chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, a Verkade base (or Verkade superbase) is a superbase with the formula P(MeNCH₂CH₂)₃N. A colorless oil, it is an

aminophosphine In organophosphorus chemistry, an aminophosphine is a compound with the formula R3−nP(NR2)n where R = H or an organic substituent, and n = 0, 1, 2. At one extreme, the parent H2PNH2 is lightly studied and fragile, but at the other extreme tris(di ...

although its inventor John Verkade called it proazaphosphatrane. The trimethyl derivative or 2,5,8,9-tetraza-1-phosphabicyclo .3.3ndecane is the simplest. Diverse analogues of the Verkade base are known, e.g. with isopropyl groups in place of methyl.

Synthesis and reactions

The Verkade base is generated by the reaction of N,N,N-trimethyl

tren Tren may mean: * Tris(2-aminoethyl)amine, a coordination chemistry compound * Trenbolone, a veterinary steroid * ''Tren'', a 1978 Yugoslav film See also * train {{disambig ...

with

tris(dimethylamino)phosphine Tris(dimethylamino)phosphine is an organophosphorus compound with the formula P(NMe2)3 (Me = methyl). It is a colorless oil at room temperature, and is one of the most common aminophosphines. Its structure has been determined by X-ray crystallog ...

: :P(NMe₂)₃ + (MeNHCH₂CH₂)₃N → P(MeNCH₂CH₂)₃N + 3 Me₂NH The principal reaction of the Verkade base is protonation. The proton is attacked by the Verkade base at phosphorus, which induces the formation of a transannular P-N bond. The product exemplifies the structure of an

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 o ...

. 290 px, left, Protonation of Verkade base. The conjugate acid P(MeNCH₂CH₂)₃Nsup>+ has a pK_a of 32.9 in

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

. For comparison, the conjugate acid of triethylamine has a pK_a near 17 in acetonitrile. Owing to its ability to deprotonate weak carbon acids, the Verkade base catalyzes a variety of condensation reactions.

Related compounds

Phosphazenes are phosphorus(V) derivatives with the formula RN=P(NR₂)₃.

References

{{Organophosphorus Amides Organophosphanes Quaternary ammonium compounds Superbases Atranes