Alkyl-eta2-alkene niobocene and tantalocene complexes with the allyldimethylsilyl-eta5-cyclopentadienyl ligand: synthesis, NMR studies and DFT calculations |
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Authors: | Nicolás Pilar Royo Pascual Galakhov Mikhail V Blacque Olivier Jacobsen Heiko Berke Heinz |
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Institution: | Departamento de Química Inorganica, Facultad de Química, Universidad de Alcalá, Campus Universitario, E-28871, Alcalá de Henares, Spain. |
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Abstract: | Group 5 metal complexes M(eta5-C5H5)eta5-C5H4SiMe2(CH2-eta]2-CH=CH2)]X] (M = Nb, X = Me, CH2Ph, CH2SiMe3; M = Ta, X = Me, CH2Ph) and Ta(eta5-C5Me5)eta5-C5H4SiMe2(CH2-eta2-CH=CH2)]X] (X = Cl, Me, CH2Ph, CH2SiMe3) containing a chelating alkene ligand tethered to a cyclopentadienyl ring have been synthesized in high yields by reduction with Na/Hg (X = Cl) and alkylation with reductive elimination (X = alkyl) of the corresponding metal(iv) dichlorides M(eta5-Cp)eta5-C5H4SiMe2(CH2CH=CH2)]Cl2] (Cp = C5H5, M = Nb, Ta, Cp = C5Me5, M = Ta). These chloro- and alkyl-alkene coordinated complexes react with CO and isocyanides CNtBu, CN(2,6-Me2C6H3)] to give the ligand-substituted metal(III) compounds M(eta5-Cp)eta5-C5H4SiMe2(CH2CH=CH2)]XL] (X = Cl, Me, CH2Ph, CH2SiMe3). Reaction of the chloro-alkene tantalum complex with LiNHtBu results in formation of the imido hydride derivative Ta(eta5-C5Me5)eta5-C5H4SiMe2(CH2CH=CH2)]H(NtBu)]. NMR studies for all of the new compounds and DFT calculations for the alkene-coordinated metal complexes are compared with those known for related group 4 metal cations. |
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