Synthesis and Reduction of Bimetallic Methyl-BridgedRare-Earth Metal Complexes (C5H4SiMe3)2Ln(μ-CH3)2 (Ln = Y TbDy)

摘要

The complexes [Cp′2Ln(μ-CH3)]2, (Cp′ = C5H4SiMe3; Ln = Y, Tb, Dy) were reduced to determine if these methyl-bridged complexes would form mixed valent 4fⁿ5d¹ Ln(II)/4fⁿ Ln(III) compounds or bimetallic 4fⁿ5d¹ Ln(II) compounds containing 5d¹–5d¹ metal–metal bonds upon reduction. Reaction of the known bridged-chloride complexes, [Cp′2Ln(μ-Cl)]2, >1-Ln (Ln = Y, Tb, Dy), with MeLi forms the bridged-methyl complexes [Cp′2Ln(μ-CH3)]2, >2-Ln, which were crystallographically characterized for Tb and Dy. KC8 reduction of >2-Ln in the presence of 2.2.2-cryptand produced >3-Y, >3-Tb, and >3-Dy, which exhibited intense dark colors and broad absorbance peaks around 400 nm with molar extinction coefficients of 1700, 2300, and 1800 M^–1 cm^–1, respectively, which are characteristics of Ln(II) ions. The dark maroon >3-Y product had an axial electron paramagnetic resonance spectrum at 77 K (g1 = 1.99, A1 = 17.9 G; g2 = 2.00, A2 = 17.7 G) and a two-line isotropic spectrum at 273 K (g = 1.99, A =18.4 G), which indicates that an Y(II) ion is present. Althoughthese results are indicative of Ln(II) ions present in the solution,crystallographic evidence was not obtained to establish the structureof these complexes.