Editing Isolobal principle (section)

{{Short description|Method of predicting the bonding properties of certain organometallic compounds}}

In [[organometallic chemistry]], the '''isolobal principle''' (more formally known as the '''isolobal analogy''') is a strategy used to relate the structure of [[Organic compound|organic]] and [[Inorganic compound|inorganic]] molecular fragments in order to predict [[Chemical bond|bond]]ing properties of organometallic compounds.<ref name = Hoffmann>{{cite journal|last1=Hoffmann |first1=R.|author-link1 = Roald Hoffmann|journal=[[Angewandte Chemie International Edition|Angew. Chem. Int. Ed.]] |title=Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)|year=1982|volume=21|issue=10|pages=711–724|doi=10.1002/anie.198207113 |url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1981/hoffman-lecture.pdf}}</ref> [[Roald Hoffmann]] described molecular fragments as isolobal "if the number, [[Molecular symmetry|symmetry]] properties, approximate energy and shape of the [[frontier orbital]]s and the number of [[electron]]s in them are similar – not identical, but similar."<ref>In reference 10 of his Nobel Prize acceptance speech, Hoffmann states that the term "isolobal" was introduced in reference 1e, "{{cite journal|last1=Elian |first1=M. |last2=Chen |first2=M. M.-L. |last3=Mingos |first3=D. M. P. |author-link3=D. M. P. Mingos |last4=Hoffmann |first4=R. |journal=Inorg. Chem. |volume=15 |issue=5 |pages=1148–1155|date=1976 |doi=10.1021/ic50159a034 |title=Comparative bonding study of conical fragments}}", but that the ''concept is older''.</ref> One can predict the bonding and [[reactivity (chemistry)|reactivity]] of a lesser-known species from that of a better-known species if the two molecular fragments have similar frontier orbitals, the [[highest occupied molecular orbital]] (HOMO) and the [[lowest unoccupied molecular orbital]] (LUMO). Isolobal compounds are analogues to [[isoelectronic]] compounds that share the same number of [[valence electron]]s and structure. A graphic representation of isolobal structures, with the isolobal pairs connected through a double-headed arrow with half an orbital below, is found in Figure 1.

[[Image:Isolobal Figure1.png|thumb|600px|center|'''Figure 1:''' Basic example of the isolobal analogy]]

For his work on the isolobal analogy, Hoffmann was awarded the [[Nobel Prize in Chemistry]] in 1981, which he shared with [[Kenichi Fukui]].<ref>{{cite web|url = http://nobelprize.org/nobel_prizes/chemistry/laureates/1981/|title = The Nobel Prize in Chemistry 1981: Kenichi Fukui, Roald Hoffmann|access-date = December 22, 2010|publisher = [[Nobel Prize|nobelprize.org]]}}</ref> In his Nobel Prize lecture, Hoffmann stressed that the isolobal analogy is a useful, yet simple, model and thus is bound to fail in certain instances.<ref name = Hoffmann/>