Synthesis and reaction of samarium(II) bis (trifluoromethanesulfonate) derived from metallic samarium and 1,5-dithioniabicyclo (3.3.0) octane bis(trifluoromethanesulfonate)

摘要

We report the first synthesis and characterization of salt-free samarium (II) bis (trifluoromethanesulfonate) complexes of the formula (Sm(OTf)_2(L)_(15)_n)(2a: L=MeCN; 2b:L =tert-BuCN; 3:L=THF). Complex 2a was prepared by oxidative reaction of metallic samarium with 1,5-dithioniabicyclo (3.3.0) octane bis (trifluoromethanesulfonate) (1) in acetonitrile. When a mixture of 1 and an excess of samarium metal in the presence of a catalytic amount of iodine in acetonitrile was stirred at 50 deg C for 24 h, the complex 2a was isolated as purple powder in 66 percent yield. Two-dimensional structure of 3 was elucidated by x-ray analysis. Addition of an excess acetonitrile to 3 regenerates 2a. we also demonstrate that the 2a mediates the intermolecular pinacol coupling reactions of aromatic ketones with high diastereoselectivity (up to 94:6 (dl: meso)) operated at -40 deg C in acetonitrile and at -78 deg C propionitrile.