Haas, Thomas

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Haas
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Thomas
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Ferrocenyl-substituted allenylidene complexes of chromium, molybdenum and tungsten : Synthesis, structure and reactivity

2009, Haas, Thomas, Oswald, Stefan, Niederwieser, Andrea, Bildstein, Benno, Kessler, Florian, Fischer, Helmut

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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Bis(amino)allenylidene complexes by displacement of the MeO group in methoxy allenylidene complexes of chromium and tungsten : Synthesis, DFT calculations and solid-state structures of new bis(amino)allenylidene complexes

2005, Drexler, Matthias, Haas, Thomas, Yu, Sze-Man, Beckmann, Henning, Weibert, Bernhard, Fischer, Helmut

Pentacarbonyl dimethylamino(methoxy)allenylidene tungsten, [(CO)5Wdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashC(OMe)NMe2] (1b), reacts with one equivalent of primary amines, H2NR, by selectively replacing the methoxy group to give dimethylamino(amino)allenylidene complexes, [(CO)5Wdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashC(NHR)NMe2]. When the amine is used in excess both terminal groups, OMe as well as NMe2, are replaced by the primary amino group giving [(CO)5Wdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashC(NHR)2 ]. The NHR substituent in these complexes may be modified by deprotonation with LDA followed by alkylation. The replacement of the methoxy group in 1b by a secondary amino group, NR2, can be achieved by a stepwise process. Addition of Li[NR2] to the Cγ atom of 1b affords an alkynyl tungstate. Subsequent OMe− elimination induced by TMS-Cl/SiO2 yields the allenylidene complexes [(CO)5Wdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashC(NR2)NMe2]. When bidentate diamines are used instead of monoamines both substituents, OMe and NMe2, are replaced and allenylidene complexes are formed in which Cγ constitutes part of a 5-, 6-, or 7-membered heterocycle. The reaction of [(CO)5Crdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashC(OMe)NMe2] (1a) with diethylene triamine affords an allenylidene complex with a heterocyclic endgroup carrying a dangling CH2CH2NH2 substituent. All reactions follow a strict regioselective attack of the nucleophile at Cγ and proceed with good to excellent yields. The addition of N–H to the Cαdouble bond; length as m-dashCβ bond is not observed. By applying either one of these routes nearly any substitution pattern in bis(amino)allenylidene complex can be realized.