Reversible C–C coupling in phenanthroline complexes of divalent samarium and thulium

The reaction of a series of organolanthanide fragments of samarium and thulium with phenanthroline is reported. All adducts couple in the 4-position of the phenanthroline ligand to yield the 4–4′ dimers when they crystallize. The analysis of the solution structure revealed a thermally reversible C–C coupling in all cases.