ISSN:
1572-8862
Schlagwort(e):
C-C bond formation
;
polynuclear
;
diruthenium
;
triruthenium
;
alkyne oligomerization
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Maschinenbau
,
Physik
Notizen:
Abstract Studies on C-C bond formation between simple hydrocarbon species such as CH2, C=CH2, CH=CH2, CH2=CH2, CH2=C=CH2 and CH≡CH at a diruthenium center suggest that the process is promoted when the dimetal center can readily compensate for the two electrons “lost” in the formation of the new C-C bond. Thus, whereas μ-CH2 and ethene combine only under forcing conditions, the combination of μ-CH2 with allene or ethyne, which have additional π-electrons available for coordination, occurs readily at room temperature. Likewise, the availability of uncoordinated π-electrons in μ-C=CH2 allows vinylidene to link rapidly with ethene at room temperature. Alkyne complexes [Ru2(CO)(μ-RC≡CR)(η-C5H5)2] (R=CF3 or Ph) react only under vigorous conditions with additional alkyne to give [Ru2(CO)(μ-C4R4) (η-C5H5)2], but give these same species at room temperature in the presence of acid, shown to be due to the intermediacy of highly reactive 30-electron μ-vinyl cations. Thermally, alkyne linking proceedsvia three-alkyne species [Ru2(μ-C6R6)(η-C5H5)2] to a four-alkyne complex [Ru2(μ-C8R8)(η-C5H5)2], containing an unprecedented C8 ligand composed of a C6 ring with a C2 “tail.” Treatment of [Ru2(CO)(μ-RC≡CR)(η-C5H5)2] with unsaturated metal fragments gives trimetal complexes such as [Ru3(CO)5(μ3-CF3C≡CCF3) (η-C5H5)2]. The MeCN derivative of this species undergoes unusual linking processes on reaction with additional alkyne to giveinter alia [Ru3(CO)3(μ3-CCF3){μ3-C3(CF3)3}(η-C5H5)2], arising from alkyne cleavage, and [Ru3(CO)3{μ3-C4(CF3)2(CO2Me)2}(η-C5H5)2], a closo-pentagonal bipyramidal Ru3C4 cluster.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00702746
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