Ferrocenyl-substituted allenylidene complexes of chromium, molybdenum and tungsten: Synthesis, structure and reactivity |
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Authors: | Thomas Haas Andrea Niederwieser Florian Kessler |
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Affiliation: | a Fachbereich Chemie, Universität Konstanz, Fach M727, 78457 Konstanz, Germany b Institut für Allgemeine, Anorganische und Theoretische Chemie, Fakultät für Chemie und Pharmazie, Universität Innsbruck, Innrain 52a, 6020 Innsbruck, Austria |
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Abstract: | Bis(ferrocenyl)-substituted allenylidene complexes, [(CO)5MCCCFc2] (1a-c, Fc = (C5H4)Fe(C5H5), M = Cr (a), Mo (b), W (c)) were obtained by sequential reaction of Fc2CO with Me3Si-CCH, KF/MeOH, n-BuLi, and [(CO)5M(THF)]. For the synthesis of related mono(ferrocenyl)allenylidene chromium complexes, [(CO)5CrCCC(Fc)R] (R = Ph, NMe2), three different routes were developed: (a) reaction of the deprotonated propargylic alcohol HCCC(Fc)(Ph)OH with [(CO)5Cr(THF)] followed by desoxygenation with Cl2CO, (b) Lewis acid induced alcohol elimination from alkenyl(alkoxy)carbene complexes, [(CO)5CrC(OR)CHC(NMe2)Fc], and (c) replacement of OMe in [(CO)5CrCCC(OMe)NMe2] by Fc. Complex 1a was also formed when the mono(ferrocenyl)allenylidene complex [(CO)5CrCCC(Fc)NMe2] was treated first with Li[Fc] and the resulting adduct then with SiO2. The replacement route (c) was also applied to the synthesis of an allenylidene complex (7a) with a CC spacer in between the ferrocenyl unit and Cγ of the allenylidene ligand, [(CO)5CrCCC(NMe2)-CCFc]. The related complex containing a CHCH spacer (9a) was prepared by condensation of [(CO)5CrCCC(Me)NMe2] with formylferrocene in the presence of NEt3. The bis(ferrocenyl)-substituted allenylidene complexes 1a-c added HNMe2 across the Cα-Cβ bond to give alkenyl(dimethylamino)carbene complexes and reacted with diethylaminopropyne by regioselective insertion of the CC bond into the Cβ-Cγ bond to afford alkenyl(diethylamino)allenylidene complexes, [(CO)5MCCC(NEt2)CMeCFc2]. The structures of 5a, 7a, and 9a were established by X-ray diffraction studies. |
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Keywords: | Allenylidene complexes Ferrocenyl complexes Chromium Molybdenum Tungsten |
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