Project Details
Projekt
Organo-Ruthenium substituted Polyoxoanions and Their Homogeneous Oxidation Catalysis Properties
Applicant
Professor Ulrich Kortz, Ph.D.
Subject Area
Inorganic Molecular Chemistry - Synthesis and Characterisation
Term
from 2005 to 2010
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 14557360
We propose to synthesize novel and discrete polyoxotungstate molecules substituted by paramagnetic, redox-active transition metal centers. Our emphasis is on species where the incorporated transition metals are sterically accessible by having two or more terminal ligands. This will allow for orienting and binding of the organic substrate molecule, if possible in a regio- and stereoselective fashion. We are particularly interested in the synthesis of intrinsically chiral polyanions, an area which has not been worked on systematically to date. The synthetic strategy encompasses reaction of a transition metal precursor with the appropriate lacunary polyanion ligand. In this project we will focus on polyoxometalates with lone-pair containing hetero atoms (e.g. AsIII, SbIII). Regarding the multiple, redox-active transition metal centers we will study the group 8 elements Fe3+, Ru2+ and Os2+. To date only a handful of Fe3+ containing heteropolyanions with the above characteristics have been structurally characterized and the preliminary results of catalytic activity are highly promising. Interestingly, no structure of a lone pair containing heteropolyanion of Ru2+ or Os2+ has been reported to date. The structures of the novel compounds will be characterized by single-crystal X-ray diffraction, multinuclear NMR, electronic and vibrational spectroscopy. The catalytic activity of the novel polyoxometalates will be tested with the principal aim to design new, efficient oxidation systems employing environmentally friendly O2 or H2O2 as primary oxidants. These multi-metal clusters are attractive species because of their noticeable properties including high stability with respect to thermal and oxidative degradation, tunable solubility via counterion metathesis (from water to organic media and also perfluorohydrocarbons), nano-sized dimensions, gram-scale synthesis and photocatalytic activity. Our approach will focus on (i) catalyst screening using some benchmark oxidative transformations, (ii) reaction optimisation by evaluating catalyst loading, stability, and scope of the process (iii) mechanism investigation (iv) minimisation of the environmental impact in green/alternative solvents (e.g. water, fluorinated liquids), (v) use of alternative activation techniques including microwave irradiation (MW) and photoirradiation (hv). The proposed collaboration will bring together laboratories with complementary expertise on polyoxometalate engineering and synthesis, solid state and solution speciation, homogeneous and heterogeneous catalysis, mechanistic investigation and attention to environmental issues.
DFG Programme
Priority Programmes
