CN)6]3+ complexes. The heterogeneous catalyst MCM41-BCu shows relatively high product yields in olefin cyclopropanation at room temperature and remains active and stable for several catalytic runs. However, its selectivity is not as good as in case of the homogeneous [Cu(CH3CN)6][B(C6F5)4]2. In terms of selectivity MCM41-BCe is comparable to MCM41-BCu, however, in general the product yields of MCM41-BCe are much lower. At elevated temperatures the product yields of MCM41-BCe increase slowly. It seems recommendable to apply carrier materials with larger pore radii to avoid pore size dependent reaction hindrance. For both heterogeneous catalysts, no catalytic activity could be observed for isobutene polymerization.

It could be shown that the number of benzonitrile ligands (n = 5, 6) in transition metal complexes with the general formulae [M1(PhCN)6][B(C6F5)4]2 (M1 = Mn (1), Fe (2), Co (3)) and [M(PhCN)5][B(C6F5)4]2 (M2 = Ni (4), Cu (5), Zn (6)) strongly depends on the divalent transition metal cation. For compounds 1-3 an essentially octahedral environment is obtained, whereas pentasolvated benzonitrile divalent cations of the structure [M(PhCN)5]2+ are observed for compounds 4-6.

Novel organic-inorganic hybrid nanotubes, composed of alternating silica and ethane (EtSNT), ethylene (ESNT) or acetylene (ASNT) units, respectively, have been synthesized through coating of V3O7 fibers with bis(triethoxysilyl) ethane, -ethylene and -acetylene, and subsequent fiber template removal with HCl and H2O2. The compounds have been characterized by solid state NMR, FTIR, elemental analysis and TEM. TEM images show the hollow tubes and uncapped tube ends. The versatility of the new nanotubular materials has been demonstrated for the ESNT, which have been modified through reaction with bromine and subsequent grafting of the amino acid glycine, as a model compound for the immobilization of enzymes.

Novel organic-inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units, as well as brominated ESNT (Br-ESNT) and glycine modified Br-ESNT (Gly-ESNT) were characterized by IR and Raman spectroscopy. The results were compared with the spectral features of conventional silica nanotubes and amorphous silica. For all organosilica-nanotubes samples, characteristic "nanotube" vibrations were found. Furthermore, they exhibit characteristic signals, originating from the organic moieties, thus, the presence of the organic moieties in the frameworks could be proven. The IR spectrum of Br-ESNT exhibit very similar spectral features compared to the ESNT spectrum, but additional bands, assigned to C-Br stretching vibrations were observed. The presence of glycine in Gly-ESNT could be proven.