Transition metal catalysts can be used to promote the highly efficient synthesis of biologically active molecules. We have shown that Rh(I) and Ir(I) complexes containing N’N and N,P donor ligands are effective catalysts for key transformations in the synthesis of biologically active compounds. In particular, we have shown that bimetallic complexes of Ir(I) and/or Rh(I) can be significantly more efficient catalysts than their monometallic counterparts and that the two metal centres work cooperatively to promote both one and two step reactions.We have also made very significant improvements to the intermetallic cooperativity of the bimetallic systems using a novel series of complexes that are geometrically constrained. NMR spectroscopy was key to establishing an understanding of the molecular structure as well as the nature of the catalysis.
The covalent immobilisation of transition metal catalysts on solid supports offers the possibility of combining the significant advantages of homogeneous catalysis with the benefits of heterogeneous catalysts. We have immobilized our complexes on glassy carbon surfaces using robust C-C linkers, and the immobilized complexes achieved significantly higher turnover numbers than those of their homogeneous counterparts (Figure 1). Understanding the structure and mechanism of these new immobilised species is challenging, and solid state NMR can provide insight into the three dimensional structure of the supported complexes. Enhancement of NMR signals due to species involved in the catalytic cycle using para-Hydrogen enhancement is under investigation.