Synthesis and 171Yb- Nuclear Magnetic Resonance Spectra of Ytterbium(II) Aryloxides and 2> (X = OR' or NR2) (R' = C6H2Bu-t2-2,6-Me-4, R = SiMe3, thf = tetrahydrofuran)

Article abstract of DOI:10.1039/DT9950001435

Crystalline homo- and hetero-leptic ytterbium(II) aryloxides derived from bulky 2,6-di-tert-butyl-4-methylphenol (R'OH) were prepared as follows: (a) 1 from 2 R'OH and I (R = SiMe3); (b) <2> 2 by desolvating 1 or from <2> II and 4 R'OH; and (c) <2> 3 from II and 2 R'OH or II and 2.Single-crystal X-ray diffraction studies established complex 1 to be monomeric with a distorted tetrahedral configuration and 2 to be dimeric with asymmetrically bridging ^-OR' ligands.Complexes 1-3 were characterised by multinuclear (1H, 13C, 29Si and 171Yb) NMR spectroscopy and elemental (C, N, H) analysis.Variable-temperature 1H and 13C NMR spectral data for 2 led to ΔG(excit) for the terminal/bridge ^-OR' site-exchange process.The known aryloxide 4 was obtained from 1 and an excess of tetrahydrofuran (thf); reacting 1 with the appropriate stoichiometric amount of thf, pyridine (py) or 1,2-bis(dimethylphosphino)ethane (dmpe) yielded 5, 6 or 7, respectively.The δ <171Yb-<1H>> NMR spectral data for complexes 4-7 showed that displacement of diethyl ether from 1 (δ 238 at 193 K) by another neutral coligand had a marked effect on the magnitude of the chemical shift, ranging from δ 286 at 233 K for 4 to δ 999 at 296 K for 7.

Full text of DOI:10.1039/DT9950001435

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