Reduction of Cp′ 3 ThCl, Cp′ 3 ThBr, and Cp′ 3 ThI (Cp′ = C 5 H 4 SiMe 3 ) with potassium graphite generates dark blue solutions with reactivity and spectroscopic properties consistent with the formation of Cp′ 3 Th. The EPR and UV-visible spectra of the solutions are similar to those of crystallographically-characterized tris(cyclopentadienyl) Th( iii ) complexes: [C 5 H 3 (SiMe 3 ) 2 ] 3 Th, (C 5 Me 4 H) 3 Th, (C 5 t Bu 2 H 3 ) 3 Th, and (C 5 Me 5 ) 3 Th. Density functional theory (DFT) analysis indicates that the UV-visible spectrum is consistent with Cp′ 3 Th and not [Cp′ 3 ThBr] 1− . Although single crystals of Cp′ 3 Th have not been isolated, the blue solution reacts with Me 3 SiCl, I 2 , and HCCPh to afford products expected from Cp′ 3 Th, namely, Cp′ 3 ThCl, Cp′ 3 ThI, and Cp′ 3 Th(CCPh), respectively. Reactions with MeI give mixtures of Cp′ 3 ThI and Cp′ 3 ThMe. Evidence for further reduction of the blue solutions to a Cp′-ligated Th( ii ) complex has not been observed. The crystal structures of Cp′ 3 ThMe and (Cp′ 3 Th) 2 (μ-O) were also determined as part of these studies.
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Electrochemical studies of tris(cyclopentadienyl)thorium and uranium complexes in the +2, +3, and +4 oxidation states
Electrochemical measurements on tris(cyclopentadienyl)thorium and uranium compounds in the +2, +3, and +4 oxidation states are reported with C 5 H 3 (SiMe 3 ) 2 , C 5 H 4 SiMe 3 , and C 5 Me 4 H ligands. The reduction potentials for both U and Th complexes trend with the electron donating abilities of the cyclopentadienyl ligand. Thorium complexes have more negative An( iii )/An( ii ) reduction potentials than the uranium analogs. Electrochemical measurements of isolated Th( ii ) complexes indicated that the Th( iii )/Th( ii ) couple was surprisingly similar to the Th( iv )/Th( iii ) couple in Cp′′-ligated complexes. This suggested that Th( ii ) complexes could be prepared from Th( iv ) precursors and this was demonstrated synthetically by isolation of directly from UV-visible spectroelectrochemical measurements and reactions of with elemental barium indicated that the thorium system undergoes sequential one electron transformations.
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- Award ID(s):
- 2102589
- NSF-PAR ID:
- 10335588
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 12
- Issue:
- 24
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 8501 to 8511
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1SC01906F
