Silicon/Nitrogen donor ligands for base-metal catalysed C-C bond formation

Name: Serhii Tretiakov
Institution: Utrecht University (UU)
Start Date: 1/6/2016 Return
Supervisors: Dr. Marc-Etienne Moret  

Cross-coupling reactions between organic electrophiles and appropriate organometallic or related species are widely employed for the formation of carbon-carbon bonds. Such reactions are mostly mediated by palladium. However, considering its low abundance, relatively high cost, competition for its use from automotive and electronics industry, environmental impact of its extraction and toxicity, mid- to long-term use of this metal in cross-coupling chemistry is restricted. These limitations stimulated development of an alternative chemistry based on more Earth-abundant metals.

Iron is a good candidate due to low toxicity, low cost and high natural abundance. Its use, however, is problematic due to availability of several spin states that may take part in a catalytic cycle. Neutral ligands employed to control properties of a metal center are more likely to dissociate from a high-spin iron, which will generate a different iron species and disrupt the catalysis. Therefore, a new family of ligands must be developed to counter such a process.

A solution is sought in anionic silanide ligands that are isoelectronic to phosphines and contain nitrogen substituents on a silicon atom, which should stabilize the negative charge. Sterical bulk on the nitrogen substituents is increased to prevent nucleophilic atack on silicon instead of transmetallation on iron center. With the silanide ligands at hand, we are currently exploring transmetallation of iron complexes with various organometallic nucleophiles including Grignard reagents.

A related project involves exploration of high-valent iron species which are stabilized by related ligands. These compounds may find application in sustainable biomimetic oxidation of natural substrates. Spectroscopic properties on the respective complexes are studied in collaboration with Dr. Shengfa Ye, Dr. Eckhard Bill and MSc. Maxime Tarrago (MPI CEC).