Synthesis and reactivity of permethyltantalocene derivatives possessing. eta. sup 3 -allyl,. eta. sup 2 -butadiene,. eta. sup 2 -methylallene, and. eta. sup 1 -alkenylidene ligands. Model studies for the role of surface vinylidenes in the Fischer-Tropsch hydrocarbon-chain-lengthening process

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00047a053· OSTI ID:6069486

Gibson, V C; Parkin, G; Bercaw, J E ^[1]

---

1. California Inst. of Tech., Pasadena (United States)

The reactivity of Cp*{sub 2}TaH{sub 3} (2) (Cp* = {eta}{sup 5}-C{sub 5}Me{sub 5}) toward a number of conjugated dienes has been investigated, and mechanistic pathways have been probed by deuterium-labeling studies. Treatment of 2 with allene at 50C affords Cp*{sub 2}Ta({eta}{sup 3}-C{sub 3}H{sub 5}) (3), which, according to {sup 1}H and {sup 13}C NMR data, is most reasonably described as a tantalabicyclobutane complex. Warming at 80C converts 3, via the intermediate Cp*{sub 2}Ta(H)(HC{triple bond}CMe), to the hydrido propenylidene species Cp*{sub 2}Ta(H)({double bond}C{double bond}C(H)Me) (4). Butadiene reacts with 2 to give sequentially Cp*{sub 2}Ta(H)({eta}{sup 2}-CH{sub 2}{double bond}CHCH{double bond}CH{sub 2}) (8), Cp*{sub 2}Ta(H)({eta}{sup 2}-CH{sub 2}{double bond}C{double bond}C(H)Me) (9), Cp*{sub 2}Ta(H)({double bond}C{double bond}C(H)Et) (10), and Cp*{sub 2}Ta(H)(MeC{triple bond}CMe) (11). 9 exists in the form of two geometrical isomers in which the allene methyl substituent lies in the equatorial coordination plane of the (Cp*{sub 2}Ta) fragment. Mechanistic studies have revealed the importance of {beta}-H elimination from sp{sup 2}-hybridized carbon, allene roll, and 1,2-hydrogen shift processes. Treatment of Cp*{sub 2}Ta(H)({double bond}C{double bond}CH{sub 2}) with excess CH{sub 2}{double bond}PMe{sub 3} leads to the formation of higher order linear-chain vinylidene homologues Cp*{sub 2}Ta(H)({double bond}C{double bond}C(H)R) (R = Me, Et). A mechanism involving the intermediacy of vinylidene species and the migration of {sigma}-alkenyl groups to a metal-bound methylene is proposed for the Fischer-Tropsch hydrocarbon-chain-lengthening process.

• OSTI ID: 6069486
• Journal Information: Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 10:1; ISSN 0276-7333; ISSN ORGND
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010408 -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKENES
ALLENE
BUTADIENE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
CYCLOALKENES
CYCLOPENTADIENE
DIENES
FISCHER-TROPSCH SYNTHESIS
HYDROCARBONS
INFRARED SPECTRA
KINETICS
LIGANDS
MOLECULAR STRUCTURE
NMR SPECTRA
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOMETALLIC COMPOUNDS
POLYENES
REACTION INTERMEDIATES
REACTION KINETICS
SPECTRA
TANTALUM COMPLEXES
TRANSITION ELEMENT COMPLEXES