Sigma bond metathesis with pentamethylcyclopentadienyl ligands in sterically crowded (C5Me5)3M complexes.

To further explore the reactivity of the (C(5)Me(5))(-) ligand in the sterically crowded (C(5)Me(5))(3)M complexes, reactions with PhEEPh (E = S, Se, Te) have been examined. With M = La, Pr, Nd, Sm, and Y, PhSSPh reacts to form the expected reduction products, [(C(5)Me(5))(2)M(SPh)](2), but the major organic byproduct is not the sterically induced reduction product, (C(5)Me(5))(2). Instead, the sigma bond metathesis product, C(5)Me(5)SPh, is the major byproduct. In contrast, reactions with (C(5)Me(5))(3)Ce and (C(5)Me(5))(3)U gave a mixture of C(5)Me(5)SPh and (C(5)Me(5))(2) as byproducts. PhSSPh reactions with the lanthanide nitrile adducts, (C(5)Me(5))(3)Ln(NCCMe(3))(2) (Ln = La, Ce) and (C(5)Me(5))(3)Nd(NCCMe(3)), formed [(C(5)Me(5))(2)Ln(SPh)(NCCMe(3))](2) and only C(5)Me(5)SPh as the byproduct. PhSeSePh reactions paralleled the PhSSPh results, but reactions of PhTeTePh with (C(5)Me(5))(3)La, (C(5)Me(5))(3)Sm, and (C(5)Me(5))(3)La(NCCMe(3))(2) gave only (C(5)Me(5))(2) as a byproduct.