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Published on: October 6, 2023
Synthesis and reduction of [(C5H4SiMe3)2Ln(μ-OR)]2 (Ln = La, Ce) complexes: structural effects of bridging alkoxides
Adrian N Brown1, Jack N Kelleher1, Alexander M Brown2
1Department of Chemistry, University of Rhode Island, Kingston, RI 02881, USA. danhuh@uri.edu.
Abstract:
Alcoholysis of Cp'3Ln (Ln = La, Ce; Cp' = C5H4SiMe3) generate high-yielding (72-97%) bimetallic LnIII complexes of [Cp'2Ln(μ-OR)]2 [R = Et, iPr, or C6H4-4-Bu]. Single-crystal X-ray diffraction of these complexes reveal unexpected decreases in Ln⋯Ln distances, increasing Cpcent-Ln-Cpcent angles, and increasing intermolecular C⋯C contacts with bulkier bridging alkoxides, in line with structural control driven by significant dispersion forces. 1H NMR spectroscopy of [Cp'2Ce(μ-OEt)]2 and [Cp'2Ce(μ-OiPr)]2 revealed significantly upfield resonances assigned as methylene and methine moieties of -43.74 and -70.85 ppm, respectively. 2D 1H DOSY NMR experiments of [Cp'2Ce(μ-OiPr)]2 in C6D6 supported a dimeric structure in solution, including in the presence of a Lewis base (i.e., THF). Reduction of [Cp'2La(μ-OiPr)]2 using KC8 in the presence of 2.2.2-cryptand at -78 °C generated a purple solution and X-band EPR spectroscopy revealed an eight-line hyperfine pattern indicative of a LaII species.
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