Editing Organolithium reagent (section)

=== Nature of carbon–lithium bond ===
[[File:Allyllithium.svg|thumb|right|150x100px|Delocalized electron density in allyllithium reagents]] 
The relative [[electronegativity|electronegativities]] of carbon and lithium suggest that the C−Li bond will be highly polar.<ref name=gopakomar>
{{cite book| last1 = Jemmis | first1 = E.D.| last2 = Gopakumar | first2 = G. | chapter = Theoretical studies in organolithium chemistry| title = PATAI'S Chemistry of Functional Groups.| publisher = John Wiley & Sons, Ltd | year = 2009| isbn = 9780470682531 | doi = 10.1002/9780470682531.pat0297}}</ref><ref name=streiwieser>{{cite journal| title = Perspectives on Computational Organic Chemistry| author = Streiwieser, A.| journal = J. Org. Chem.| year = 2009| volume = 74| issue = 12| pages = 4433–4446| doi = 10.1021/jo900497s | pmid = 19518150| pmc = 2728082}}</ref><ref name=bickelhaupt>{{cite journal| title = Covalency in Highly Polar Bonds. Structure and Bonding of Methylalkalimetal Oligomers (CH3M)n (M = Li−Rb; n = 1, 4)| author = Bickelhaupt, F. M.| journal = J. Chem. Theory Comput.| year = 2006| volume = 2| issue = 4| pages = 965–980| doi = 10.1021/ct050333s | pmid = 26633056|display-authors=etal}}</ref>
However, certain organolithium compounds possess properties such as solubility in nonpolar solvents that complicate the issue.
<ref name="gopakomar"/> While most data suggest the C−Li bond to be essentially ionic, there has been debate as to how much [[covalent]] character exists in it.<ref name=streiwieser/><ref name=bickelhaupt/>  One estimate puts the percentage of ionic character of alkyllithium compounds at 80 to 88%.<ref>{{Cite journal|last=Weiss|first=Erwin|date=November 1993|title=Structures of Organo Alkali Metal Complexes and Related Compounds|journal=Angewandte Chemie International Edition in English|language=en|volume=32|issue=11|pages=1501–1523|doi=10.1002/anie.199315013|issn=0570-0833}}</ref>

In allyl lithium compounds, the lithium cation coordinates to the face of the carbon π bond in an η<sup>3</sup> fashion instead of a localized, carbanionic center, thus, allyllithiums are often less aggregated than alkyllithiums.<ref name=Reich /><ref name=Fraenkelallyllithium>
{{cite journal| title = Observation of a Partially Delocalized Allylic Lithium and the Dynamics of Its 1,3 Lithium Sigmatropic Shift| author = Fraenkel, G.|author2=Qiu, Fayang| journal = J. Am. Chem. Soc.| year = 1996| volume = 118| issue = 24| pages = 5828–5829| doi = 10.1021/ja960440j}}</ref> In aryllithium complexes, the lithium cation coordinates to a single carbanion center through a Li−C σ type bond.<ref name=Reich /><ref name=Fraenkel>
{{cite journal| title = The carbon-lithium bond in monomeric arllithium: Dynamics of exchange, relaxation and rotation| author = Fraenkel. G| journal = J. Am. Chem. Soc.| year = 1995| volume = 117| issue = 23| pages = 6300–6307| doi = 10.1021/ja00128a020 |display-authors=etal}}</ref>
{{multiple image| direction = vertical| width = 180 |height = 400| footer = Solid state structures of methyllithium tetramers, ''n-''butyllithium hexamers and polymeric ladder of phenyllithium| image1 = Methyllithium-tetramer-2-3D-balls.png| image2 = Butyllithium-hexamer-from-xtal-3D-balls-A.png| image3 = Phenyllithium-chain-from-xtal-Mercury-3D-balls.png}}