Atrane
Atranes are a class of tricyclic molecules with three five-membered rings. It is a heterocyclic structure similar to the propellanes. It has a transannular dative bond from a nitrogen at one bridgehead to a Lewis acidic atom such as silicon or boron at the other bridgehead.Voronkov, Mikhail G.; Baryshok, Viktor P. "Atranes - a new generation of biologically active substances" (in Russian) Vestnik Rossiiskoi Akademii Nauk 2010, volume 80, 985-992. The name "atrane" was first proposed by {{ill|Mikhail Grigorievich Voronkov|ru|Воронков, Михаил Григорьевич}}.
Nomenclature
Image:Allyl-silatrane-from-xtal-3D-balls.png of the allyl silatrane molecule]]
Various atranes are named depending on the central element, e.g. "silatrane" (E = silicon); "boratrane" (E = boron); "phosphatrane" (E = phosphorus), etc. It is also proposed that when Y = nitrogen, the prefix "aza" be inserted before element + "atrane" (azasilatrane, for example) because atranes wherein E = silicon and Y = oxygen have been referred to as just "silatranes".{{cite journal | doi = 10.1016/0010-8545(94)03007-D | title = Main group atranes: Chemical and structural features | year = 1994 | last1 = Verkade | first1 = John G. | journal = Coordination Chemistry Reviews | volume = 137 | pages = 233–295}}
Structure and properties
Silatranes exhibit unusual properties, as the transannular coordinate bond in atranes can be stretched (quasiatranes) and even broken (proatranes). The strength (and multiplicity) of the central bond depends on the stereoelectronic properties of the surrounding ligands, the electronegativity of the participating atoms, and the size of the rings. A strong driving force for the formation of the central bond is relief of ring strain from the otherwise-formed 8-membered rings.
Atranes exhibit biological activity in which the coordination of nitrogen to silane plays an important role. Some derivatives such as phenylsilatrane are highly toxic.
image:VerkadeProtn.svg gives an atrane.{{cite book|doi=10.1002/047084289X.rn00702.pub2|chapter=Proazaphosphatrane|title=Encyclopedia of Reagents for Organic Synthesis|year=2012|last1=Verkade|first1=John G.|last2=Urgaonkar|first2=Sameer|last3=Verkade|first3=John G.|last4=Urgaonkar|first4=Sameer|isbn=978-0471936237}}]]
Proazaphosphatrane is a very strong non-ionic base and is utilized in various types of organic synthesis as an efficient catalyst.