Synthesis and X-ray structure of a phosphaferrocenium

Reaction of 1-chloro-2,3,4,5-tetraethylphosphole with lithium yields the tetraethylphospholyl anion which is homocoupled to form the 1,1′-bis-(tetraethylphosphole) upon reaction with iodine. The thermal reaction of this bis-(tetraethylphosphole) with the [FeCp*(CO)2]2 dimer (Cp*=C5Me5) affords the pentamethylcyclopentadienyl-tetraethylphosphaferrocene. Reaction of this phosphaferrocene with elemental iodine in dichloromethane at room temperature affords the corresponding pentamethylcyclopentadienyl-tetraethylphosphaferrocenium [Fe(Cp*)(C12H20P)][I3] complex which was structurally characterized. The complex adopts a full-eclipsed geometry. As usually observed in classical ferrocenes, oxidation of the Fe center to +3 oxidation state results in a lengthening of the centroid-Fe bond distances.