Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
Chemistry. 2010 Dec 10;16(46):13834-42. doi: 10.1002/chem.201001428.
Manganese alkyl complexes stabilised by 2,6-bis(N,N'-2,6-diisopropyl-phenyl)acetaldiminopyridine ((iPr)BIP) have been selectively prepared by reacting suitable alkylmanganese(II) precursors, such as homoleptic dialkyls [(MnR(2))(n)] or the corresponding THF adducts [{MnR(2)(thf)}(2)] with the mentioned ligand. For R=CH(2)CMe(2)Ph or CH(2)Ph, formally Mn(I) derivatives are produced, in which one of the two R groups migrates to the 4-position of the central pyridine ring in the (iPr)BIP ligand. In contrast, a true dialkyl complex [MnR(2)((iPr)BIP)] can be isolated for R=CH(2)SiMe(3). In solution, this compound slowly evolves to the corresponding Mn(I) 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(CH(2)SiMe(3))(2)((iPr)BIP)] with the pyridinium salt [H(Py)(2)][BAr'(4)] (Ar'=3,5-C(6)H(3)(CF(3))(2)) leads to the cationic species Mn(CH(2)SiMe(3))(Py)((iPr)BIP). Alternatively, the same complex can be produced by reaction of the pyridine complex [{Mn(CH(2)SiMe(3))(2)(Py)}(2)] with the protonated ligand salt H(iPr)BIPBAr'(4). This last reaction allows the synthesis of analogous cationic alkylmanganese(II) derivatives, when precursors of type [MnR(2)((iPr)BIP)] are not available. Treatment of these neutral and cationic (iPr)BIP alkylmanganese derivatives with a range of typical co-catalysts (modified methylaluminoxane (MMAO), B(C(6)F(5))(3), trimethyl or triisobutylaluminum) does not lead to active ethylene polymerisation catalysts.
通过反应合适的烷基锰(II)前体，如均二烷基[(MnR(2))(n)]或相应的四氢呋喃加合物[{MnR(2)(thf)}(2)]与所述配体，可以选择性地制备由 2,6-双(N,N'-2,6-二异丙基-苯)乙二醛亚氨基吡啶((iPr)BIP)稳定的锰烷基配合物。对于 R=CH(2)CMe(2)Ph 或 CH(2)Ph，生成了形式上的 Mn(I)衍生物，其中两个 R 基团之一迁移到中央吡啶环的 4-位在(iPr)BIP 配体中。相比之下，可以分离出真正的二烷基配合物[MnR(2)((iPr)BIP)]，其中 R=CH(2)SiMe(3)。在溶液中，该化合物缓慢地演变为相应的 Mn(I)单烷基衍生物。对该反应的详细研究提供了对其机制的深入了解，表明它通过连续的烷基迁移，然后自发脱氢进行。用吡啶盐[H(Py)(2)][BAr'(4)]（Ar'=3,5-C(6)H(3)(CF(3))(2)）质子化[Mn(CH(2)SiMe(3))(2)((iPr)BIP)]导致阳离子物种Mn(CH(2)SiMe(3))(Py)((iPr)BIP)。或者，也可以通过反应吡啶配合物[{Mn(CH(2)SiMe(3))(2)(Py)}(2)]与质子化配体盐H(iPr)BIPBAr'(4)来制备相同的配合物。最后一种反应允许合成类似的阳离子烷基锰(II)衍生物，当没有可用的[MnR(2)((iPr)BIP)]类型的前体时。用一系列典型的共催化剂（改性甲基铝氧烷（MMAO）、B(C(6)F(5))(3)、三甲基或三异丁基铝）处理这些中性和阳离子(iPr)BIP 烷基锰衍生物不会导致活性乙烯聚合催化剂。
