Highly Active Iron-NHC Complexes for Carbonyl Hydrosilylation
The catalytic hydrosilylation of carbonyl groups into alcohols is a powerful transformation in the laboratory and industry. Despite the recent advances in this field, the development of catalytic systems that can activate inexpensive silanes like polymethylhydrosiloxane (PMHS) under mild conditions at low catalyst loadings is still a challenge, especially with environmentally benign metals. In search of highly active iron catalysts, a series of iron complexes with the formulation FeL2 (L = bifunctional N,C-chelate ligands) was synthesized and their application towards the hydrosilylation of ketones is presented. In Chapter 2, through systematic modification of the stereo-electronic properties of the N-Heterocyclic carbene (NHC) backbone, an extremely active catalyst was found for the hydrosilylation of carbonyl groups with PMHS under mild conditions. In Chapter 3, a follow-up study on this highly active catalyst is presented; several modifications on the N-wingtip of the NHC portion of the ligand are made and the new complexes evaluated for catalysis. In Chapter 4, having identified a few highly active catalysts, we modified the third component of the ligand structure, the N-donor functionality. Different N-donor groups were successfully incorporated in the complex structure, and the catalytic activity of the new complexes was assessed. Finally, in Chapter 5, the catalytic mechanism was studied through different experiments, and a proposed mechanism based on the experimental findings is presented.
Catalysis, Homogeneous, Hydrosilylation, Iron, Ketones, NHC
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