MIXED-LIGAND LANTHANIDE COMPLEXES .8. PARAMAGNETIC SHIFT INDUCED BY PR(FOD)3PZ AND PR(FOD)3PYZ IN THE NMR SPECTRUM OF DI-N-BUTYL ETHER

摘要

Two adducts of Pr(fod)(3), Pr(fod)(3)pz and Pr(fod)(3)pyz, where pz stands for pyrazole and pyz for pyrazine, have been scanned as potential NMR shift reagents using di-n-butyl ether. Although di-n-butyl is a very weak donor, complexes associate with the base and induce large hyperfine isotropic shifts in the resonance frequencies of the magnetic substrate nuclei. The t-butyl resonances of the complexes are strongly shifted upfield in the presence of the substrate. This observation, together with the fact that the spectrum of the substrate is unaffected by the addition of any amount of the complexes, are taken as evidence that the specific coordination of the complexes to the substrate occurs through the agency of the oxygen lone-pair electrons. [References: 14]