The presence of water in the common CeCl3/RLi alkylation system

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 degrees 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(mu-Cl)(3)(THF)(H2O)](n), in space group <P(1) over bar> with a = 6.691(2) Angstrom, b = 7.433(2) Angstrom, c = 10.092(2) Angstrom, alpha = 84.46(2)degrees, beta = 76.72(2)degrees, gamma = 74.76(3)degrees, V = 471.0(2) Angstrom(3), rho(calcd) = 2.37 g/cm(3), and Z = 2 at T = 158 K. [Ce(mu-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.