Mixed-Valence Iron Complexes Containing End-On Bridging Cyaphide Ions

Iron cyanide compounds are among the oldest known synthetic coordination compounds, dating back to the early 18(th) century. By contrast, iron complexes of the cyaphide ion (C P-)-a heavy valence isoelectronic analog of the cyanide ion-are unknown. Herein we report the synthesis of highly stable mono- and bis-cyaphide complexes of iron(II), namely Fe(depe)(2)(Cl)(CP) and Fe(depe)(2)(CP)(2) (depe = 1,2-bis(diethylphosphino)ethane). These iron(II) cyaphide complexes are capable of further coordination to iron(I) in a hitherto unknown linear coordination geometry, affording the conjugated multimetallic mixed-valence complexes [{Fe(depe)(2)}(2)(mu-CP)(N-2)][BAr4F](2) and [{Fe(depe)(2)}(3)(mu-CP)(2)][OTf](2).