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

作者：Espinosa Ferao Arturo; Streubel Rainer^*

来源：European Journal of Inorganic Chemistry, 2017, 2017(20): 2707-2712.

DOI：10.1002/ejic.201700177

• Oxaphosphirane
• Valence isomerization
• Ring-opening
• Density functional calculations

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 4 pi-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.

• 出版日期2017-5-26