2,2′-Bipyridine (bipy or bpy, pronounced /ˈbɪpiː/) is an organic compound with the formula (C5H4N)2. 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:2
2C5H4NCOO− → (C5H4N)2 + 2CO2 + 2e−
It is prepared by the dehydrogenation of pyridine using Raney nickel:3
Submitted by W. H. F. Sasse1
2C5H5N → (C5H4N)2 + H2
Substituted 2,2'-bipyridines
Unsymmetrically substituted 2,2'-bipyridines can be prepared by cross coupling reaction of 2-pyridyl and substituted pyridyl reagents.4
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.5 Monoprotonated bipyridine adopts a cis conformation.6
Reactions
2,2'-bipyridine produces multiple coordination complexes. It binds metals as a chelating ligand, forming a 5-membered chelate ring.
See also
References
Broomhead J. A.; Young C. G. (1990). "Tris(2,2″-Bipyridine)Ruthenium(II) Dichloride Hexahydrate". Inorganic Syntheses. Vol. 28. pp. 338–340. doi:10.1002/9780470132593.ch86. ISBN 978-0-470-13259-3. 978-0-470-13259-3 ↩
Constable; Housecroft (2019). "The Early Years of 2,2'-Bipyridine—A Ligand in its Own Lifetime". Molecules. 24 (21): 3951. doi:10.3390/molecules24213951. PMC 6864536. PMID 31683694. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6864536 ↩
Sasse, W. H. F. (1966). "2,2′-Bipyridine". Organic Syntheses. 46: 5. doi:10.15227/orgsyn.046.0005. /wiki/Organic_Syntheses ↩
Liu, Tiandong; Fraser, Cassandra L. (2012). "Discussion Addendum for: Synthesis of 4-, 5-, and 6-Methyl-2,2'-bipyridine by a Negishi Cross-Coupling Strategy: 5-Methyl-2,2'-bipyridine". Organic Syntheses. 89: 76. doi:10.15227/orgsyn.089.0076. /wiki/Doi_(identifier) ↩
Merritt, L. L.; Schroeder, E. (1956). "The Crystal Structure of 2,2′-Bipyridine". Acta Crystallographica. 9 (10): 801–804. doi:10.1107/S0365110X56002175. https://doi.org/10.1107%2FS0365110X56002175 ↩
Göller, A.; Grummt, U.-W. (2000). "Torsional barriers in biphenyl, 2,2′-bipyridine and 2-phenylpyridine". Chemical Physics Letters. 321 (5–6): 399–405. Bibcode:2000CPL...321..399G. doi:10.1016/S0009-2614(00)00352-3. /wiki/Bibcode_(identifier) ↩