Reactivity of Ln(II) Complexes Supported by (C5H4Me)(1-) Ligands with THF and PhSiH3: Isolation of Ring-Opened, Bridging Alkoxyalkyl, Hydride, and Silyl Products

Reduction of Cp(3)(Me)Ln(THF), 1-Ln (Ln = La and Gd; Cp-Me = C5H4Me), with KC8 in the presence of 2.2.2-cryptand (crypt) generates dark solutions, 2-Ln, with EPR spectra consistent with Ln(II) complexes: an eight-line hyperfine pattern for La at g = 1.971 and a broad single line for Gd at g = 1.988. The solutions decompose within minutes, and in the La system, a decomposition product was isolated in which a molecule of THF had been reduced by two electrons and ring-opened to generate an alkoxyalkyl-bridged bimetallic La(III) complex, [K(crypt)](2)-[((Cp3La)-La-Me)(2)(mu-OCH2CH2CH2CH2)], 3-La. An analogous Pr complex, 3-Pr, was also crystallographically characterized. Since decomposition products were not readily isolated from the analogous yttrium (Cp3Y)-Y-Me(THF)/KC8/crypt reaction, the composition of the solution of 2-Y was probed by addition of the hydrogen delivery reagent, PhSiH3, which had previously been reported to form U(III) hydrides from tris(cyclopentadienyl) U(II) complexes. This generated an Y(III) silyl complex, [K(crypt)][(Cp3Y)-Y-Me(SiH2Ph)], 4, in addition to a hydride product, [K(crypt)][((Cp3Y)-Y-Me)(2)(mu-H)], 5. The retention of three Cp-Me ligands per metal in 3-Ln, 4, and 5 is consistent with the presence of a (Cp(3)(Me)Ln)(1-) species in 2-Ln.