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Azadiphosphaindane‐1,3‐diyls: A Class of Resonance‐Stabilized Biradicals
Author(s) -
Bresien Jonas,
Michalik Dirk,
Schulz Axel,
Villinger Alexander,
Zander Edgar
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202011886
Subject(s) - benzene , steric effects , substituent , monomer , chemistry , ring (chemistry) , singlet state , derivative (finance) , resonance (particle physics) , aromaticity , stereochemistry , medicinal chemistry , crystallography , molecule , organic chemistry , excited state , polymer , physics , particle physics , nuclear physics , financial economics , economics
Conversion of 1,2‐bis(dichlorophosphino)benzene with sterically demanding primary amines led to the formation of 1,3‐dichloro‐2‐aza‐1,3‐diphosphaindanes of the type C 6 H 4 (μ‐PCl) 2 N‐R. Reduction yielded the corresponding 2‐aza‐1,3‐diphosphaindane‐1,3‐diyls ( 1 ), which can be described as phosphorus‐centered singlet biradical(oid)s. Their stability depends on the size of the substituent R: While derivatives with R=Dmp (2,6‐dimethylphenyl) or Ter (2,6‐dimesitylphenyl) underwent oligomerization, the derivative with very bulky R= tBu Bhp (2,6‐bis(benzhydryl)‐4‐tert‐butylphenyl) was stable with respect to oligomerization in its monomeric form. Oligomerization involved activation of the fused benzene ring by a second equivalent of the monomeric biradical and can be regarded as formal [2+2] (poly)addition reaction. Calculations indicate that the biradical character in 1 is comparable with literature‐known P‐centered biradicals. Ring‐current calculations show aromaticity within the entire ring system of 1 .