Samarium complex is uniquely reactive

Abstract

Chemists at the University of California, Irvine, have discovered a way to insert two carbon monoxide molecules into a carbon-carbon double bond by the use of an organosamarium complex. The net reaction converts an alkene to a bis-enolate. William J. Evans, a chemistry professor at Irvine, and Donald K. Drummond, a graduate student, worked with the divalent organosamarium complex bis(pentamethylcyclopentadienyl) samarium(II) bis(tetrahydrofuranate) or [C 5 (CH 3 ) 5 ] 2 -Sm(THF) 2 [ J. Am. Chem. Soc. , 110 , 2772 (1988)]. The structure of this complex is somewhat analogous to that of ferrocene—in which two parallel cyclopentadienyl groups sandwich an iron cation—in that the aromatic pentamethylcyclopentadienyl groups sandwich the samarium cation. In the samarium complex, however, the pentamethylcyclopentadienyl groups are not parallel to each other. Rather, they are tilted, allowing the samarium to bind to the oxygen atoms on two tetrahydrofuran groups. Evans and coworkers have shown that this samarium co...