Replacement of N-heterocyclic carbenes by N-heterocyclic silylenes at a Pd(0) center: Experiment and theory

Via NMR-spectroscopy the relative reactivity of N-heterocyclic silylenes (NHSi) and carbenes (NHC) was studied. Reaction of sterically crowded bis-N-heterocyclic Pd(0) carbene complexes with free N-heterocyclic silylenes led to complete displacement of the N-heterocyclic carbene, which is unexpected knowing that usually a silylene is a weaker bound ligand compared to a carbene. High-level DFT calculations on a small model system and the experimentally used complexes confirm the experimental findings and indicate that steric interactions play an important role in the substitution reaction.

Graphical abstractAn unexpected replacement of N-heterocyclic carbenes by N-heterocyclic silylenes was observed by NMR at a Pd(0) complex. The reaction was studied by DFT calculations to elucidate the bonding properties of N-heterocyclic ligands and the role of the steric bulk of the N-substituent.Figure optionsDownload full-size imageDownload as PowerPoint slide