Chromium(II)/(III) Complexes Bearing Phosphino-N-Heterocyclic Carbene and N-Chelating N-Heterocyclic Carbene Ligands and Their Use in Ethylene Oligomerization

IF 2.5 3区化学 Q2 CHEMISTRY, INORGANIC & NUCLEAR

Organometallics Pub Date : 2024-12-30 DOI:10.1021/acs.organomet.4c0045810.1021/acs.organomet.4c00458

Somnath Bhattacharya, Boshra Atwi, Koushani Kundu, Wolfgang Frey and Michael R. Buchmeiser*,

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Abstract

The bidentate Cr(III) phosphino-N-heterocyclic carbene (NHC) complex [(1-(2,6-diisopropylphen-1-yl)-3-(1-diphenylphosphinoeth-2-ylimidazol-2-ylidene)CrCl₃(THF)] (Cr1) as well as the Cr(II) and Cr(III) complexes [(1-methyl-3-(2-amido-N-(2,6-diisopropylpheny-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr₂-(μ-Cl)₄] (Cr2), [(1-methyl-3-(2-amido-N-(2-biphen-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr₂-(μ-Cl)₄] (Cr3), [(1-methyl-3-(2-amido-N-(2,6-diisopropylpheny-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr₂-(μ-Cl)₄] (Cr4), [(1-methyl-3-(2-amido-N-(2,6-diisopropylpheny-1-yl)phen-1-ylimidazol-2-ylidene)Cr(benzyl)₂(THF)] (Cr5), [(1-methyl-3-(2-amido-N-(2,6-diisopropylpheny-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr] (Cr7), [(1-methyl-3-(2-amido-N-(2,6-diisopropylpheny-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr₂-(μ-Cl)₂(Cl)₂(THF)₂] (Cr8), [(1-methyl-3-(2-amido-N-(2-biphen-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr] (Cr10), [(1-methyl-3-(2-amido-N-(2-biphen-1-yl)phen-1-ylimidazol-2-ylidene)Cr-(μ-Cl)₂(1-methyl-3-(2-amido-N-(2-biphen-1-yl)phen-1-ylimidazol-2-ylidene)₂Cr] (Cr11) containing a bidentate N-chelating NHC, as well as the Cr(II) cyclic alkylamino carbene (CAAC) complex [(CAAC)₂CrCl₂] (Cr6, CAAC = 1-(2,6-diisopropylpheny-1-yl)-3,3,5,5-tetramethyltetrahydropyrrol-2-ylidene) have been prepared. Cr1, Cr4, Cr7, Cr8, and Cr10–Cr12 were characterized by single-crystal X-ray analysis. The molecular structure of Cr4 features a binuclear complex comprising two Cr(II) metal centers where each metal center adopts a distorted square planar geometry, whereas Cr11 represents a noteworthy addition to the rare class of structurally characterized mixed-valence Cr-complexes composed of two nonequivalent Cr centers with formal Cr(II) and Cr(III) oxidation states. In the presence of methylalumoxane (MAO) as a cocatalyst, the novel chromium complexes display catalytic activity in ethylene oligomerization. Complex Cr2, with an N-diisopropylphenyl group, shows ca. 7 times higher polymerization activity (8.1 kg mol Cr^–1 h^–1 bar^–1) than Cr3 (1.1 kg mol Cr^–1 h^–1 bar^–1) bearing a bulky, yet flexible N-biphen-1-ylamine unit, indicating that less bulky ligands can enhance catalytic activity in chelated Cr complexes. The Cr(II)-CAAC complex Cr6 possesses increased activity compared to a structurally similar Cr(II)-NHC complex.

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含磷- n -杂环卡宾和n -螯合n -杂环卡宾配体的铬(II)/(III)配合物及其在乙烯低聚反应中的应用

双配位基的铬(III) phosphino-N-heterocyclic碳烯(NHC)复杂[(1 - (2,6-diisopropylphen-1-yl) 3 - (1-diphenylphosphinoeth-2-ylimidazol-2-ylidene) CrCl3(四氢呋喃)](Cr1)以及Cr (II)和铬(III)复合物(1-methyl-3——(2-amido-N - (2, 6-diisopropylpheny-1-yl) phen-1-ylimidazol-2-ylidene) 2 Cr2 -(μcl) 4] (Cr2), [(1-methyl-3 - (2-amido-N - (2-biphen-1-yl) phen-1-ylimidazol-2-ylidene) 2 Cr2——(μcl) 4] (Cr3), [(1-methyl-3——(2-amido-N - (2, 6-diisopropylpheny-1-yl) phen-1-ylimidazol-2-ylidene) 2 Cr2 -(μcl) 4] (Cr4),[(1-甲基-3-（2-氨基- n-（2,6-二异丙基苯基-1-基）苯-1-基咪唑-2-基）Cr（苯）2(THF)] (Cr5),[(1-甲基-3-（2-氨基- n-（2,6-二异丙基苯基-1-基）苯-1-基咪唑-2-基）2Cr] (Cr7),[(1-甲基-3-（2-氨基- n-（2,6-二异丙基苯基）苯-1-基咪唑-2-基）2Cr2-(μ-Cl)2(Cl)2(THF)2] (Cr8),[(1-甲基-3-（2-氨基- n-（2-联苯-1-基）苯-1-基咪唑-2-基）2Cr] (Cr10)，制备了含有双齿n螯合NHC的[(1-甲基-3-(2-氨基- n-（2-联苯-1-基）phen1 - ylimidazole -2-ylidene)Cr-(μ-Cl)2(1-甲基-3-(2-氨基- n-（2-联苯-1-基）phen1 - ylimidazole -2-ylidene)2Cr] （Cr11）和Cr（II）环烷基氨基羰基（CAAC）配合物[(CAAC)2CrCl2] （Cr6, CAAC = 1-（2,6-二异丙基苯基-1-基）-3,3,5,5-四甲基四氢吡啶-2-ylidene）。Cr1、Cr4、Cr7、Cr8和Cr10-Cr12用单晶x射线分析表征。Cr4的分子结构是由两个Cr（II）金属中心组成的双核配合物，其中每个金属中心都采用扭曲的方形平面几何形状，而Cr11则是由两个具有正式Cr（II）和Cr（III）氧化态的非等效Cr中心组成的罕见的混合价Cr配合物的一个值得注意的补充。在甲基铝氧烷（MAO）作为助催化剂存在下，新型铬配合物在乙烯低聚反应中表现出催化活性。含有n-二异丙基苯基的配合物Cr2的聚合活性（8.1 kg mol Cr -1 h-1 bar-1）比含有庞大但灵活的n-联苯-1-亚胺单元的Cr3 （1.1 kg mol Cr -1 h-1 bar-1）高约7倍，这表明体积较小的配体可以增强螯合Cr配合物的催化活性。与结构相似的Cr(II)-NHC复合物相比，Cr(II)-CAAC复合物Cr6具有更高的活性。

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来源期刊

Organometallics 化学-无机化学与核化学

CiteScore

5.60

自引率

7.10%

发文量

382

审稿时长

1.7 months

期刊介绍： Organometallics is the flagship journal of organometallic chemistry and records progress in one of the most active fields of science, bridging organic and inorganic chemistry. The journal publishes Articles, Communications, Reviews, and Tutorials (instructional overviews) that depict research on the synthesis, structure, bonding, chemical reactivity, and reaction mechanisms for a variety of applications, including catalyst design and catalytic processes; main-group, transition-metal, and lanthanide and actinide metal chemistry; synthetic aspects of polymer science and materials science; and bioorganometallic chemistry.