Organometallic molecule-inorganic surface coordination and catalytic chemistry. In situ CPMAS NMR delineation of organoactinide adsorbate structure, dynamics, and reactivity

A 75.4-MHz {sup 13}C CPMAS NMR spectroscopic study of the surface structures and reaction chemistry of a series of organoactinides adsorbed on various inorganic supports is reported. On Lewis acid surfaces such as dehydroxylated Al{sub 2}O{sub 3}, MgCl{sub 2}, and SiO{sub 2}-Al{sub 2}O{sub 3}, it is found that organothorium complexes of the type Cp{prime}{sub 2} ThR{sub 2} (Cp{prime} = {eta}{sup 5}-(CH{sub 3}){sub 5}C{sub 5}; R = {sup 13}CH{sub 3}, {sup 13}CH{sub 2}{sup 13}CH{sub 3}), Cp{prime}ThR{sub 3} (R = {sup 13}CH{sub 2}C{sub 6}H{sub 5}), and Cp{sub 3}ThR (Cp = {eta}{sup 5}-C{sub 5}H{sub 5}; R = {sup 13}CH{sub 3}), undergo heterolytic Th-C scission to transfer an alkyl anion to the surface forming Cp{prime}{sub 2} ThR, Cp{prime}ThR{sub 3{minus}n}, or Cp{sub 3}Th adsorbate species with cation-like character. Probe studies with paramagnetic Cp{prime}{sub 2}U({sup 13}CH{sub 3}){sub 2} indicate that the majority of the transferred methyl groups of Cp{prime}{sub 2}U({sup 13}CH{sub 3}){sub 2}/DA and Cp{prime}{sub 2}U({sup 13}CH{sub 3}){sub 2}/MgCl{sub 2} are located {approx gt}5 {angstrom} from the U(IV) ion.