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CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines :  Formation of New Cyclobutenylidene and Pentatrienylidene Complexes

CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines :  Formation of New Cyclobutenylidene and Pentatrienylidene Complexes

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ROTH, Gerhard, David REINDL, Martin GOCKEL, Carsten TROLL, Helmut FISCHER, 1998. CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines :  Formation of New Cyclobutenylidene and Pentatrienylidene Complexes. In: Organometallics. 17(7), pp. 1393-1401. ISSN 0276-7333. eISSN 1520-6041. Available under: doi: 10.1021/om971102+

@article{Roth1998CCCou-23047, title={CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines :  Formation of New Cyclobutenylidene and Pentatrienylidene Complexes}, year={1998}, doi={10.1021/om971102+}, number={7}, volume={17}, issn={0276-7333}, journal={Organometallics}, pages={1393--1401}, author={Roth, Gerhard and Reindl, David and Gockel, Martin and Troll, Carsten and Fischer, Helmut} }

Gockel, Martin Gockel, Martin 1998 2013-06-10T06:49:07Z Roth, Gerhard CC-Coupling Reactions of Group 6 Allenylidenes with Ynamines :  Formation of New Cyclobutenylidene and Pentatrienylidene Complexes Troll, Carsten Fischer, Helmut Reindl, David Organometallics ; 17 (1998), 7. - S. 1393-1401 Fischer, Helmut The reaction of the diarylallenylidene complexes [(CO)5MCCC(C6H4R-p)2] (M = Cr (1), W (2); R = H (a), Me (b), OMe (c), NMe2 (d)) with the ynamines MeCCNEt2 and PhCCNEt2 affords two products:  alkenylallenylidene (3, 5) and cyclobutenylidene complexes (4, 6). The alkenylallenylidene complexes [(CO)5MCCC(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 formed via cycloaddition of the CC bond of the ynamine to the C2C3 bond of 1 and 2, respectively, and subsequent cycloreversion. The cyclobutenylidene = 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)) are formed by cycloaddition of the ynamines to the C1C2 bond of 1 and 2. The compounds 3, 4a−c, 5, and 6a−c are stable at room temperature. In contrast, 4d−f and 6d decompose on contact with air, light, or silica. Complex 3d was characterized by an X-ray structural analysis. The product ratios 3/4 and 5/6 strongly depend on the solvent and the substitution pattern of both the allenylidene complexes 1 and 2 and the ynamine. In general, decreasing polarity of the solvent increasingly favors formation of cyclobutenylidene complexes. The solvent dependence indicates that the transition state for the formation of 4 and 6 is significantly less polar than that for the formation of 3 and 5. The ratios 3/4 and 5/6 increase in the series a < b < c < d. Kinetic measurements of the reaction of 1c,d with the ynamines MeCCNEt2 and PhCCNEt2 reveal that the complex pairs 3,4 and 5,6 are formed in parallel pathways with an associative rate-determining step for each. The reactions follow second-order kinetics, first-order in the concentrations of the allenylidene complexes 1,2 and of the ynamines. The activation enthalpies ΔH are small, and the activation entropies ΔS are strongly negative. ΔS is more negative for the formation of the alkenylallenylidene complexes than for the formation of the cyclobutenylidene complexes. 2013-06-10T06:49:07Z eng Roth, Gerhard Reindl, David deposit-license Troll, Carsten

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