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.