Accessing Decaphenylmetallocenes of Ytterbium, Calcium, and Barium by Desolvation of Solvent-Separated Ion Pairs: Overcoming Adverse Solubility Properties

The redox-transmetalation ligand-exchange reaction of ytterbium or calcium metal with 2 equiv of pentaphenylcyclopentadiene (C5Ph5H) and 1 equiv of HgPh2 in thf afforded the solvent-separated ion pairs (SSIPs) [M(thf)6][C5Ph5]2 (M = Yb, Ca), which were characterized by single-crystal X-ray analyses. Addition of toluene to the isolated SSIPs led to the precipitation of the homoleptic sandwich complexes [M(C5Ph5)2] (M = Yb, Ca). In the reaction of barium metal with C5Ph5H and HgPh2 the corresponding SSIP was observed in situ, and only the sandwich complex [Ba(C5Ph5)2] could be isolated. Single-crystal X-ray analyses were carried out for [M(C5Ph5)2] (M = Yb, Ba), which confirmed the highly symmetric structure of these complexes with two parallel cyclopentadienyl ligands. Oxidation and metal-ligand exchange reactions were investigated for the divalent ytterbium complexes.