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.

金属镱或钙与2当量的五苯基环戊二烯（pentaphenylcyclopentadiene，C5Ph5H）以及1当量的二苯基汞（HgPh2）在四氢呋喃（THF）中发生氧化还原转金属化配体交换反应，得到溶剂分离离子对（solvent-separated ion pairs，SSIPs）[M(THF)6][C5Ph5]2（M = Yb, Ca），该产物通过单晶X射线衍射分析得以表征。向分离得到的该类溶剂分离离子对中加入甲苯，可析出同配夹心配合物[M(C5Ph5)2]（M = Yb, Ca）。在金属钡与五苯基环戊二烯和二苯基汞的反应中，原位观测到了对应的溶剂分离离子对，仅能分离得到夹心配合物[Ba(C5Ph5)2]。对[M(C5Ph5)2]（M = Yb, Ba）开展单晶X射线衍射分析，证实了这类配合物具有两个平行环戊二烯配体的高对称结构。此外，还对二价镱配合物的氧化反应及金属-配体交换反应进行了研究。