Reductive Reactivity of the Organolanthanide Hydrides, [(C₅Me₅)₂LnH]_<i>x</i>, Leads to <i>ansa</i>-Allyl Cyclopentadienyl (η⁵-C₅Me₄CH₂−C₅Me₄CH₂-η³)^2- and Trianionic Cyclooctatetraenyl (C₈H₇)^3- Ligands

The reductive reactivity of lanthanide hydride ligands in the [(C5Me5)2LnH]x complexes (Ln = Sm, La, Y) was examined to see if these hydride ligands would react like the actinide hydrides in [(C5Me5)2AnH2]2 (An = U, Th) and [(C5Me5)2UH]2. Each lanthanide hydride complex reduces PhSSPh to make [(C5Me5)2Ln(μ-SPh)]2 in ∼90% yield. [(C5Me5)2SmH]2 reduces phenazine and anthracene to make [(C5Me5)2Sm]2(μ-η3:η3-C12H8N2) and [(C5Me5)2Sm]2(μ-η3:η3-C10H14), respectively, but the analogous [(C5Me5)2LaH]x and [(C5Me5)2YH]2 reactions are more complicated. All three lanthanide hydrides reduce C8H8 to make (C5Me5)Ln(C8H8) and (C5Me5)3Ln, a reaction that constitutes another synthetic route to (C5Me5)3Ln complexes. In the reaction of [(C5Me5)2YH]2 with C8H8, two unusual byproducts are obtained. In benzene, a (C5Me5)Y[(η5-C5Me4CH2−C5Me4CH2-η3)] complex forms in which two (C5Me5)1- rings are linked to make a new type of ansa-allyl-cyclopentadienyl dianion that binds as a pentahapto−trihapto chelate. In cyclohexane, a (C5Me5)2Y(μ-η8:η1-C8H7)Y(C5Me5) complex forms in which a (C8H8)2- ring is metalated to form a bridging (C8H7)3- trianion.