Dinitrogen Reduction, Sulfur Reduction, and Isoprene Polymerization via Photochemical Activation of Trivalent Bis(cyclopentadienyl) Rare-Earth-Metal Allyl Complexes

Dinitrogen can be reduced by photochemical activation of the trivalent rare-earth-metal bis­(pentamethylcyclopentadienyl) allyl complexes (C₅Me₅)₂Ln­(η³-C₃H₄R) (Ln = Y, Lu; R = H, Me) to form the (NN)^2– complexes [(C₅Me₅)₂Ln]₂(μ-η²:η²-N₂). This demonstrates that productive organolanthanide photochemistry is not limited to complexes of the unusual (η³-C₅Me₄H)⁻ ligand in the heteroleptic complexes (C₅Me₅)₂(C₅Me₄H)­Ln and (C₅Me₅)­(C₅Me₄H)₂Ln. Photolytic activation of (C₅Me₅)₂Ln­(η³-C₃H₅) (Ln = Y, Lu) in the presence of isoprene provides a rare photopolymerization route to polyisoprene. Sulfur can also be reduced by photolysis of (C₅Me₅)₂Ln­(η³-C₃H₅) (Ln = Y, Lu) to generate the (S)^2– complexes, [(C₅Me₅)₂Ln]₂(μ-S), which have variable Ln–S–Ln angles depending on crystallization conditions.