CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines: Formation of New Cyclobutenylidene and Pentatrienylidene Complexes
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- 作者：Gerhard Roth ; David Reindl ; Martin Gockel ; Carsten Troll ; and Helmut Fischer
- 刊名：Organometallics
- 出版年：1998
- 出版时间：March 30, 1998
- 年：1998
- 卷：17
- 期：7
- 页码：1393 - 1401
- 全文大小：172K
- 年卷期：v.17,no.7(March 30, 1998)
- ISSN：1520-6041
文摘
The reaction of the diarylallenylidene complexes[(CO)5M=C=C=C(C6H4R-p)2](M = Cr(1), W (2); R = H (a), Me(b), OMe (c), NMe2 (d))with the ynamines MeC
CNEt2 andPhCCNEt2 affords two products: alkenylallenylidene(3, 5) and cyclobutenylidene complexes (4, 6). The alkenylallenylidenecomplexes[(CO)5M=C=C=C(NEt2)C(R')=C(C6H4R-p)2] (R' = Me, M = Cr (3), W(5), R = H (a), Me (b), OMe(c), NMe2 (d); R' = Ph, M = Cr(3),R = OMe (e), NMe2 (f)) are formedvia cycloaddition of the CC bond of the ynamine totheC2=C3 bond of 1 and 2,respectively, and subsequent cycloreversion. Thecyclobutenylidenecomplexes[(CO)5M=C-C(R')=C(NEt2)- C=C(C6H4R-p)2](R' = Me, M = Cr (4), W (6), R=H (a), Me (b), OMe (c),NMe2 (d); R' = Ph, M = Cr (4), R= OMe (e), NMe2 (f)) areformedby cycloaddition of the ynamines to the C1=C2bond of 1 and 2. The compounds 3,4a-c, 5,and 6a-c are stable at room temperature.In contrast, 4d-f and 6ddecompose on contactwith air, light, or silica. Complex 3d wascharacterized by an X-ray structural analysis.The product ratios 3/4 and5/6 strongly depend on the solvent and thesubstitution patternof both the allenylidene complexes 1 and 2 andthe ynamine. In general, decreasing polarityof the solvent increasingly favors formation of cyclobutenylidenecomplexes. The solventdependence indicates that the transition state for the formation of4 and 6 is significantlyless polar than that for the formation of 3 and5. The ratios 3/4 and5/6 increase in theseries a < b < c < d.Kinetic measurements of the reaction of 1c,dwith the ynaminesMeCCNEt2 and PhCCNEt2 reveal that thecomplex pairs 3,4 and 5,6are formed inparallel pathways with an associative rate-determining step for each.The reactions followsecond-order kinetics, first-order in the concentrations of theallenylidene complexes 1,2and of the ynamines. The activation enthalpies
H
are small, and the activationentropiesS are strongly negative.S is more negative for the formationof the alkenylallenylidenecomplexes than for the formation of the cyclobutenylidene complexes.
CNEt2 andPhCCNEt2 affords two products: alkenylallenylidene(3, 5) and cyclobutenylidene complexes (4, 6). The alkenylallenylidenecomplexes[(CO)5M=C=C=C(NEt2)C(R')=C(C6H4R-p)2] (R' = Me, M = Cr (3), W(5), R = H (a), Me (b), OMe(c), NMe2 (d); R' = Ph, M = Cr(3),R = OMe (e), NMe2 (f)) are formedvia cycloaddition of the CC bond of the ynamine totheC2=C3 bond of 1 and 2,respectively, and subsequent cycloreversion. ThecyclobutenylideneCNEt2 and PhCCNEt2 reveal that thecomplex pairs 3,4 and 5,6are formed inparallel pathways with an associative rate-determining step for each.The reactions followsecond-order kinetics, first-order in the concentrations of theallenylidene complexes 1,2and of the ynamines. The activation enthalpiesH are small, and the activationentropiesS are strongly negative.S is more negative for the formationof the alkenylallenylidenecomplexes than for the formation of the cyclobutenylidene complexes.