Editing Coordinate covalent bond (section)

== Examples ==
[[File:NH3-BF3-adduct-bond-lengthening-2D.png|thumb|upright=1.25|Formation of an [[adduct]] of [[ammonia]] and [[boron trifluoride]], involving formation of a coordinate covalent bond.]]
Coordinate covalent bonding is ubiquitous.<ref>{{Greenwood&Earnshaw2nd}}</ref> In all [[metal aquo complex|metal aquo-complex]]es [M(H<sub>2</sub>O)<sub>''n''</sub>]''<sup>m</sup>''<sup>+</sup>, the bonding between water and the metal [[cation]] is described as a coordinate covalent bond.  Metal-ligand interactions in most [[organometallic]] [[Chemical compound|compounds]] and most [[coordination compound]]s are described similarly.

The term ''dipolar bond'' is used in [[organic chemistry]] for compounds such as [[amine oxide]]s for which the electronic structure can be described in terms of the basic [[amine]] donating two electrons to an oxygen atom.

:{{chem|R|3|N}} → O

The arrow → indicates that both electrons in the bond originate from the amine [[Moiety (chemistry)|moiety]]. In a standard covalent bond each atom contributes one electron. Therefore, an alternative description is that the amine gives away one electron to the oxygen atom, which is then used, with the remaining unpaired electron on the nitrogen atom, to form a standard covalent bond. The process of transferring the electron from nitrogen to oxygen creates [[formal charge]]s, so the electronic structure may also be depicted as

:{{chem|R|3|N|+|O|-}}

[[File:CoA6Cl3.svg|thumb|220px|Hexamminecobalt(III) chloride]]
This electronic structure has an [[electric dipole]], hence the name polar bond. In reality, the atoms carry [[partial charge]]s; the more [[electronegative]] atom of the two involved in the bond will usually carry a partial negative charge. One exception to this is [[carbon monoxide]]. In this case, the carbon atom carries the partial negative charge although it is less electronegative than oxygen.

An example of a dative covalent bond is provided by the interaction between a molecule of [[ammonia]], a [[Lewis base]] with a lone pair of electrons on the nitrogen atom, and [[boron trifluoride]], a [[Lewis acid]] by virtue of the boron atom having an incomplete [[octet rule|octet]] of electrons. In forming the adduct, the boron atom attains an octet configuration.

The electronic structure of a [[coordination complex]] can be described in terms of the set of [[ligand]]s each donating a pair of electrons to a metal centre.  For example, in [[hexamminecobalt(III) chloride]], each [[ammonia]] ligand donates its lone pair of electrons to the cobalt(III) ion. In this case, the bonds formed are described as coordinate bonds.  In the [[Covalent bond classification method|Covalent Bond Classification]] (CBC) method, ligands that form coordinate covalent bonds with a central atom are classed as L-type, while those that form normal covalent bonds are classed as X-type.