Synthesis and reduction of [(CHSiMe)Ln(μ-OR)] (Ln = La, Ce) complexes: structural effects of bridging alkoxides.

Alcoholysis of Cp'Ln (Ln = La, Ce; Cp' = CHSiMe) generate high-yielding (72-97%) bimetallic Ln complexes of [Cp'Ln(μ-OR)] [R = Et, Pr, or CH-4-Bu]. Single-crystal X-ray diffraction of these complexes reveal unexpected decreases in Ln⋯Ln distances, increasing Cp-Ln-Cp angles, and increasing intermolecular C⋯C contacts with bulkier bridging alkoxides, in line with structural control driven by significant dispersion forces. H NMR spectroscopy of [Cp'Ce(μ-OEt)] and [Cp'Ce(μ-OPr)] revealed significantly upfield resonances assigned as methylene and methine moieties of -43.74 and -70.85 ppm, respectively. 2D H DOSY NMR experiments of [Cp'Ce(μ-OPr)] in CD supported a dimeric structure in solution, including in the presence of a Lewis base (, THF). Reduction of [Cp'La(μ-OPr)] using KC 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 La species.