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A Computational Study on the Stability of Oxaphosphirane Rings towards Closed‐Shell Valence Isomerization
Author(s) -
Espinosa Ferao Arturo,
Streubel Rainer
Publication year - 2017
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201700177
Subject(s) - chemistry , heterolysis , bond cleavage , cleavage (geology) , isomerization , stereochemistry , crystallography , valence bond theory , exergonic reaction , medicinal chemistry , molecular orbital , catalysis , molecule , organic chemistry , geotechnical engineering , fracture (geology) , engineering
The stability of both unligated oxaphosphiranes 1 and their P ‐M(CO) 5 complexes 2 (M = Cr, W) has been explored with respect to their closed‐shell isomers, formed from either heterolytic C–O or P–C ring bond cleavage. C–O bond cleavage of 1 leads to valence isomers 3 featuring trigonal‐planar hybridization at P, whereas pyramidalized isomers 3′ are obtained for push–pull systems featuring electron‐donating substituents at C and electron‐withdrawing groups at P. Complexes 2 undergo C–O ring cleavage, affording side‐on complexes 4 , except for the unstable C , C ‐diamino‐substituted complex 2d , which yielded the end‐on complex 4′d . Most of the C–O bond‐cleavage processes are exergonic, but have moderately high energy barriers; C , C ‐difluoro‐substituted oxaphosphiranes were identified as thermodynamically stable. C–P bond‐cleavage pathways afford zwitterionic species 6 or 7 as a result of pericyclic 4π‐electron conrotatory processes and are always disfavoured, compared with C–O bond cleavages. The cases of 1n , u , v and 2e are noteworthy, as attempted C–P bond cleavage led to ring fragmentation to give carbonic acid difluoride and phosphinidene derivatives.