The synthesis of the bulky divalent (polyphenylcyclopentadienyl)lanthanoid sandwich complexes [Ln(C₅Ph₅)₂] (Ln = Sm, Eu) and [Ln(C₅Ph₄H)₂(solv)] (Ln = Sm, solv = thf; Ln = Eu, solv = dme)], from redox-transmetalation/protolysis (RTP) reactions, has been achieved. An analogous reaction with Yb afforded the solvent-separated ion pair [Yb(dme)₄][C₅Ph₄H]₂. In addition, rare divalent samarium halide complexes [Sm(C₅Ph₅)(μ-Br)(thf)₂]₂ and [Sm(C₅Ph₄H)I(thf)₃], were also prepared, either by RTP or ligand rearrangement. X-ray studies showed that the [Ln(C₅Ph₅)₂] complexes adopt highly symmetrical sandwich structures, whereas the [Ln(C₅Ph₄H)₂(solv)] complexes have open sandwich structures. The unexpected, but limited, solubility of the [Ln(C₅Ph₅)₂] complexes allowed for variable-temperature NMR spectra of [Sm(C₅Ph₅)₂] to be obtained. Detailed 1D and 2D NMR studies were conducted on [Sm(C₅Ph₄H)₂(thf)] to ascertain its structure in donor and nondonor solvents. During the course of these studies, the mixed tetraarylcyclopentadienyl sandwich complex [Sm{C₅(2,5-Ph)₂(3,4-p-tol₂)H}₂(thf)] was also prepared in order to fully assign the spectrum of [Sm(C₅Ph₄H)₂(thf)]. The europium sandwich complexes [Eu(C₅Ph₅)₂] and [Eu(C₅Ph₄H)₂(dme)] exhibit remarkable luminescence properties with high quantum yields (45% and 41%, respectively) coupled w_ith long emission lifetimes (approximately 800 and 1300 ns, respectively) in toluene.