Phosphaarsenes – Combining Phospha‐ and Arsa‐Wittig‐Reagents.

Dipnictenes of the type RPn=PnR (Pn=P, As, Sb, Bi) can be viewed as dimers of the corresponding pnictinidenes R−Pn. Phosphanylidene‐ and arsanylidenephosphoranes (R−Pn(PMe3); Pn=P, As) have been shown to be versatile synthetic surrogates for the delivery of pnictinidene fragments. We now report that thermal treatment of 1 : 1 mixtures of R−P(PMe3) and R’−As(PMe3) gives access to arsaphosphenes of the type RP=AsR’. Three examples are presented and the properties and reactivity of Mes*P=AsDipTer (<bold>1</bold>) (Mes*=2,4,6‐<italic>t</italic>Bu3‐C6H2; DipTer=2,6‐(2,6‐<italic>i</italic>Pr2C6H3)2‐C6H3) were studied in detail. Solid state 31P NMR spectroscopy revealed a large 31P NMR chemical shift anisotropy with a span of ca. 920 ppm for <bold>1</bold> while computational methods were employed to investigate this pronounced magnetic deshielding of the P atom in <bold>1</bold>. In the presence of the carbene IMe4 (IMe4=:C(MeNCMe)2) <bold>1</bold> is shown to be split into the corresponding NHC adducts Mes*P(IMe4) and DipTerAs(IMe4), which is additionally shown for diarsenes. [ABSTRACT FROM AUTHOR]