This contribution reports a high-resolution solid-state 13C NMR study of the organoactinides Cp'2Th(CH3)2, Cp'2Th(13CH3)2, and [Cp'2Th(μ-H)H]2(Cp' = η5-(CH3)5C5) Adsorbed on partially dehydroxylated (PDA) or dehydroxylated (DA) 7-alumina. Cross-polarization (CP) combined with magic angle spinning (MAS) and high-power 1H decoupling produces adsorbate 13C NMR spectra of sufficient resolution and sensitivity to obtain significant structural information. On the basis of the observed 13C chemical shifts, line widths, and field dependence thereof as well as comparison to a number of model systems and dipolar dephasing experiments, methyl transfer from Th to Al on the surface of the support is proposed for the reaction of Cp/ 2Th(13CH3)2with DA. Several types of experiments (Bloch decay, cessation of dipole decoupling, variable contact time) suggest that the adsorbed species are not highly mobile. On the other hand, adsorption of Cp'2Th(13CH3)2on PDA results in protonolysis of the Th-CH3units and the formation of surface Th-O-Al aluminoxy species. Useful correlations with the companion surface and catalysis study are presented. The utility of 13C CPMAS NMR spectroscopy in probing surface-bound metal alkyls (especially in proximity to quadrupolar support nuclei) is emphasized.
ASJC Scopus subject areas
- Colloid and Surface Chemistry