A series of trivalent lanthanide (Ln) benzenechalcogenolate (EPh, E = S,Se) complexes have been prepared and structurally characterized in an attempt to evaluate how metal size : chalcogen, and solvent influence structure and physical properties. The compounds [(py)(3)Ln(SPh)(3)](2) (Ln=Ho (1) and Tm (2)), [(py)(2)Sm(SPh)(3)](4) (3), [(THF)Sm(SPh)(3)](4n) (4), (THF)(3)Ln(SePh)(3)(Ln=Tm (5), Ho (6) : Er (7)), [(py)(3)Sm(SePh)(3)](2) (8), and [(THF)(4)Ln(3)-(SePh)(9)](n) (Ln=Pr (9), Nd (10), and Sm (11)) were isolated and characterized by IR, NMR, and UV-visible spectroscopy. Compounds 2-4, 7, S, and 10 have also been characterized by low-temperature single-crystal X-ray diffraction. Three trends in structure are clear. First, the tendency to form oligomeric structures is found to increase with the size of the lanthanide ion. Second, thiolates bridge metal ions to form polynuclear structures more effectively than selenolates. Finally, pyridine displaces bridging chalcogenolates to form less extended structures more effectively than THF. Compounds 5-7 are molecular fac-octahedral complexes, compounds 1, 2, and 8 are bimetallic molecules with a pair of chalcogen atoms spanning the pentagonal bipyramidal metal centers, compound 3 is a tetrametallic structure with an alternating (3-2-3) number of mu(2)-thiolates spanning the linear assembly of four seven-coordinate Sm(III) ions, and compounds 4, 9, 10, and 11 are polymers with sets of three doubly bridging benzenechalcogenolates connecting adjacent metal-ions, Resonance:Raman spectroscopy indicates that the intense electronic absorption associated with Sm(III) chalcogenolate is a chalcogen-to-metal charge-transfer excitation. Compounds 1 and 2 decompose thermally to give Ln(2)S(3).