Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds
| Autor: | Aradhana Pindwal, KaKing Yan, Aaron D. Sadow, Bradley M. Schmidt, Arkady Ellern, Cheolbeom Bae, Smita Patnaik, Igor I. Slowing |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
chemistry.chemical_classification
010405 organic chemistry Chemistry Praseodymium Inorganic chemistry chemistry.chemical_element General Chemistry Nuclear magnetic resonance spectroscopy 010402 general chemistry 01 natural sciences Biochemistry Catalysis 0104 chemical sciences Crystallography chemistry.chemical_compound Colloid and Surface Chemistry X-ray crystallography Kinetic isotope effect Homoleptic Isostructural Alkyl Group 2 organometallic chemistry |
| Zdroj: | Journal of the American Chemical Society. 139(46) |
| ISSN: | 1520-5126 |
| Popis: | Homoleptic tris(alkyl) rare earth complexes Ln{C(SiHMe2)3}3 (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) are synthesized in high yield from LnI3THFn and 3 equiv of KC(SiHMe2)3. X-ray diffraction studies reveal 1a–d are isostructural, pseudo-C3-symmetric molecules that contain two secondary Ln↼HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe2)3}3 and DFT calculations. The Ln↼HSi and terminal SiH exchange rapidly on the NMR time scale at room temperature, but the two motifs are resolved at low temperature. Variable-temperature NMR studies provide activation parameters for the exchange process in 1a (ΔH⧧ = 8.2(4) kcal·mol–1; ΔS⧧ = −1(2) cal·mol–1K–1) and 1a-d9 (ΔH⧧ = 7.7(3) kcal·mol–1; ΔS⧧ = −4(2) cal·mol–1K–1). Comparisons of lineshapes, rate constants (kH/kD), and slopes of ln(k/T) vs 1/T plots for 1a and 1a-d9 reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing fi... |
| Databáze: | OpenAIRE |
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