Thomas Maschmeyer

Preparation, characterisation and performance of encapsulated copper-ruthenium bimetallic catalysts derived from molecular cluster carbonyl precursors

High-performance, bimetallic nanoparticle catalysts (M1+M2) were obtained by gentle thermolysis of their precursor metal-cluster carbonylates physisorbed inside the mesoporous channels of silica (the hexagons in the figure). The Cu–Ru catalyst anchored on silica is stable in use and has been tested in the catalytic hydrogenation of hex-1-ene, diphenylacetylene, phenylacetylene, stilbene, cis-cyclooctene, and D-limonene.

Constrained chiral catalysts

Some of the approaches previously used to perform reactions enantioselectively using heterogeneous catalysts, together with a few illustrative examples, are first briefly summarised. We then outline various advantages and opportunities that nowadays exist for the confinement of large and rather complicated chiral organometallic catalytic entities as well as reactant and product species inside the cavities of mesoporous silicas, the pore diameters of which fall in the range 25 to 100 A. The unique opportunities afforded by chiral chelate ligands based on bis-diphenyl-phosphinoferrocene (BPPFA) held within mesoporous silica are adumbrated. Examples of potentially useful reaction systems and general synthetic possibilities are discussed with the view to highlight the emerging potential of the mesoporous dimension in regio- and enantioselective catalysis.

Derivatised mesoporous solids

Abstract During the past twelve months the potential of derivatised mesoporous solids has been explored in many divergent areas of research. New synthetic routes in combination with the development and exploration of new concepts in the nanoscalar world have led to many significant discoveries.

Synthesis and characterisation by X-ray absorption spectroscopy of a suite of seven mesoporous catalysts containing metal ions in framework sites

MCM-41 type mesoporous silicas have been prepared in which one or more of the following elements are accommodated in framework sites: titanium, iron, chromium, vanadium, manganese, boron and aluminium. XRD and FTIR are used as aids to characterisation, which is achieved chiefly — and to a degree that arrives at valence states, bond lengths and coordination numbers of the metal ion — by X-ray absorption spectroscopy (XAS). Ti-containing MCM-41, as well as the Fe-, V- and Cr-containing variants, yield self-consistent, XAS-based, structural data of the respective metal-ion sites. Some of these (especially those containing Ti) are exceptionally good catalysts for the selective oxidation of large organic molecules such as limonene and norbornene.