Oxidations of N-coordinated Arsinidene and Stibinidene by Substituted Quinones: A Remarkable Follow-Up Reactivity.

The reactivity of pnictinidenes [2-(DippN=CH)-6-(DippNHCH 2 )C 6 H 3 ]E (where E=As (1) or Sb (2)) toward substituted ortho- and para-quinones is reported. The central pnictogen atom is easily oxidized by ortho-quinones closing five-membered EO 2 C 2 ring. The oxidized antimony derivatives are stable species, while in the case of arsenic compounds the hydrogen of the pendant amino NHCH 2 group cleaves one newly formed As-O bonds leading to the closure of a new azaarsole ring. Furthermore, a heating of these arsenic heterocycles resulted in a C-H bond activation at the NCH 2 group involved in this heterocycle followed by a reductive elimination of corresponding catechols and arsinidene [2,6-(DippN=CH)C 6 H 3 ]As. Using of para-quinones, resulted in the oxidation of the central atom with a concomitant hydrogen migration from NHCH 2 group even in the case of the antimony derivatives. The reductive elimination of hydroquinones is in this case feasible for all compounds. Studied compounds were characterized by multi-nuclear NMR, IR and Raman spectroscopy and single-crystal X-ray diffraction analysis. The theoretical study focusing the key compounds and reactions is also included.