2 research outputs found
Synthesis and Characterization of Paramagnetic Lanthanide Benzyl Complexes
No full textThe organometallic chemistry of paramagnetic lanthanides
(Ln, from Ce to Yb) is far less developed compared to that of their
diamagnetic counterparts (Sc, Y, La, and Lu). Lack of available starting
materials and characterization methods are the major obstacles. Herein
we report the synthesis and characterization of trisbenzyl complexes
of neodymium, gadolinium, holmium, and erbium. In addition, we introduce
a direct procedure for the synthesis of lanthanide benzyl and iodide
complexes supported by a ferrocene diamide ligand starting from the
corresponding oxides. All newly synthesized compounds were characterized
by X-ray crystallography, <sup>1</sup>H NMR spectroscopy (except for
gadolinium compounds, which were NMR silent), and elemental analysis
Intermolecular β‑Hydrogen Abstraction in Ytterbium, Calcium, and Potassium Tris(dimethylsilyl)methyl Compounds
No full textA series of organometallic compounds containing the trisÂ(dimethylsilyl)Âmethyl
ligand are described. The potassium carbanions KCÂ(SiHMe<sub>2</sub>)<sub>3</sub> and {KCÂ(SiHMe<sub>2</sub>)<sub>3</sub>TMEDA}<sub>2</sub> are synthesized by deprotonation of the hydrocarbon HCÂ(SiHMe<sub>2</sub>)<sub>3</sub> with potassium benzyl. {KCÂ(SiHMe<sub>2</sub>)<sub>3</sub>TMEDA}<sub>2</sub> crystallizes as a dimer with two
types of three-center–two-electron K–H–Si interactions:
side-on coordination of SiH (∠K–H–Si = 102(2)°)
and more obtuse K–H–Si structures (∠K–H–Si
≈ 150°). The divalent calcium and ytterbium compounds
MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>L (M = Ca, Yb; L =
2THF<sub></sub>, TMEDA) are prepared from MI<sub>2</sub> and 2 equiv
of KCÂ(SiHMe<sub>2</sub>)<sub>3</sub>. Low <sup>1</sup><i>J</i><sub>SiH</sub> coupling constants in the NMR spectra, low-energy
ν<sub>SiH</sub> bands in the IR spectra, and short M–Si
distances and small M–C–Si angles in the crystal structures
suggest β-agostic interactions on each CÂ(SiHMe<sub>2</sub>)<sub>3</sub> ligand. The IR assignments of MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>L (L = 2THF<sub></sub>, TMEDA) are supported
by DFT calculations. The compounds MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>L react with 1 or 2 equiv of BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> to give the 1,3-disilacyclobutane {Me<sub>2</sub>SiCÂ(SiHMe<sub>2</sub>)<sub>2</sub>}<sub>2</sub> and MCÂ(SiHMe<sub>2</sub>)<sub>3</sub>HBÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>L or MÂ{HBÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>}<sub>2</sub>L, respectively. In addition,
MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>L compounds react with
BPh<sub>3</sub> to give β-H abstracted products. The compounds
MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>THF<sub>2</sub> react
with SiMe<sub>3</sub>I to yield Me<sub>3</sub>SiH and disilacyclobutane
as the products of β-H abstraction, while MÂ{CÂ(SiHMe<sub>2</sub>)<sub>3</sub>}<sub>2</sub>TMEDA and Me<sub>3</sub>SiI form a mixture
of Me<sub>3</sub>SiH and the alkylation product Me<sub>3</sub>SiCÂ(SiHMe<sub>2</sub>)<sub>3</sub> in a 1:3 ratio
