Pincer-Supported Perfluororhodacyclopentanes: High Nucleophilicity of the M-C F Bond.

Perfluororhodacyclopentane supported by PBP pincer ligand PBP-Rh ^III (CF ₂ ) ₄ (2) was prepared from PBP-Rh ^I -PPh ₃ (1) and tetrafluoroethylene (TFE). By scXRD analysis, it was revealed that the Rh-C ^F bond trans to the boryl ligand was largely elongated compared to the one in the apical position. Although M-C ^F bonds of perfluorometallacyclopentanes are known to be very stable, 2 shows high reactivity toward hydrogenolysis, iodinolysis and protonolysis, thanks to the strong trans-effect of the highly σ-donating boryl ligand. Analogous PCP pincer complex PCP-Rh ^III (CF ₂ ) ₄ (4) showed slower reaction rate both in oxidative cyclization with TFE and hydrogenolysis of Rh-C ^F bond. Catalytic production of 1,1,2,2,3,3,4,4-octafluorobutane from two TFE and hydrogen in one pot was achieved via repetitive oxidative cyclization of TFE and Rh followed by the hydrogenolysis of Rh-C ^F bonds. This report demonstrates the possible application of PBP-pincer skeleton to the preparation of fluorinated compounds from TFE.
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