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Closed Access item Neutral and Cationic Alkylmanganese(II) Complexes Containing 2,6-Bisiminopyridine Ligands

Authors:Pérez, Carmen M.
Rodríguez-Delgado, Antonio
Palma Ramírez, Pilar
Álvarez, Eleuterio
Gutiérrez-Puebla, Enrique
Cámpora, Juan
Keywords:Bis(imino)pyridines, Manganese, N ligands, Olefin polymerization, Tritendate ligands
Issue Date:19-Oct-2010
Citation:Chemistry - A European Journal 16(46): 13834-13842 (2010)
Abstract:Manganese alkyl complexes stabilised by 2,6-bis(N,N′-2,6-diisopropyl-phenyl)acetaldiminopyridine (iPrBIP) have been selectively prepared by reacting suitable alkylmanganese(II) precursors, such as homoleptic dialkyls [(MnR2)n] or the corresponding THF adducts [{MnR2(thf)}2] with the mentioned ligand. For R=CH2CMe2Ph or CH2Ph, formally MnI derivatives are produced, in which one of the two R groups migrates to the 4-position of the central pyridine ring in the iPrBIP ligand. In contrast, a true dialkyl complex [MnR2(iPrBIP)] can be isolated for R=CH2SiMe3. In solution, this compound slowly evolves to the corresponding MnI monoalkyl derivative. A detailed study of this reaction provides insights on its mechanism, showing that it proceeds through successive alkyl migrations, followed by spontaneous dehydrogenation. Protonation of [Mn(CH2SiMe3)2(iPrBIP)] with the pyridinium salt [H(Py)2][BAr′4] (Ar′=3,5-C6H3(CF3)2) leads to the cationic species [Mn(CH2SiMe3)(Py)(iPrBIP)]+. Alternatively, the same complex can be produced by reaction of the pyridine complex [{Mn(CH2SiMe3)2(Py)}2] with the protonated ligand salt [HiPrBIP]+[BAr′4]−. This last reaction allows the synthesis of analogous cationic alkylmanganese(II) derivatives, when precursors of type [MnR2(iPrBIP)] are not available. Treatment of these neutral and cationic iPrBIP alkylmanganese derivatives with a range of typical co-catalysts (modified methylaluminoxane (MMAO), B(C6F5)3, trimethyl or triisobutylaluminum) does not lead to active ethylene polymerisation catalysts.
Description:9 páginas, 3 figuras, 1 tabla, 4 esquemas.
Publisher version (URL):http://dx.doi.org/10.1002/chem.201001428
E-ISSNmetadata.dc.identifier.doi = DOI:0947-6539
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