Synthesis of N,O-heterocyclic carbene and coordination to rhodium(I) and copper(I)

5,7-Di-tert-butyl-3-phenyl benzoxazolium tetrafluoroborate 1 could be prepared by simple reaction of the corresponding aminophenol with triethyl orthoformate under acidic conditions. Both rhodium(I) and copper(I) complexes with benzoxazol-2-ylidene ligand were then efficiently synthesised in a straightforward and smooth manner involving the reaction of benzoxazolium salt 1 with metal precursor and an external base. The complexes have been fully characterised and used in metal-catalysed hydrosilylation of ketones, where they showed poor catalytic activity, presumably due to low stability of the complexes under those conditions.

Rhodium(I) and copper(I) complexes containing a N,O-heterocyclic carbene (NOHC) have been prepared and characterized by analytical techniques. The benzoxazolium salt, which is the precursor of the carbene ligand was efficiently obtained in two steps from the corresponding aminophenol.Figure optionsDownload as PowerPoint slide