The compounds Cp(2)Ln[N(QPPh(2))(2)] (Ln = La (1), Gd (2), Er (3), or Yb (4) for Q = Se, Ln = Yb (5) for Q = S) have been synthesized from the corresponding rare-earth tris(cyclopentadienyl) compound and HCN(QPPh2)2]. The structures of compounds 1, 2, 3, and 5, as determined by X-ray crystallography, consist of a Cp(2)Ln fragment, coordinated eta(3) through two chalcogen atoms and an N atom of the imidodiphosphinochalcogenido ligand [N(QPPh(2))(2)](-). In compound 4, the Cp2Yb moiety is coordinated eta(2) through the two Se atoms of the [N(SePPh2)(2)](-) ligand. P-31 and Se-77 (for 1) NMR spectroscopies fend insight into the solution nature of these species. Crystal data: 1, C34H30LaNP2Se2, triclinic, , a = 9.7959(10) Angstrom, b = 12.4134(13) Angstrom, 13.9077(14) Angstrom, alpha = 88.106(2)degrees, beta = 88.327(2)degrees, gamma = 68.481(2)degrees, V = 1572.2(3) Angstrom(3), T = 153 K, Z = 2, and R-1(F) = 0.0257 for the 5947 reflections with I > 2 sigma(I); 2, C34H30GdNP2Se2, triclinic, , a = 9.7130(14) Angstrom, b = 12.2659(17) Angstrom, c = 13.953(2) Angstrom, alpha = 88.062(2)degrees, beta = 87.613(2)degrees, gamma = 69.041(2)degrees, V = 1550.7(4) Angstrom(3), T = 153 K, Z = 2, and R-1(F) = 0.0323 for the 5064 reflections with I > 2 sigma(I); 3, C34H30ErNP2Se2, triclinic, , a = 9.704(2) Angstrom, b = 12222(3) Angstrom, c = 13.980(4) Angstrom, alpha = 88.230(4)degrees, beta = 87.487(4)degrees, gamma = 69.107(4)degrees, V = 1547.4(7) Angstrom(3), T = 152 K, Z = 2, and R-1(F) = 0.0278 for the 6377 reflections with I > 2 sigma(I); 4, C34H30NP2Se2Yb . C4H8O, triclinic, , a = 12.087(4) Angstrom, b = 12.429(4) Angstrom, c = 23.990(7) Angstrom, alpha = 89.406(5)degrees, beta = 86.368(5)degrees, gamma = 81.664(5)degrees, V = 3558.8(18) Angstrom(3), T = 153 K, Z = 4, and R-1(F) = 0.0321 for the 11 883 reflections with I < 2 sigma(I); and 5, C34H30NP2S2Yb, monoclinic, P2(1)/n, a = 13.8799(18) Angstrom, b = 12.6747(16) Angstrom, c = 17.180(2) Angstrom, beta = 91.102(3)degrees, V = 3021.8(7) Angstrom(3), T = 153 K, Z = 4, and R-1(F) = 0.0218 for the 6698 reflections with I > 2 sigma(I).