A Multifunctional Substituted Cyclooctatetraene as a Ligand in Organosamarium Chemistry

The reactivity of the multifunctionalized cyclooctatetraene Li 2 (1,4-R 2 C 8 H 6 ) (R = o -(dimethylsilyl)- N,N -dimethylaniline) is reported. To obtain this ligand in large quantities, a new, safe, and convenient method for the preparation of cyclooctatetraene was developed. The ionic complex [Li(diglyme) 2 ][{1,4-R 2 C 8 H 6 } 2 Sm 2 ( μ -Cl) 3 ] was synthesized by the reaction of the ligand with SmCl 3 and characterized by single-crystal X-ray diffraction. The anion of the new complex is an unique example of a dimeric organolanthanide complex which is μ 2 -bridged by three chlorine atoms. In the solid state the donor functionality does not coordinate to the samarium center. As shown by spin lattice relaxation experiments, there is a coordination of one amino group to the samarium atom in solution. Density functional theory (DFT) calculations show that this coordination might in principle be in an intramolecular fashion. Reaction of Li 2 (1,4-R 2 C 8 H 6 ) with [(C 8 H 8 )SmI(THF) 2 ] does not lead to a mixed-sandwich complex. By a ligand rearrangement the nonfunctionalized complex [Li(THF) 3 { μ -( η 2: η 8 -C 8 H 8 )}Sm(C 8 H 8 )] was isolated and characterized by single-crystal X-ray diffraction analysis.