Isolation of a cationic chromium(II) species in a catalytic system for ethylene tri- and tetramerization
Isolation of a cationic chromium(II) species in a catalytic system for ethylene tri- and tetramerization
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DOI：
10.1021/om050886l
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发表时间：
2006-01-30
期刊：
影响因子：
2.8
通讯作者：
Duchateau, R
中科院分区：
文献类型：
--
作者：
Jabri, A;Crewdson, P;Duchateau, R
用Me3Al处理乙烯四聚化催化剂前驱体[PNP]CrCl3得到新的二价催化剂前驱体{[PNP]Cr(m-CI)AlMe3} [ClAlMe3](0.34) [Me4Al](0.66)(.)0.125（己烷）（.）0.25（甲苯）(1)。1的形成意味着还原到二价状态、阳离子化和配体乱序。这一物种在被MAO激活后表现出与三价前体相似的催化活性，这一事实表明，将金属还原为二价状态是形成实际催化活性物种的一步。CrCl2(THF)(2)与[PNP]反应失败表明，阳离子化和获得第二配体和桥接ClAlMe3残基是这种新的二价催化剂前驱体稳定的核心。
Treatment of the ethylene tetramerization catalyst precursor [PNP]CrCl3 with Me3Al afforded the new divalent catalyst precursor {[PNP]Cr(m-CI)AlMe3} [ClAlMe3](0.34) [Me4Al](0.66)(.)0.125(hexane)(.)0.25 (toluene) (1). The formation of 1 implies reduction to the divalent state, cationization, and ligand scrambling. The fact that this species displays, upon activation with MAO, a catalytic activity similar to that of the trivalent precursor indicates that reduction of the metal to the divalent state is a step toward the formation of the actual catalytically active species. The failure of CrCl2(THF)(2) to react with [PNP] indicates that cationization and acquisition of the second ligand and of a bridging ClAlMe3 residue are central to the stabilization of this new divalent catalyst precursor.