Effect of the Alkali-Metal Cation on the Bonding Mode of 2,5-Dimethylpyrrole in Divalent Samarium and Ytterbium Complexes

The reactions of SmI 2 (THF) 2 and YbI 2 (THF) 2 with the alkali-metal salts of 2,5-dimethylpyrrole, or the reaction of SmCl 3 (THF) 3 and YbCl 3 (THF) 3 with the same ligands followed by reduction with the appropriate alkali metals, led to the formation of divalent mono- and polynuclear complexes. Structural analysis of these complexes indicated that the bonding mode adopted by the ligand depends on the nature of the alkali-metal cation retained in the structure.