Oxidations of N-coordinated Arsinidene and Stibinidene by Substituted Quinones - a Remarkable Follow-up Reactivity.

Abstract

The reactivity of pnictinidenes [2-(DippN=CH)-6-(DippNHCH2)C6H3]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 EO2C2 ring. The oxidized antimony derivatives are stable species, while in the case of arsenic compounds the hydrogen of the pendant amino NHCH2 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 NCH2 group involved in this heterocycle followed by a reductive elimination of corresponding catechols and arsinidene [2,6-(DippN=CH)C6H3]As. Using of para-quinones, resulted in the oxidation of the central atom with a concomitant hydrogen migration from NHCH2 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.