Kelly, Rory P., Bell, Toby D.M., Cox, Rosalind P., Daniels, Daisy P., Deacon, Glen B., Jaroschik, Florian, Junk, Peter C., Le Goff, Xavier F., Lemercier, Gilles, Martinez, Agathe, Wang, Jun, and Werner, Daniel (2015) Divalent tetra- and penta-phenylcyclopentadienyl europium and samarium sandwich and half-sandwich complexes: synthesis, characterization, and remarkable luminescence properties. Organometallics, 34 (23). pp. 5624-5636.

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Abstract

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 with long emission lifetimes (approximately 800 and 1300 ns, respectively) in toluene.

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