Related Experiment Video
Updated: Nov 9, 2025

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
Isolation of Neutral, Mono-, and Dicationic B2 P2 Rings by Diphosphorus Addition to a Boron-Boron Triple Bond
Tobias Brückner1,2, Felipe Fantuzzi1,2,3, Tom E Stennett1,2
1Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97070, Würzburg, Germany.
Abstract:
The NHC-stabilised diboryne (B2 (SIDep)2 ; SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B2 P2 heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B2 P2 rings, with their diradicaloid, planar-ring isomers lying close in energy.
More Related Videos
Related Concept Videos
Hydroboration-Oxidation of Alkenes
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Hybridization of Atomic Orbitals II
Hybridization of Atomic Orbitals I
Preparation of Alcohols via Addition Reactions
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.

