Superbulky Cp ligands – CpBIG
Although chemistry with the superbulky ligand Ph5Cp was initiated many years ago, it has never been fully developed for two reasons:
- the ligands are extremely bulky. Synthesis of its simple ferrocene is not easily achieved.
- all Ph5Cp complexes are extremely insoluble on account of their rigidity and high symmetry.
In cooperation with the University of Cape Town (John Moss) we prepared alkylated ligands of the form (4-nBu-C6H4)5Cp which we coin CpBIG.
The chemistry of CpBIG is very different from usual Cp-chemistry. The CpBIG ligands in (CpBIG)2M metallocenes do not repel each other but instead show attraction!
This is due to an extensive network of non-classical C-H···C hydrogen bonds.
We are currently exploring this unique ligand in catalysis.
(Harder et al Angew. Chem. 2008)