Azadiphosphaindane‐1, 3‐diyls: A Class of Resonance‐Stabilized Biradicals. Issue 3 (19th November 2020)

• Record Type: Journal Article
• Authors: Bresien, Jonas; Michalik, Dirk; Schulz, Axel; Villinger, Alexander; Zander, Edgar
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 3(2021)
• Page Start: 1507
• Page End: 1512
• Publication Date: 2020-11-19
• Subjects: aromaticity -- biradicals -- heterocycles -- molecule activation -- phosphorus; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202011886
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: 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 C6 H4 (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 . Abstract : Only one very bulky substituent R is required to stabilize the first stable heteroindanediyls (see picture), which represent a group of resonance‐stabilized phosphorus‐centered biradicals. Different types of oligomers formed by self‐activation of the aromatic backbone were observed for smaller substituents.