RESUMEN
En route to putative rare-earth-metal alkylidene complex Li[Lu(CH2SiMe3)2(CHSiMe3)], according to Schumann's original protocol, the reaction of YCl3 with LiCH2SiMe3 in a mixture of diethyl ether and n-pentane afforded a neosilyl ate complex of composition Li3Y(CH2SiMe3)6. Tetrametallic complex Li3Y(CH2SiMe3)6 shows an unprecedented structural motif in the solid state and was further characterized by heteronuclear 1H/13C/7Li/29Si/89Y, as well as VT NMR and DRIFT spectroscopies. Analysis of the thermolysis product via heteronuclear NMR spectroscopy and its reactivity towards benzophenone gave strong evidence for an alkylidene formation upon decomposition. Application of a similar protocol for the smallest rare-earth-metal scandium led to the isolation of ate complex [Li(thf)4][LiSc2(CH2SiMe3)8] as the preferred crystallized product. Here, the reaction of adduct ScCl3(thf)3 and LiCH2SiMe3 was performed in Et2O/n-hexane, in the absence of additional THF. The reaction of LaCl3(thf) with 3 equiv. of LiCH2SiMe3 in THF/Et2O at -40 °C yielded the ate complex [Li(thf)4][La(CH2SiMe3)4(thf)], which is the first of its kind.
RESUMEN
CeCl3 (thf) reacts at low temperatures with MeLi, t-BuLi, and n-BuLi to isolable organocerium complexes. Solvent-dependent extensive n-BuLi dissociation is revealed by 7 Li NMR spectroscopy, suggesting "Ce(n-Bu)3 (thf)x " or solvent-separated ion pairs like "[Li(thf)4 ][Ce(n-Bu)4 (thf)y ]" as the dominant species of the Imamoto reagent. The stability of complexes Li3 Ln(n-Bu)6 (thf)4 increases markedly with decreasing LnIII size. Closer inspection of the solution behavior of crystalline Li3 Lu(n-Bu)6 (thf)4 and mixtures of LuCl3 (thf)2 /n-BuLi in THF indicates occurring n-BuLi dissociation only at molar ratios of <1:3. n-BuLi-depleted complex LiLu(n-Bu)3 Cl(tmeda)2 was obtained by treatment of Li2 Lu(n-Bu)5 (tmeda)2 with ClSiMe3 , at the expense of LiCl incorporation. Imamoto's ketone/tertiary alcohol transformation was examined with 1,3-diphenylpropan-2-one, affording 99 % of alcohol.