Metal complexes of backbone-halogenated imidazol-2-ylidenes.

In this manuscript, literature reports on mono- and di-halogen (F, Cl, Br, and I) substituted at positions 4 or/and 4,5 imidazol-2-ylidene (NHC) metal complexes are discussed: particularly, their structural diversity with various metals (groups 6-13), important physicochemical properties, catalytic and medicinal/biological applications are reviewed. To our knowledge, there are no literature reports on group 4 and 5 metal complexes with this type of NHC ligands. Halogenated imidazol-2-ylidene metal complexes deserve special attention because halogens are the classic electron donating groups (mesomerically) in conjugated aromatic/heteroaromatic ring systems, but electron withdrawing inductively.

Synthesis of 3-aryl-1-phosphinoimidazo[1,5-]pyridine ligands for use in Suzuki-Miyaura cross-coupling reactions.

3-Aryl-1-phosphinoimidazo[1,5-]pyridine ligands were synthesized from 2-aminomethylpyridine as the initial substrate two complementary routes. The first synthetic pathway underwent the coupling of 2-aminomethylpyridine with substituted benzoyl chlorides, followed by cyclization, iodination and palladium-catalyzed cross-coupling phosphination reactions sequence to give our phosphorus ligands. In the second route, 2-aminomethylpyridine was cyclized with aryl aldehydes, followed by the iodination and palladium-catalyzed cross-coupling phosphination reactions to yield our phosphorus ligands.

Synthesis of 3-aryl-2-phosphinoimidazo[1,2-]pyridine ligands for use in palladium-catalyzed cross-coupling reactions.

3-Aryl-2-phosphinoimidazo[1,2-]pyridine ligands were synthesized from 2-aminopyridine two complementary routes. The first synthetic route involves the copper-catalyzed iodine-mediated cyclizations of 2-aminopyridine with arylacetylenes followed by palladium-catalyzed cross-coupling reactions with phosphines. The second synthetic route requires the preparation of 2,3-diiodoimidazo[1,2-]pyridine or 2-iodo-3-bromoimidazo[1,2-]pyridine from 2-aminopyridine followed by palladium-catalyzed Suzuki/phosphination or a phosphination/Suzuki cross-coupling reactions sequence, respectively.