A Computational Study on the Stability of Oxaphosphirane Rings towards Closed‐Shell Valence Isomerization

• Published in: European Journal of Inorganic Chemistry
• Main Authors: Espinosa Ferao, Arturo, Streubel, Rainer
• Other Authors: Deutsche Forschungsgemeinschaft
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1002/ejic.201700177; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fejic.201700177; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ejic.201700177; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ejic.201700177

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.