Résumé
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)(mu-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{C-5(2,5-Ph)(2)(3,4-p-tol(2))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)(3)(dme)] exhibit remarkable luminescence properties with high quantum yields (45% and 41%, respectively) coupled with long emission lifetimes (approximately 800 and 1300 ns, respectively) in toluene.