Tuning of Metal Complex Electronics and Reactivity by Remote Lewis Acid Binding to π-Coordinated Pyridine Diphosphine Ligands
Tuning of Metal Complex Electronics and Reactivity by Remote Lewis Acid Binding to π-Coordinated Pyridine Diphosphine Ligands
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DOI：
10.1021/acs.organomet.5b00562
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发表时间：
2015-10-12
期刊：
影响因子：
2.8
通讯作者：
Agapie, Theodor
中科院分区：
文献类型：
--
作者：
Horak, Kyle T.;VanderVelde, David G.;Agapie, Theodor
由具有可化学修饰的侧基的配体支撑的金属配合物对于控制反应性具有重要意义。我们报告了包含路易斯酸结合位点的多齿膦配体框架的配位化学和反应性。 3,5-双(2-膦基苯基)-吡啶通过膦供体和杂环的π体系配位低氧化态金属中心，例如Ni-0和Pd-0。亲电试剂如 B(C6F5)(3)、Me+ 和 BCy2OTf 与可用的吡啶氮结合，分别生成 Ni 配合物 2Ni-B(C6F5)(3)、2Ni-Me 和 2Ni-BCy2OTf。制备了 Pd 的类似化合物（2Pd、2Pd-B(C6F5)(3) 和 2Pd-H）。通过单晶 X 射线衍射研究和光谱学评估了路易斯酸结合的效果。路易斯酸与 2Pd 结合导致金属与杂环 pi 系统之间更强的 eta(1) 相互作用。 Ni 以 eta(2) 方式结合，但不含路易斯酸的物质不是单体。 Ni配位会导致吡啶芳香性的破坏，正如固态中双键和单键特征的局部化所表明的那样。针对路易斯酸游离（4Ni）和路易斯酸结合物质（H+-、Me+-和B(C6F5)(3)-结合；4Ni-H、4Ni-Me和4Ni-B(C6F5)(3)）制备了CO加合物，显示CO伸缩频率分别从1930到1966-1976 cm(-1)显着变化，表明配体电子与金属中心的通讯。 2Ni 依次与 [OMe3] [BF4] 和 [NO] [BF4] 反应，得到具有可忽略不计的金属吡啶相互作用的 NO 加合物 (5Ni)。用硅烷和硼烷处理 2Ni 会导致吡啶脱芳构化，涉及杂原子-H 键活化，杂原子与吡啶氮结合，氢化物传递到吡啶的邻位。这种反应性表明，吡啶侧链受到金属结合的显着影响，从而实现了不寻常的基于配体的底物激活。所描述的化学强调了通过配体合成后修饰来调节金属中心特性的策略。
Metal complexes supported by ligands with chemically modifiable pendant groups are of interest for controlling reactivity. We report on the coordination chemistry and reactivity of a multidentate phosphine ligand framework that contains a Lewis acid binding site. 3,5-Bis(2-phosphinophenyl)-pyridine coordinates low-oxidation-state metal centers such as Ni-0 and Pd-0 via the phosphine donors and the pi system of the heterocycle. Electrophilic reagents such as B(C6F5)(3), Me+, and BCy2OTf bind the available pyridine nitrogen, generating the Ni complexes 2Ni-B(C6F5)(3), 2Ni-Me, and 2Ni-BCy2OTf, respectively. Analogous compounds were prepared for Pd (2Pd, 2Pd-B(C6F5)(3), and 2Pd-H). The effect of Lewis acid binding was evaluated by single-crystal X-ray diffraction studies and spectroscopy. Lewis acid binding to 2Pd leads to a stronger eta(1) interaction between the metal and the heterocycle pi system. Ni binds in an eta(2) fashion, but the Lewis acid free species is not monomeric. Ni coordination results in disruption of pyridine aromaticity, as indicated by localization of double- and single-bond character in the solid state. CO adducts were prepared for Lewis acid free (4Ni) and Lewis acid bound species (H+-, Me+-, and B(C6F5)(3)-bound; 4Ni-H, 4Ni-Me, and 4Ni-B(C6F5)(3)) that show a significant shift of the CO stretching frequency from 1930 to 1966-1976 cm(-1), respectively, indicating communication of ligand electronics to the metal center. An NO adduct (5Ni) with negligible metal pyridine interactions was obtained upon sequential reaction of 2Ni with [OMe3] [BF4] and then [NO] [BF4]. Treatment of 2Ni with silanes and boranes results in pyridine dearomatization involving heteroatom-H bond activation, with the heteroatom binding to the pyridine nitrogen and the hydrides delivered to the ortho position of pyridine. This reactivity demonstrates that the pendant pyridine is drastically affected by metal binding, enabling unusual ligand-based substrate activation. The described chemistry highlights a strategy for tuning the properties of metal centers by ligand postsynthetic modifications.