2,2′-Bipyridine

2,2′-Bipyridine is an organic compound with the formula. This colorless solid is an important isomer of the bipyridine family. It is a bidentate chelating ligand, forming complexes with many transition metals. Ruthenium and platinum complexes of bipy exhibit intense luminescence.

Preparation, structure, and general properties

2,2'-Bipyridine was first prepared by decarboxylation of divalent metal derivatives of pyridine-2-carboxylate:
It is prepared by the dehydrogenation of pyridine using Raney nickel:

Substituted 2,2'-bipyridines

Unsymmetrically substituted 2,2'-bipyridines can be prepared by cross coupling reaction of 2-pyridyl and substituted pyridyl reagents.

Structure

Although bipyridine is often drawn with its nitrogen atoms in cis conformation, the lowest energy conformation both in solid state and in solution is in fact coplanar, with nitrogen atoms in trans position. Monoprotonated bipyridine adopts a cis conformation.

Reactions

2,2'-bipyridine produces multiple coordination complexes. It binds metals as a ligand for chelation, forming a 5-membered chelate ring.