Haas, 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.


Derivatisierung von Allenyliden-Komplexen sowie Synthese der ersten Nickelallenyliden-Komplexe

2009, Haas, Thomas

Carbene complexes of chromium and tungsten are easily accessible and the variety of the coligand sphere and the carbene offer a wide range of reaction possibilities and synthetic potential. Allenylidene complexes as higher cumuloges of carbene complexes can also be obtained and derived in various ways. The effect of the change in the substitution pattern on the properties of those complexes is yet only rarely examined.
This work is firstly about new ways to derivate pentacarbonyl(allenylidene) complexes of chrom and tungsten, their properties and the possibility of creating polynuclear complexes connecting the metal centers by means of a common pi system.
Secondly, two ways of creating new heteroatom-substituted allenylidene complexes of nickel are introduced. The properties of the nickel allenylidene complexes are compared to those of the corresponding chromium complexes.