New base-free metallocenes of samarium and neodymium, an approach to stereoelectronic control in organolanthanide chemistry

New unsolvated metallocenes of early lanthanides, (Cp-4i)(2)Sm, COTSmCp4i, and COTNdCp4i (Cp-4i = (C5HPr4)-Pr-i) have been prepared and fully characterised, including X-ray structural analysis: the absence of ancillary base in these complexes is not only the consequence of steric effects; these results bring up the debated question of electronic control in organolanthanide chemistry.