Carbodiphosphoranes (CDPs) are a family of divalent carbon ligands that are known for their exceptional electron donor properties. Herein, the preparation and reactivity of a family of three and four co-ordinate Fe carbodiphosphorane complexes is described. Hexaphenylcarbodiphosphorane (HCDP) [1] is shown to react with FeCl2(PPh3)2 to form the three coordinate adduct Fe(HCDP)Cl2 [2], which is equilibrium with its four coordinate dimer. Reaction of [2] with two equivalents of benzyl Grignard yields the corresponding dialkyl complex (HCDP)FeBn2 [3]. Combination of [2] with LiHMDS results in salt metathesis and the formation of the monosilylated derivative Fe(HCDP)Cl(N(SiMe3)2) [4]. Subsequent anion exchange leads to the three coordinate Fe(HCDP)(OTf)(N(SiMe3)2) [5] which was characterized crystallographically and in solution.
