Oxidative Addition-Reductive Elimination Supported by a Ligand-Element Cooperation at the Arsinidene and Stibinidene...

The treatment of pnictinidenes [2-(RNHCH₂)-6-(RN=CH)C₆H₃]E (1As/Sb) (where E=As or Sb) with benzoyl peroxide provided compounds [2-(DippNCH₂)-6-(DippN=CH)C₆H₃]E(O₂CPh) (2As/Sb) as a result of two step procedure, i. e. oxidation of the pnictogen centre followed by the elimination of benzoic acid. The reaction between 1As and diphenyl disulfide proceeded in the same vein yielding thiophenol and [2-(DippNCH₂)-6-(DippN=CH)C₆H₃]As(SPh) (3As). Analogous reaction of 1Sb furnished a mixture of [2-(DippNHCH₂)-6-(DippN=CH)C₆H₃]Sb(SPh)₂ (3'Sb), [2-(DippNCH₂)-6-(DippN=CH)C₆H₃]Sb(SPh) (3Sb) and PhSH, while NMR studies proved the existence of a dynamic equilibrium between all three compounds in solution and removal of incipient PhSH was necessary for the isolation of 3Sb. Both 1As/Sb smoothly reacted with 2-nitrosotoluene leading to [2-(DippNCH₂)-6-(DippN=CH)C₆H₃]E(O-NH-2-Me-Ph) 4As/Sb and with 4-phenyl-1,2,4-triazoline-3,5-dione giving [2-(DippNCH₂)-6-(DippN=CH)C₆H₃]E[(N(CO)-NH(CO))N-Ph] 5As/Sb. All compounds were characterized by IR, Raman, NMR spectroscopy, and the molecular structures, except for 3As and 5Sb, were determined by single-crystal X-ray diffraction. Furthermore, we scrutinized the thermally induced reductive elimination of benzoic acid and thiophenol from 2-3As/Sb, respectively, and that of 4-phenylurazole from 5As. These eliminations involve C-H activation at the CH₂N group, and the recovery of the pnictinidene center in [2,6-(RN=CH)₂C₆H₃]E (6As/Sb). Using DFT calculations a plausible mechanism was suggested for all the investigated reactions, which are in good agreement with the experimental observations.