The instability of AE radical intermediates and AE-AE bonds for the heavy metals, as well as charge delocalisation, all currently frustrate efforts to isolate monovalent heavy AE radical complexes, thus an alternative approach may be needed to open up heavy AE(I) chemistry more rapidly. Lappert and Evans have demonstrated that tris-cyclopentadienyl rare earth (RE) complexes [RE(Cp R )3] (RE = Y, La Cp R = C5H4SiMe3, Cpʹ; C5H3(SiMe3)2-1,3, Cpʹʹ) can be reduced with alkali metal reagents in the presence of a sequestering agent, usually 18-crown-6