Reactive E=C(p‐p)π‐Systems. 55. [1] Ligand Properties of 1‐Trifluoromethyl‐2‐diethylamino‐2‐fluoro‐1‐arsaethene,F3CAs=C(F)NEt2

Due to the mesomeric interaction of the nitrogen lone pair with the As=C double bond, the perfluoroarsapropene derivative F₃CAs=C(F)NEt₂ ( 1 ) is sufficiently stable to serve as a ligand in transition metal carbonyl complexes. 1 was coordinated to chromium by reaction with the photochemically generated labile complex Cr(CO)₅(THF), yielding the monosubstituted pentacarbonyl derivative Cr(CO)₅F₃CAs=C(F)NEt₂] ( 2 ). Already at room temperature, this is slowly transformed into the binuclear complex F₃CAs=C(F)NEt₂]Cr(CO)₅]₂ ( 3 ) by replacing 1 from a neighbouring molecule by the stronger donor 2 . In a closed system 3 obviously exists in an equilibrium with 1 and 2 . Both complexes are related to the previously studied derivatives of the 2‐dimethylamino‐perfluoro‐1‐phosphapropene ligand. The products were identified by spectroscopic (IR, NMR) investigations and comparison with the related phosphaalkene complexes.