Catalytic oligomerization of terminal alkynes promoted by organo-f-complexes
Conference
·
OSTI ID:250096
- Technion-Israel Institute of Technology, Haifa (Israel)
Organoactinides of the type Cp*{sub 2}AcMe{sub 2} (Cp*=C{sub 5}Me{sub 5}; Ac=Th, U) are active catalyst precursors for the oligomerization of terminal alkynes HC{triple_bond}CR (R=alkyl, aryl, SiMe{sub 3}). The regioselectivity and the extent of oligomerization strongly depend on the alkyne substituent R, whereas the catalytic reactivity is similar for 1 and 2. In the presence of one of these organoactinides, for example, HCCSiMe{sub 3} regioselectively oligomerizes to the head-to-tail dimer 3 (5%) and the trimer 4 (95%). 1 and 2 react with the terminal alkynes, releasing methane, to the corresponding bisacetylide complexes which are active species and in the catalytic reactions. The bisacetylide complex ({eta}{sup 5}-C{sub 5}Me{sub 5}){sub 2}U(CCPh){sub 2} was identified by proton NMR spectroscopy. Subsequent insertion of alkyne molecules in the actinide-carbon {sigma}-bonds leads to the formation of actinide-alkenyl complexes. The turnover limiting step is the release of the organic oligomer from the actinide-organyl complex. A species of the latter has been spectroscopically characterized in the trimerization reaction of HCCSiMe{sub 3}. In this poster, the catalytic reactivity of the actinide alkyls 1 and 2 with various mono-substituted alkynes as well as the spectroscopic characterization of the key organometallic intermediate complexes in the catalytic cycle and a detailed mechanistic discussion are given.
- OSTI ID:
- 250096
- Report Number(s):
- CONF-9508100--
- Country of Publication:
- United States
- Language:
- English
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