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Tris(cyclopentadienyl)cerium and -uranium: Relative basicity, structure, and reactions

Thesis/Dissertation ·
OSTI ID:6067303
The trivalent cerium complexes (RC{sub 5}H{sub 4}){sub 3}Ce{center dot}L have been prepared and structurally characterized in order to study the relative basicity of neutral donor ligands toward (RC{sub 5}H{sub 4}){sub 3}Ce. The relative order of increasing basicity is found to be PMe{sub 3} > pyr > P(OCH{sub 2}){sub 3}CEt > thf {approx} quin > PEt{sub 3} > P(OMe){sub 3} >>> NMe{sub 3}. The steric properties of the metal environment and the steric and electronic properties of the metal environment and the steric and electronic properties of the donor ligand influence complex stability. Solution equilibria measurements and crystallographic analyses support the postulate that M-L {pi}-bonding plays a role in (RC{sub 5}H{sub 4}){sub 3}U{center dot}L compounds and not in (RC{sub 5}H{sub 4}){sub 3}Ce{center dot}L compounds. The uranium metallocene, (MeC{sub 5}H{sub 4}){sub 3}U{center dot}thf, reacts with methyl-lithium at low temperature ({minus}30{degrees}C) in the presence of Me{sub 2}NCH{sub 2}CH{sub 2}NMe{sub 2} (tmed) to form a complex that contains a methyl group that is linearly and symmetrically bridging between two (MeC{sub 5}H{sub 4}){sub 3}U groups, and a MeC{sub 5}H{sub 4} group that is sandwiched between two Li(tmed) fragments.
Research Organization:
California Univ., Berkeley, CA (USA)
OSTI ID:
6067303
Country of Publication:
United States
Language:
English