Intercepting a Transient Phosphino‐Arsinidene

A phosphino‐arsinidene derived from a diazaphospholidine scaffold (Ar**NCH2)2PAs (where Ar**=2,6‐bis[(4‐tert‐butylphenyl)methyl]‐4‐methylphenyl) was generated in situ and trapped with a range of reagents. Metathesis reactions between (Ar**NCH2)2PCl and either [Na(18‐crown‐6)][AsCO] or [Na(dioxane)x][AsCO] are believed to afford an arsaketene, (Ar**NCH2)2PAsCO, which readily loses carbon monoxide under ambient conditions. The resulting transient arsinidene was shown to undergo cycloaddition reactions with excess AsCO−, but can be stabilised in the presence of Lewis bases. It displays contrasting reactivity from a previously reported phosphino‐phosphinidene. With isonitriles, rearrangements occur, however with PPh3 a phosphine‐stabilised arsinidene could be isolated and used for subsequent reactivity studies. This species was found to be a suitable starting material for a transition metal complex of the phosphino‐arsinidene, in which the P−As moiety coordinates side‐on to the metal centre. It′s a trap! We report the formation of a transient phosphino‐arsinidene and the result of trapping experiments with Lewis bases and a transition metal centre.