Organolanthanoids XX . The synthesis of YbCp₂Cl(THF)_0.5 (Cp = cyclopentadienyl; THF = tetrahydrofuran), YbCp₂X(THF) (X = Br or I), and (YbCp₂X)₂ (X = Cl, Br, or I) by oxidation of YbCp₂ with metal and organic halides

Reaction of YbCp₂(DME) (Cp = cyclopentadienyl; DME = 1,2-dimethoxyethane) with MCl₂ (M = Hg, Cd, Zn, Pb, Sn, Cu, Pd, or Co) or MCl (M = Ag, Cu or Tl) in tetrahydrofuran (THF) gives the metal M and YbCp₂Cl(THF)_0.5, generally in excellent yield, with small amounts of TlCp and CoCp₂ also detected from TlCl and CoCl₂ respectively. Similarly, YbCp₂X(THF) (X = Br or I) and YbCp₂Cl(DME)_0.5 have been prepared in good yields by analogous oxidation with suitable mercury(II) halides. However YbCp₂(DME) and FeCl₃ yield ferrocene. In simpler syntheses, YbCp₂X(THF)_n (X = Cl, n = 0.5; X = Br or I, n = 1) have been obtained by reactions of YbCp₂(DME) with C₂Cl₆ or (CH₂X)₂ (X = Br or I) in THF, and (YbCp₂X)₂ by analogous reactions of unsolvated YbCp₂ in petroleum ether. The X-ray crystal structure of YbCp₂I(THF) (monoclinic, P2₁/c, a = 8.147(1), b = 13.788(2), c = 14.149(3)Å, β = 105.56(1)°, Z = 4, R = 0.042, for 2324 observed data) shows the complex to be monomeric with formal eight coordination for ytterbium, and with a pseudo-tetrahedral array of the centroids of the Cp rings, oxygen, and iodine ( 2.565 Å, Yb-O 2.311(5)Å, Yb-I 2.9316(7)Å).