The Presence of Water in the Common CeCl3/RLi Alkylation System
journal contributionposted on 15.05.1996, 00:00 by William J. Evans, Jay D. Feldman, Joseph W. Ziller
Dehydration of CeCl3(H2O)7 following standard procedures for making the commonly-used CeCl3/RLi reagent forms a material containing water and not anhydrous CeCl3. Heating CeCl3(H2O)7 at 150 °C and 0.03 Torr for 12 h forms a material which has an elemental composition of [CeCl3(H2O)]n, contains water by Karl Fischer analysis, reacts with MeLi to form methane, and crystallizes from THF as [Ce(μ-Cl)3(THF)(H2O)]n in space group P1̄ with a = 6.691(2) Å, b = 7.433(2) Å, c = 10.092(2) Å, α = 84.46(2)°, β = 76.72(2)°, γ = 74.76(3)°, V = 471.0(2) Å3, ρcalcd = 2.37 g/cm3, and Z = 2 at T = 158 K. [Ce(μ-Cl)3(THF)(H2O)]n crystallizes in a layered structure in which eight-coordinate cerium atoms are ligated to terminal water and THF ligands and six bridging chlorides in a distorted square antiprismatic geometry. The THF ligands extend above and below the layers which contain the water molecules. Reactions of “CeCl3/RLi” must take into account the presence of 1 equiv of water.