Synthesis and X‐ray crystal structures of hypervalent arsenic compounds bearing arsenic‐iron bonds

A hypervalent arsorane with an As–Fe bond [ 6 : Rf₂As*FeCp(CO)₂ (Rf: o‐C₆H₄C(CF₃)₂O‐)] was synthesized by the reaction of the arsoranide anion ( 4‐Et ₄N: Rf₂As*^‐Et₄N⁺) with CpFe(CO)₂I ( 5 ) in the presence of AgBF₄. Diastereomeric arsoranes { 7a and 7b : Rf₂As*Fe*Cp(CO)(PPh₃)} were prepared by irradiation of 6 with a tungsten lamp in the presence of triphenylphosphine. X‐ray crystallographic analysis of 6 and 7a showed that the apical As–O bond lengths of these compounds are slightly longer than the equatorial As–C bonds. It is concluded that an electron‐donating group at the equatorial position elongates the apical E–O bond by electron donation to the apical oxygens. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:42–47, 2000