Choosing between Ti(ii) and Ti(iii): selective reduction of titanocene dichloride by elemental lanthanides

Abstract

The reduction of titanocene dichloride Cp₂TiCl₂ with lanthanide metals has led to the discovery of a surprising lanthanide effect: while with most lanthanides, a divalent [Cp₂Ti] equivalent was obtained, the use of samarium or ytterbium only led to the reduction to trivalent [Cp₂TiCl]-type complexes, including the structurally characterized heterobimetallic complex [Cp₂Ti(μ-Cl)₂SmCl₂(THF)₃]. These results were corroborated by reactivity studies (alkyne coupling and radical reactions), EPR spectroscopy and electrospray mass spectrometry, providing new insights into the reduction chemistry of lanthanide metals.