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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Reactivity Studies on the Terminal Thorium Imido Metallocene (η5-C5Me5)2Th(═Ndipp)(dmap)
Yi Heng1, Xiaoying Cao1, Wanjian Ding1
1Department of Chemistry, Beijing Normal University, Beijing 100875, China.
None:
Treatment of the thorium dimethyl metallocene (η5-C5Me5)2ThMe2 (1) with dippNH2 (dipp = 2,6-iPr2C6H3) in toluene in the presence of 4-dimethylaminopyridine (dmap) affords the terminal thorium imido metallocene (η5-C5Me5)2Th(═Ndipp)(dmap) (4), accompanied by methane releases. Complex 4 shows broad reactivity in small molecule activation. For example, 4 may activate S8, alkynes, carbodiimides, aldehydes, CS2, organic nitriles and isonitriles, and organic azides, yielding metallaheterocycle, pyridyl amido, oxido, and bis-amido complexes, respectively. Moreover, while 4 forms with Me3PO the adduct (η5-C5Me5)2Th(═Ndipp)(OPMe3) (5), the imido moiety may promote deprotonation reactions as established by its reactions with thiazole, pyridine-N-oxide derivative 2-MepyNO, amine mesitylNH2, hydrazine derivative PhNHNHPh, terminal alkyne PhC≡CH, cyclohexanone, amidate PhCONHPh, imine Ph2C═NH, and nitriles PhCH2CN and C6H11CN. In addition, the imido moiety may also behave as a nucleophile toward PhSiH2Cl, whereas 4 undergoes a Friedel-Crafts type reaction with Me3SiX (X = Cl, I, N3) and Ph3CN3. Lastly, 4 furnishes the bromo amido complex (η5-C5Me5)2Th(Br)[NH(2,6-iPr2-4-(Me5C5)C6H2)] (13) in the presence of CuBr, while the C-C coupling product [(η5-C5Me5)2Th(I)]2[μ-4,4'-(NH-2,6-iPr2C6H2)2] (14) is isolated in the presence of AgI. Furthermore, a comparison with related terminal imido thorium metallocene derivatives demonstrates nicely how different substituents on the cyclopentadienyl and imido ligands influence the reactivity of these compounds.
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