名称:
Synthesis, crystal structure, and chirality of divalent lanthanide reagents containing tri- and tetraglyme
摘要:
Six new divalent lanthanide complexes using triglyme (trigly) and tetraglyme (tetgly) as achiral ligands have been prepared, using a facile synthetic method, in search for enantioselective solid-state reagents. The crystal structures of cis-[SmI2(trigly)thfl] (1), trans[YbI2(trigly)thf] (2), trans-[SMI2(trigly)dme] (3), trans-[YbI2(tetgly)] (4), trans-[EuI2(tetgly)thfl] (5), and [SM(tetgly)2][SMI3(tetgly)]I (6) have been determined. All complexes, except 5, are chiral. The 10-coordinate cation in 6 displays a helical chirality since the two tetraglyme ligands are wrapped around the samarium ion. Since trans-[YbI2(tetgly)] (4), which has a chiral arrangement of terminal methyl groups, crystallizes as a conglomerate, preferential crystallization and consequent enantioselective reduction of acetophenone was attempted, but resulted in racemic products, possibly on account of racemic twinning in 4. (C) 2004 Elsevier B.V. All rights reserved.