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首页> 外文期刊>Organometallics >Tuning of Metal Complex Electronics and Reactivity by Remote Lewis Acid Binding to pi-Coordinated Pyridine Diphosphine Ligands
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Tuning of Metal Complex Electronics and Reactivity by Remote Lewis Acid Binding to pi-Coordinated Pyridine Diphosphine Ligands

机译：通过远程路易斯酸结合pi配位的吡啶二膦配体对金属络合物电子和反应性的调节

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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.
机译：由具有化学可修饰侧基的配体支撑的金属配合物对于控制反应性是令人感兴趣的。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pi系统配位低氧化态金属中心，例如Ni-0和Pd-0。亲电试剂（例如B（C6F5）（3），Me +和BCy2OTf）与可用的吡啶氮结合，分别生成Ni络合物2Ni-B（C6F5）（3），2Ni-Me和2Ni-BCy2OTf。制备了用于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价路易斯酸结合的作用。路易斯酸与2Pd的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，但无路易斯酸的物质不是单体。 Ni配位导致吡啶芳族的破坏，如固态中双键和单键特征的定位所表明的。为无路易斯酸（4Ni）和路易斯酸键合的物质（H +-，Me +-和B（C6F5）（3）-键; 4Ni-H，4Ni-Me和4Ni-B（C6F5）（ 3））分别显示了CO拉伸频率从1930到1966-1976 cm（-1）的显着变化，表明配体电子与金属中心的通讯。 2Ni先与[OMe3] [BF4]，然后再与[NO] [BF4]依次反应，即可得到具有可忽略的金属吡啶相互作用的NO加合物（5Ni）。用硅烷和硼烷处理2Ni会导致吡啶脱芳香化反应，涉及杂原子H键活化，杂原子与吡啶氮结合，氢化物传递至吡啶的邻位。这种反应性表明，吡啶侧基受金属结合的影响极大，从而能够实现基于配体的异常底物活化。所述化学方法突出了通过配体后合成修饰来调节金属中心性能的策略。

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