B(C6 F5 )3 -Enabled Synthesis of a Cyclic cis-Arsaphosphene.

The synthesis and characterization of an (arsino)phosphaketene, As(PCO){[N(Dipp)](CH2 )}2 (Dipp=2,6-diisopropylphenyl) is reported along with its subsequent reactivity with B(C6 F5 )3 . When reacted in a stoichiometric ratio, B(C6 F5 )3 drove the insertion of the P=C bond of the phosphaketene into one of the As-N bonds of the arsino functionality, affording an acid-stabilized, seven-membered, cyclic arsaphosphene. In contrast, when catalytic amounts of B(C6 F5 )3 were employed, dimeric species, which formed through a formal [2+2] cycloaddition of the cyclic arsaphosphene, were generated. The cyclic arsaphosphene product represents the first example of such a compound in which the two substituents are arranged in a cis-configuration.