View source for 2,2'-Bipyridine

{{chembox
|   Name = 2,2&#39;-Bipyridine
|   ImageFile = Bipy-2D-skeletal.png
<!-- | ImageSize = 188px -->
|   ImageName = 2,2'-bipyridine
|   IUPACName = 2,2'-Bipyridine
|   OtherNames = Bipyridyl<br />Dipyridyl<br />Bipy<br />Bpy<br />Dipy
| Section1 = {{Chembox Identifiers
|   CASNo = 366-18-7
|   SMILES = C1(C2=CC=CC=N2)=NC=CC=C1
|   ChemSpiderID = 13867714
|   RTECS = DW1750000
  }}
| Section2 = {{Chembox Properties
|C=10|H=8|N=2
|   Density =
|   MeltingPt = 70-73 °C
|   BoilingPt = 273 °C
  }}
| Section3 = {{Chembox Structure
|   CrystalStruct =
|   Dipole = 0 [[Debye|D]]
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS =
|   MainHazards = toxic
|   FlashPt =
|   RPhrases = 25
|   SPhrases = 36/37-45
  }}
| Section8 = {{Chembox Related
|   OtherCpds = [[4,4'-Bipyridine]]<br/>[[Pyridine]]<br />[[Phenanthroline]]<br />[[Terpyridine]]<br />[[Biphenyl]]
  }}
}}

'''2,2'-Bipyridine''' is a [[organic compound]] with the formula (C<sub>10</sub>H<sub>8</sub>N<sub>2</sub>).  This colorless solid, commonly abbreviated bipy or bpy (pronounced "b-pee"), is an important [[isomer]] of the [[bipyridine]] family.  It is a [[bidentate]] [[Chelation|chelating]] [[ligand]], forming complexes with many [[transition metal]]s. [[Ruthenium]] complex and [[platinum]] complexes of bipy exhibit intense [[luminescence]], which may have practical applications.

==Preparation and general properties==
It is prepared by the [[dehydrogenation]] of [[pyridine]] using [[Raney nickel]]:<ref>{{OrgSynth | author = Sasse, W. H. F. | title = 2,2’-Bipyridine | collvol = 5 | collvolpages = 102 | year = 1973 | prep = cv5p0102}}</ref>

:[[File:Synthesis of 2,2'-bipy.png|300px]]

Although uncoordinated 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. Only in acidic solution bipyridine adopts a cis conformation.<ref>Göller, A.; Grummt, U.-W.; "Torsional barriers in biphenyl, 2,2'-bipyridine and 2-phenylpyridine", Chem. Phys. Lett. '''2000''', 321, 399-405.</ref> The related N-heterocyclic ligand [[phenanthroline]] does not have the same conformational flexibility and tends to bind metal ions more strongly.

Reflecting the popularity of this ligand design, many substituted variants of bipy have been described.<ref>{{OrgSynth | author = Smith, A. P.; Lamba, J. J. S.; Fraser, C. L. | title = Efficient Synthesis of Halomethyl-2,2'-Bipyridines: 4,4'-Bis(chloromethyl)-2,2'-Bipyridine | collvol = 10 | collvolpages = 107 | year = 2004 | prep = v78p0082}}</ref><ref>{{OrgSynth | author = Smith, A. P.; Savage, S. A.; Love, J.; Fraser, C. L. | title = Synthesis of 4-, 5-, and 6-Methyl-2,2'-Bipyridine by a Negishi Cross-Coupling Strategy | collvol = 10 | collvolpages = 517 | year = 2004 | prep = v78p0051}}</ref>

==Coordination chemistry==
===Illustrative complexes===
*Mo(CO)<sub>4</sub>(bipy), derived from [[molybdenum carbonyl|Mo(CO)<sub>6</sub>]].
*RuCl<sub>2</sub>(bipy)<sub>2</sub>,<ref>{{cite journal | author = Lay, P. A.; Sargeson, A. M.; [[Henry Taube|Taube, H.]] | title = cis-Bis(2,2’-Bipyridine-N,N’) Complexes of Ruthenium(III)/(II) and Osmium(III)/(II) | journal = [[Inorg. Synth.]] | year = 1986 | volume = 24 | pages = 291–299 | doi = 10.1002/9780470132555.ch78}}</ref> a useful precursor to mixed ligand complexes.
*[[Ruthenium tris(bipyridine) chloride|[Ru(bipy)<sub>3</sub>]Cl<sub>2</sub>]], a well known [[luminophore]].
*[Fe(bipy)<sub>3</sub>]<sup>2+</sup> is used for the [[colorimetry|colorimetric]] analysis of iron ions.

===Tris-bipy complexes===
Bipyridine complexes [[UV/VIS spectroscopy|absorb]] intensely in the visible part of the spectrum.  The electronic transitions are attributed to metal-to-ligand [[charge transfer complex|charge transfer]] (MLCT). In the "tris(bipy) complexes" three bipyridine molecules coordinate to a metal ion, written as [M(bipy)<sub>3</sub>]<sup>n+</sup> (M = metal ion; Cr, Fe, Co, Ru, Rh and so on; bipy = 2,2'-bipyridine).  These complexes have six-coordinated, [[octahedral molecular geometry|octahedral]] structures and two [[enantiomer]]s as follows:
:[[Image:Bpycomp.png|250px]]
[[Image:Fe-Bipy-3.png|thumb|right|Three dimensional view of the [Fe(bipy)<sub>3</sub>]<sup>2+</sup> complex.]]

These and other [[homoleptic]] tris-2,2'-bipy complexes of many transition [[metals]] are electroactive.  Often, both the [[metal]] centred and ligand centred electrochemical reactions are reversible one-[[electron]] reactions that can be observed by [[cyclic voltammetry]].  Under strongly reducing conditions, most tris(bipy) complexes can be reduced to neutral derivatives containing bipy<sup>-</sup> ligands.  Examples include M(bipy)<sub>3</sub>, where M = Al, Cr, Si.

==References==
<references/>

{{DEFAULTSORT:Bipyridine, 2,2'-}}
[[Category:Chelating agents]]
[[Category:Bipyridines]]

[[de:2,2′-Bipyridin]]
[[it:2,2'-bipiridina]]
[[nl:2,2'-bipyridine]]
[[pt:2,2'-bipiridina]]
[[fi:2,2'-Bipyridiini]]
[[zh:2,2'-联吡啶]]

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[[Category:2Fix]]