The compounds Y[N(QPPh(2))(2)](3) (Q = S (1), Se (2)) have been synthesized in good yield from the protonolysis. reactions between Y[N(SiMe3)(2)](3) and HN(QPPh(2))(2) in methylene chloride (CH2Cl2). The compounds are not isostructural. In 1, the Y atom is surrounded by three similar [N(SPPh2)(2)](-) ligands bound eta(3) through two S atoms and an N atom. The molecule possesses D-3 symmetry, as determined in the solid state by X-ray crystallography and in solution by Y-89 and P-31 NMR spectroscopies. In 2, the Y atom is surrounded again by three [N(SePPh2)(2)](-) ligands, but two are bound eta(2) through the two Se atoms and the other ligand is bound eta(3) through the two Se atoms and an N atom. Although a fluxional process is detected in the P-31 and Se-77 NMR spectra, a triplet is found in the Y-89 NMR spectrum of 2 (delta = 436 ppm relative to YCl3 in D2O, (2)J(Y-P) = 5 Hz). This implies that on average the conformation of one eta(3)- and two eta(2)-bound ligands is retained in solution. Crystallographic data for 1: C72H60N3P6S6Y, rhombohedral, c, a = 14.927(5) Angstrom, c = 56.047(13) Angstrom, V = 10815(6) Angstrom(3), T = 153 K, Z = 6, and R-1(F) = 0.042 for the 1451 reflections with I > 2 sigma(I). Crystallographic data for 2: C72H60N3P6Se6Y . CH2Cl2, monoclinic, P2(1)/n, a = 13.3511(17) Angstrom, b = 38.539(7) Angstrom, c = 14.108(2) Angstrom, beta = 94.085(13)degrees, V = 7241(2) Angstrom(3), T = 153 K, Z = 4, and R-1(F) = 0.037 for the 8868 reflections with I > 2 sigma(I).