雙鉬五重鍵與主族試劑的反應研究

Reactions of the Mo-Mo Quintuple Bond with Main Group Reagents

李威廷(Wei-Ting Lee)

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.2012.00229

摘要

本實驗室以雙氮基脒Li[HC(N-2,6-iPr2C6H3)2]為配基合成出第一個雙鉬五重鍵錯合物Mo2[μ-η2-HC(N-2,6-iPr2C6H3)2]2 (1)，其具有低價數、低配位的特性，使其對小分子有豐富多變的反應性。錯合物1與一當量的二苯基鋅反應，可得錯合物(m-ZnC6H5)(1-C6H5)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (2)，一分子的二苯基鋅進行碳鋅加成反應，苯基鋅以架橋形式配位於雙鉬金屬間。將錯合物2與親電試劑溴化甲苯進一步反應，得到錯合物[m-2-HC(N-2,6-iPr2C6H3)2]Mo[-2:2-C6H5
Zn(C6H5)Br]Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)] (3)，其有一溴原子橋接在鉬原子與鋅原子之間，且有一異丙基上甲基進行碳氫鍵的氧化加成反應。錯合物1也可與四當量的二苯基鋅反應，兩分子的苯基分別以端點形式鍵結於鉬上，形成錯合物(1-C6H5)2Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (5)。此外，錯合物1與兩當量的二甲基鋅反應，得到錯合物(m-2:1-Zn(CH3)2)2Mo2[m-
2-HC(N-2,6-iPr2C6H3)2]2 (6)，其具有兩分子的二甲基鋅配位至雙鉬金屬上，形成兩片架橋配基；若將錯合物6溶於溶劑，會立刻轉變為錯合物(1-CH3)2(THF)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (7)，兩分子的甲基以端點形式鍵結於鉬上，且其中一個甲基上的氫原子與鉬金屬間存在著微弱的agostic作用。
另外，錯合物1與兩當量的三甲基鋁反應，會形成一非常不穩定的錯合物[m-(CH3)2Al(CH3)2]Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)]
(m-H)Al(CH3)[m-2-HC(N-2,6-iPr2C6H3)2]Mo(1-CH3) (8)，一分子的三甲基鋁進行碳-鋁加成反應至鉬鉬金屬鍵上形成架橋配基，且有一鉬金屬與雙氮基脒配基上氮原子的鍵結斷裂，並與鋁原子生成新的氮鋁鍵，最後還有一異丙基上甲基進行了碳氫鍵活化配位於鋁原子上。錯合物8於室溫下會立刻轉變為一中間產物9，其只要接觸到含有氧原子的溶劑即會形成錯合物Mo(Solvent)[m-2-HC(N-2,6-iPr2C6H3)2](m-CH3)Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-
iPr-6-CH(1-CH2)CH3-C6H3)] (Solvent = THF (10), Et2O (11))，具有一個甲基橋接於雙鉬金屬間，並有一異丙基上甲基進行碳氫鍵活化配位於鉬金屬上。將錯合物1與四當量的三乙基鋁反應，會有一分子的三乙基鋁進行碳-鋁加成反應並以架橋形式配位至雙鉬金屬鍵上，且具有兩個乙烯基分別配位於鉬金屬上，形成錯合物(2-C2H4)Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)](m-H)
Al(C2H5)[m-2-HC(N-2,6-iPr2C6H3)2]Mo(2-C2H4) (12)。
錯合物1若與一當量的苯基矽烷反應，則形成錯合物[m-Si(H)C6H5]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (13) ，有一分子的苯基矽烷進行氧化加成至雙鉬金屬上，並脫去一分子的氫氣，且錯合物13可活化微量的水分子進行氧化加成打斷氫氧鍵，形成錯合物(1-H)(1-OH)[m-Si(H)C6H5]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (14)，此外，錯合物13可利用降溫1H-NMR實驗証實其具有一流變行為，並推算出流變過程的速率常速為88.8 s1及活化能為10.59 kcal/mol，而錯合物14則可利用升溫1H-NMR實驗証實也具有一流變行為，同樣可推算出流變過程的速率常速為56.61 s1及活化能為15.75 kcal/mol。除此之外，將錯合物1與一當量的二苯基鍺烷進行反應，一分子的二苯基鍺烷進行氧化加成並脫去一分子的氫分子，形成鍺烯以架橋形式作為配基配位於雙鉬金屬間，形成錯合物[m-Ge(C6H5)2]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (15)。
若將錯合物1與三當量的異氰酸苯酯反應，產生錯合物(m-1:2-PhNCO)(m-2:2-CON(Ph)CONPh)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2
(16)，具有一分子的異氰酸苯酯配位於雙鉬金屬上，反向位置有另兩分子異氰酸苯酯經過碳氮偶合配位於雙鉬上；若與四當量的異氰酸苯酯反應，則有四分子異氰酸苯酯分別兩兩進行碳氮偶合配位於雙鉬上，形成錯合物[m-2:2-CON(Ph)C(O)NPh][m-2:2-CON(Ph)CONPh]Mo2[m-2-HC(N-2,6-iPr2
C6H3)2]2 (17)。此外，錯合物1能有效的催化異氰酸苯酯進行三聚合環化反應，產生1,3,5-異氰酸三苯基酯。

關鍵字

雙鉬五重鍵反應性

並列摘要

The low-coordinate and low-valent quintuple bonded dimolybdenum complex, Mo2[μ-η2-HC(N-2,6-iPr2C6H3)2]2 (1), displays remarkable reactivity toward main group reagents. Undergo an oxidative addition of 1 equiv of diphenylzinc to the Mo-Mo quintuple bond of 1, the dimolybdenum complex, (m-ZnC6H5)(1-C6H5)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (2) is afforded. Subsequent treatment of 2 with 1 equiv of benzyl bromide gives a novel dimolybdenum complex, [m-2-HC(N-2,6-iPr2C6H3)2]Mo[-2:2-C6H5Zn(C6H5)Br]Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)] (3), where one Br atom coordinates between molybdenum and zinc and the molybdenum center accompanies with C-H bond activation of methyl groups. Addition of 4 equiv of diphenylzinc to 1 leads to the formation of the quadruply-bonded dimolybdenum complex, (1-C6H5)2Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (5), which functionalized of the Mo-Mo quintuple bond by two phenyl groups. Reaction of 1 with 2 equiv of dimethylzinc affords (m-2:1-Zn(CH3)2)2Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (6), which is unstable in solvent at room temperature, it transforms into (1-CH3)2(THF)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (7) quickly. Each molybdenum has one phenyl group coordinates on it, and there is weak agostic interaction between the hydrogen atom of methyl group and the molybdenum center.
Treatment of 1 with 2 equiv of trimethylaluminum gives the unstable complex, [m-(CH3)2Al(CH3)2]Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)]
(m-H)Al(CH3)[m-2-HC(N-2,6-iPr2C6H3)2]Mo(1-CH3) (8). The formation of 8 is through the carboalumination of 1 equiv of trimethylaluminum to the Mo-Mo quintuple bond accompanies with a C-H bond activation of methyl group. Complex 8 changes into the intermediate complex 9, which then transforms into Mo(Solvent)[m-2-HC(N-2,6-iPr2C6H3)2](m-CH3)Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-
iPr-6-CH(1-CH2)CH3-C6H3)] (Solvent = THF (10), Et2O (11)) when it contacts solvents like tetrahydrofuran or ether. Complex 10 and 11 contain one methyl group bridging between two molybdenum centers and there is C-H bond activation of methyl group to the molybdenum. Reaction of 1 with 4 equiv of triethylaluminum gives (2-C2H4)Mo[m-2-HC(N-2,6-iPr2C6H3)(N-2-iPr-6-CH(1-CH2)CH3-C6H3)](m-
H)Al(C2H5)[m-2-HC(N-2,6-iPr2C6H3)2]Mo(2-C2H4) (12). The formation of 12 is through the carboalumination of 1 equiv of triethylaluminum to the Mo-Mo quintuple bond accompanies with a C-H bond activation of methyl group, and there are two vinyl groups coordinate to the molybdenum centers.
Treatment of 1 equiv of phenylsilane to 1 gives rise to the formation of [m-Si(H)C6H5]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (13), which is formed via an oxidative addition of one molecular phenylsilane to the dimolybdenum quintuple bond, and then releases one molecular hydrogen gas. Besides, Complex 13 can activate a small amount of water to give the novel product, (1-H)(1-OH)[m-Si(H)C6H5]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (14). Complex 13 and 14 exhibit the fluxional behavior, which have been characterized by variable temperature NMR. Introduction of 1 equiv of diphenylgermane to 1 leads to the formation of a lantern-type quadruply-bonded dimolybdenum complex, [m-Ge(C6H5)2]Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (15).
Treatment of 1 with 3 equiv and 4 equiv of phenylisocyanate affords (m-1:2-PhNCO)(m-2:2-CON(Ph)CONPh)Mo2[m-2-HC(N-2,6-iPr2C6H3)2]2 (16) and [m-2:2-CON(Ph)C(O)NPh][m-2:2-CON(Ph)CONPh]Mo2[m-2-HC (N-2,6-iPr2
C6H3)2]2 (17), respectively. Complex 16 is formed via a C-N coupling in a “head-to-tail” mode, and one molecular phenylisocyanate coordinates on molybdenum centers. On the other hand, via C-N coupling, complex 17 has two pairs of two molecules of phenylisocyanate coordinate to the molybdenum centers. Beside, 1 can effectively catalyzes the cyclotrimerization of phenylisocyanate under mild conditions, affords high yield of 1,3,5-triphenylisocyanurate.

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