Synthesis and reactivity of zirconium and hafnium complexes incorporating chelating diamido-N-heterocyclic-carbene ligands |
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| Affiliation: | 1. Departamento de Química, Universidad del Valle, AA 25360 Cali, Colombia;2. Escuela de Química, Universidad Industrial de Santander, 680002 Bucaramanga, Colombia;3. Departamento de Física, Universidad del Valle, AA 25360 Cali, Colombia;4. Centro de Excelencia en Nuevos Materiales (CENM), Universidad del Valle, AA 25360 Cali, Colombia;1. Ural Federal University, 620002 Ekaterinburg, Russia;2. Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russia;1. Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France;2. Université de Lorraine, CNRS, L2CM, F-54000 Nancy, France;1. Institute of Chemistry, Academia Sinica, Nangang, Taipei 115, Taiwan, ROC;2. Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC;3. Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA;1. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova 28, Moscow, 119991, Russia;2. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 117901, Russia |
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| Abstract: | Early transition metal complexes employing a diamido N-heterocyclic carbene (NHC) ligand set (denoted [NCN]) render the centrally disposed NHC moiety stable to dissociation. Aminolysis reactions with the mesityl-substituted ligand precursor (Mes[NCN]H2) and M(NMe2)4 (M = Zr, Hf) provide bis(amido)-NHC-metal complexes that can be further converted to chloro and alkyl derivatives. Activation of Mes[NCN]M(CH3)2 with [Ph3C][B(C6F5)4] yields {Mes[NCN]MCH3}{B(C6F5)4}, which is surprisingly inactive for the polymerization of 1-hexene. The zirconium cation did, however, show moderate ability to catalytically polymerize ethylene. The hafnium dialkyls are thermally stable with the exception of the diethyl complex, Mes[NCN]Hf(CH2CH3)2, which undergoes β-hydrogen transfer and subsequent C–H bond activation with an ortho-methyl substituent on the mesityl group. The hafnium dialkyl complexes also insert carbon monoxide and substituted isocyanides to yield η2-acyls and η2-iminoacyls, respectively. In some circumstances, further C–C bond coupling occurs to yield enediolates and eneamidolate metallocycles. The molecular structures of Mes[NCN]Hf(CH2CHMe2)2, Mes[NCN]Hf(η2-(2,6-Me2C6H3NCCH3)(CH3), Mes[NCN]Hf(η2-(2,6-Me2C6H3NCCH3)2, Mes[NCN]Hf(OC(CH3) C(CH3)NXy), and [Mes[NCN]Hf(OC(iBu)C(iBu)O)]2 are included. |
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