Dipolar bond

A coordinate bond (also dative bond or donor - acceptor bond, the term " dative bond " is deprecated) is a technical term of complex chemistry. Such binding exists when the bonding electrons are in a binding electron pair, only one of the two binding partners. This refers to the molecule or ion as electron-deficient acceptor ( Lewis acid = ), one with the free electrons as donor ( = Lewis base ). In old textbooks this binding is partially still marked by an arrow in the direction of the acceptor. These representations are outdated. A coordinate bond is like any other covalent bond drawn as a line ( see, eg, adjacent sketch ).

A typical example is ammonia ( NH3), which provides its free electron pair on a coordinate bond available, see H3N - BF3 in the adjacent sketch. Formal thereby gives the nitrogen of an electron to the boron, which the former (generally: the donor) a formal positive, the latter (in general, the acceptor ) has received a formal negative charge. Note that these formal charges have nothing to do with the actual charge distribution: As nitrogen has a considerably higher electronegativity as Boron (3.0 versus 2.0 ) the bond to the nitrogen is out -polarized.