σ- or π-Coordination? Complexes of Univalent Gallium Salts with Aromatic Nitrogen Bases
σ- or π-Coordination? Complexes of Univalent Gallium Salts with Aromatic Nitrogen Bases
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DOI：
10.1002/ejic.201402360
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发表时间：
2014-09-01
影响因子：
2.3
通讯作者：
Krossing, Ingo
中科院分区：
文献类型：
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作者：
Lichtenthaler, Martin R.;Stahl, Florian;Krossing, Ingo
为了回答关于镓在其氧化态+1下是否有利于芳香族氮碱的σ-或π-配位的问题，我们使[Ga（C6 H5 F）（2）]（+）[Al（ORF）（4）]（-）{R-F = C（CF 3）}与吡嗪和2，6-二叔丁基-4-甲基吡啶（DTBMP）反应。在此过程中，我们获得了第一个三配位的、非螯合的、均配的镓（I）的N-给体配合物：[Ga-（吡嗪）（3）]（+）[Al（ORF）（4）]（-），其中每个镓（I）阳离子以三角金字塔的方式由三个η（1）-给体吡嗪配体配位。因此，镓（I）阳离子有利于σ-配位而不是π-配位。根据反应条件的不同，由于吡嗪的双功能性，还得到了{[Ga（mu-吡嗪）（2）（eta（1）-吡嗪）]（+）[Al（ORF）（4）]（-）}（无穷大）的一维配位聚合物。用通常用作质子清除剂的空间要求高的DTBMP，分离出混合络合物[Ga（C6 H5 F）（2）（DTBMP）]（+）[Al（ORF）（4）]（-），从而证明DTBMP是“非亲核”的看法是不正确的。通过多核NMR研究和在RI-BP 86/SV（P）水平上进行的密度泛函分析证实了结构发现。
To answer the question as to whether gallium in its oxidation state +1 favors a sigma- or a pi-coordination of aromatic nitrogen bases, we reacted [Ga(C6H5F)(2)](+)[Al(ORF)(4)](-) {R-F = C(CF3)} with pyrazine and 2,6-di-tert-butyl-4-methylpyridine (DTBMP). In doing so, we obtained the first tricoordinate, nonchelated, homoleptic N-donor complex of gallium(I): [Ga-(pyrazine)(3)](+)[Al(ORF)(4)](-), in which each gallium(I) cation is coordinated in a trigonal-pyramidal fashion by three eta(1)-donating pyrazine ligands. Hence, the gallium(I) cations favor sigma- over pi-coordination. Depending on the reaction conditions, and due to the bifunctionality of pyrazine, 1D coordination polymers of {[Ga(mu-pyrazine)(2)(eta(1)-pyrazine)](+)[Al(ORF)(4)](-)}(infinity) were also obtained. With the sterically demanding DTBMP, which is conventionally used as a proton scavenger, the mixed complex [Ga(C6H5F)(2)(DTBMP)](+)[Al(ORF)(4)](-) was isolated, thus proving incorrect the perception of DTBMP being "non-nucleophilic". The structural findings were confirmed by multinuclear NMR investigations and density functional performed at the RI-BP86/SV(P) level.