含二胺基吡啶配基之低價數多鍺金屬與鉻多重鍵錯合物的合成及結構研究

Synthesis and Characterization of Low-Coordinate Multinuclear Germanium and Multiply-Bonded Dichromium Complexes Supported by Bulky Pyridyl Diamides

游憲政(Hsien-Cheng Yu)

指導教授 ： 蔡易州

國立清華大學/理學院/化學系/碩士(2012年)

https://doi.org/10.6843/NTHU.2012.00223

摘要

本實驗室利用Li2[N2Ndipp] (N2Ndipp = 4-methyl-2,6-(N-2,6-iPr2C6H3)2 pyridine)為配基合成出雙核鍺一價化合物K2Ge2[N2Ndipp]2 (2)，將2與GeCl2‧dioxane和SnCl2反應，分別得到[GeCl]2Ge2[N2Ndipp]2 (3)與[SnCl]2Ge2[N2Ndipp]2 (4)。我們利用化合物2中具有高電荷密度的鍺(I)-鍺(I)金屬鍵與ZnI2反應，也成功合成出多金屬鏈化合物[ZnI]2Ge2[N2Ndipp]2(THF) (5)，有趣的是，其中心金屬鍺(I)-鍺(I)距離也從2.5168(6)Å縮短為2.4060(6)Å。當我們將2與由正己烷配成1M的GeCl4反應，可以得到V字形角錐狀的化合物 [GeCl2][GeCl]2[N2Ndipp]2 (8)，其GeCl4被還原成GeCl2並且以架橋的形式嵌入於鍺-鍺金屬鍵中間。另外，我們將3和4與KNCS反應，得到兩端鍺金屬上的Cl-離子由NCS-基團所取代的[GeNCS]2Ge2[N2Ndipp]2 (6)與[SnNCS]2Ge2[N2Ndipp]2 (7)。
有趣的是，當我們將3分別溶於冰正己烷或冰四氫呋喃溶劑中，並加入由正己烷配成1M的GeCl4反應，前者得到主要產物為鍺五員環 [(GeCl2)(GeCl)4][N2Ndipp]2 (9)，而後者其主要產物則為鍺四員環[GeCl]4[N2Ndipp]2 (10)，主要是由於受到溶劑效應(solvent effect)的影響所致。
我們將Li2[N2Ndipp]與CrCl2反應，合成出Cr2[N2Ndipp]2 (THF)2 (12)。本實驗室曾以Li2[N2Ndipp]與CrCl3反應後，再直接以KC8進行還原反應，可以分離出雙鉻(I)五重鍵金屬錯合物[(Et2O)KCr(N2Ndipp)]2 (11)，我們也能將12與KC8進行還原反應，發現可以得到高產率的11。當我們將11與CaI2反應，令人驚奇的是，成功合成出新穎的雙鉻(I)五重鍵Cr2Ca [N2Ndipp]2(THF)2 (15)，其鉻(I)-鉻(I)間距離為1.7356(7) Å，較11(1.7443(10) Å)縮短了約0.01 Å。另外，我們將11與AlMe3反應，得到三個鉻金屬原子以直線排列且不對稱的[μ-CH3]2Cr3[N2Ndipp]2 (THF) (16)，其鉻(II)-鉻(II)間距離分別為1.8989(6) Å與2.6283(6) Å。
其他嘗試中，我們首先利用Li[HC(NDipp)2] (NDipp = N-2,6- iPr2C6H3)配基與CrCl2得到Cr[HC(NDipp)2]2，接著加入GeCl2‧dioxane進行反應，成功合成出[(GeCl)(μ-Cl)Cr][HC(NDipp)2]2 (17)。之後，將17與還原劑LiAlH4進行反應，成功合成出具有鉻-鍺金屬鍵且新奇的 [(GeCl)(CrH)][HC(NDipp)2]2 (18)，其鉻(II)-鍺(II)鍵長為2.5610(16) Å。
以上所有合成出來的產物，皆已經過核磁共振光譜和元素分析鑑定。透過單晶X-ray繞射解析，我們也清楚了解其分子結構。

關鍵字

多鍺金屬與鉻多重鍵錯合物

並列摘要

The low-valent and low-coordinate digermanium complex, K2Ge2[N2Ndipp]2 (2), was synthesize by the sterically hindered three-nitrogen donor ligand, Li2[N2Ndipp] (N2Ndipp = 4-methyl-2,6-(N-2,6-iPr2C6H3)2 pyridine). The bond length of Ge(I)-Ge(I) in 2 is 2.5168(6) Å. Treatment of 2 with GeCl2‧dioxane and SnCl2 gives two linear tetranuclear mixed-valence complexes, [MCl]2Ge2[N2Ndipp]2 (3: M = Ge; 4: M = Sn), respectively. These complexes 2, 3, and 4 are starting materials to synthesize the following low-coordinate multinuclear complexes.
Treatment of 2 with ZnI2 also produces a tetranuclear mixed-valence Zn(II)-Ge(I)-Ge(I)-Zn(II) complex, [ZnI]2Ge2[N2Ndipp]2(THF) (5), where the internal Ge(I)-Ge(I) bond length is significantly shortened to 2.4060(6)Å. Reaction of 2 with 1M stock solution of GeCl4 in hexane results in the formation of a inverted V-shape pyramidal trinuclear mixed-valence Ge(III)-Ge(II)-Ge(III) complex, [GeCl2][GeCl]2[N2Ndipp]2 (8), where GeCl4 is reduced to GeCl2 and bridges between two Ge(III) atoms.
Similar to molecular wire, reaction of 3 or 4 with KNCS undergoes SN2 reaction, giving tetranuclear complexes, [MNCS]2Ge2[N2Ndipp]2 (6: M = Ge; 7: M = Sn). Interestingly, due to the solvent effect, reaction of 3 and 1 equivalent of GeCl4 in n-hexane gave rise to the formation of cyclic pentanuclear germane, [(GeCl2)(GeCl)4][N2Ndipp]2 (9) as the major product. On the contrary, if this reaction is carried out in THF, cyclic tetranuclear germane, [GeCl]4[N2Ndipp]2 (10) is the major product instead.
Besides, treatment of Li2[N2Ndipp] with CrCl2 gives the complex Cr2[N2Ndipp]2(THF)2 (12). Upon reduction of 12 with KC8 leads to a quintuply-bonded complex, [(Et2O)KCr(N2Ndipp)]2 (11), which was already reported by our lab. Unfortunately, reaction of 11 with CaI2 failed to give a tetranuclear complex; instead it formed an amazing quintuply-bonded complex, Cr2Ca [N2Ndipp]2(THF)2 (15), where the Cr(I)-Cr(I) bond length is 1.7356(7) Å, shorter than 11, in which the Cr(I)-Cr(I) bond length is 1.7443(10) Å. Moreover, reaction of 11 with AlMe3 produces an asymmetric trichromium complex, [μ-CH3]2Cr3 [N2Ndipp]2(THF) (16). The Cr-Cr bond lengths are 1.8989(6) Å and 2.6283(6) Å, respectively.
In addition, the reaction of amidinate ligand, Li[HC(NDipp)2] (NDipp = N-2,6-iPr2C6H3) and CrCl2 produces the Cr[HC(NDipp)2]2. Treatment of the mixture of Cr[HC(NDipp)2]2 and GeCl2‧dioxane gives [(GeCl)(μ-Cl)Cr][HC(NDipp)2]2 (17). There is one chloride that bridges between germanium and chromium atoms. The addition of LiAlH4 to 17 leads to the isolation of heterodinuclear complex, [(GeCl)(CrH)][HC(NDipp)2]2 (18). The distance of Ge-Cr is 2.5610(16) Å and is assigned a single bond.
All the synthesized products have been characterized by NMR spectroscopy and elemental analysis, and their molecular structures have been determined by single crystal X-ray crystallography.

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