Dinitrogen can be reduced by photochemical activation of the Ln(3+) mixed-ligand tris-(cyclopentadienyl) rare-earth complexes (eta(5)-C5Me5)(3-x)(Cs5Me4H)(x)Ln (Ln = Y, Lu, Dy; x = 1, 2). [(C5Me4R)(2)Ln](2)(mu-eta(2):eta(2)-N-2) products (R = H, Me) are formed in reactions in which N-2 is reduced to (N=N)(2-) and (C5Me4H) is oxidized to (C5Me4H)(2). Density functional theory indicates that this unusual example of rare-earth photochemistry can be rationalized by absorptions involving the (eta(3)-C5Me4H)(-) ligands.