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

Abstract

An N-heterocyclic carbene ligand precursor bearing a π-extended phenanthridine (3,4-benzoquinoline) unit is presented. The proligand was isolated as the imidazolium salt of chloride (1•HCl), bromide (1•HBr) or hexafluorophosphate (1•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)Cl2. The characterization and photophysical properties of these complexes is presented, along with a demonstration of the utility of (1)Pd(CH3CN)Cl2 in mediating a catalytic C-N cross-coupling reaction for the preparation of the pharmaceutical Piribedil.

When is a pyridine not a pyridine? Benzannulated N-heterocyclic ligands in molecular materials chemistry

“…35 From 4-bromo/4-amino phenanthridines, we can then construct P^N 35 , N^N 36,37 , N^N^N 38,39 , N^N^O [40][41][42] , N^C^N 43 and N^N^P 44 proligands; C^N and 8 bpy-style (N^N) 2 biphenanthridine 45 proligands are available from (6-halo)phenanthridines. 46 Coordination complexes of these ligands can be used in the Ni-catalyzed direct alkylation of C-H bonds in azoles, 39 as well as to effect acceptorless dehydrogenative coupling reactions in which alcohols can be employed as electrophiles. 47 Ru complexes of phenanthridine-containing P^N ligands can be used in this way to prepare a host of N-heterocycles, 48 including luminescent 49 and donor-acceptor-donor/donor-acceptor-acceptor type pyrimidines.…”