Synthesis, characterization, and coordination chemistry of a phenanthridine-containing N-heterocyclic carbene ligand

An N-heterocyclic carbene ligand precursor bearing a pi-extended phenanthridine (3,4-benzoquinoline) unit is presented. The proligand was isolated as the imidazolium salt of chloride (1 center dot HCF6), bromide (1 center dot HBr), or hexafluorophosphate (1 center dot HPF6) counterions. These salts can be deprotonated and the carbene installed on silver centres using Ag2O as both a base and a source of metal ion. The resulting Ag(I) complex (1)AgCl can be used in a transmetalation reaction to generate a Pd(II) coordination complex (1)Pd(CH3CN)Cl-2. The characterization and photophysical properties of these complexes is presented, along with a demonstration of the utility of (1)Pd(CH3CN)Cl-2 in mediating a catalytic C-N cross-coupling reaction for the preparation of the pharmaceutical Piribedil.

Automated summary

A new N-heterocyclic carbene ligand precursor containing a pi-extended phenanthridine unit was presented. The precursor can be installed on silver centers and used in a transmetalation reaction to generate a Pd(II) coordination complex for catalyzing the synthesis of Piribedil.