雙鉬四鍵錯合物與有機鋅、主族試劑及小分子的反應

Reactions of the Mo-Mo Quadruple Bond with Organozinc / Main Group Reagents and Small Molecules

詹益泉(Chan, Yi Chuan)

指導教授 ： 蔡易州

國立清華大學/理學院/化學系/碩士(2015年)

摘要

本論文以高立體阻礙的PhB[N-2,6-iPr2C6H3)]2雙牙雙胺配基合成出的雙鉬金屬四重鍵Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2(C7H8) (1)，用其低配位與低價數的性質與有機鋅、主族試劑及小分子進行反應。錯合物1與一當量有機鋅化合物如二苯基鋅、二甲基鋅及二乙基鋅反應，得到雙鉬三鍵錯合物cis-(R-Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Ph (2)，Me (3)，Et (4))，有機鋅化合物進行氧化加成以順式(cis)方式配位在雙鉬原子上，並脫去鋅原子。
將錯合物1與與第十六族的硫元素反應則會得到兩種產物，為具有一個硫原子配基之錯合物(μ-S)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (5)及過硫配基錯合物(μ-κ2-S2)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (6)，將其近一步地利用鉀石墨(KC8)還原，則會得到具有超硫化配基之錯合物(κ2-S2Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (7)，而將錯合物7與三當量的三苯基膦反應，可成功將錯合物5單離出。但將錯合物1與第十六族的硒或碲反應卻只能得到單一原子架橋之產物(μ-E)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (E = Se (8)，Te (9))。有趣的是錯合物9於溶劑下時容易分解回錯合物1。
將錯合物1與一當量有機疊氮化合物如1-叠氮金剛烷及叠氮三甲基矽烷反應則脫去氮氣，得到[μ-RN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = 1-Ad (10)，TMS (11))，為氮原子架橋在鉬金屬間的亞胺基雙鉬三鍵錯合物。
將錯合物1與一當量烷基腈分子如丙腈及異丁腈反應，可得腈基配位在雙鉬金屬上之雙鉬三鍵錯合物[μ-η2-(R)CN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Et (12)，iPr (13))，形成燈籠型結構；而錯合物1會與兩當量的具有拉電子特性的4-溴苯腈反應，經由碳原子進行碳-碳鍵耦合，可得雙鉬三鍵錯合物[μ-η2-NC(4-BrC6H4)C(4-BrC6H4)N]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (14)，但錯合物14上的碳-氮鍵與金屬鉬-鉬鍵整體不共平面，並無芳香性，此例子有別以往雙鉬五重鍵之[2+2+2]環加成反應。此外錯合物1與一當量苯乙炔反應，會形成燈籠型雙鉬三鍵錯合物(μ-η1:η1-C6H5CCH)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (15)。
最後，試圖降低配基的立體阻礙，以增加其反應性，改用PhB[NLi(2,6-Et2C6H3)]2雙牙雙胺配基合成出的雙鉬金屬三重鍵syn-Cl2Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2 (16)，在進一步地利用鉀石墨(KC8)還原，可得到兩個雙鉬金屬四重鍵中間配位了氘代苯的錯合物{Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2}2(C6D6) (17)，而中間的氘代苯因受到雙鉬金屬四重鍵的擠壓而形成椅型結構，也因此氘代苯不易脫離，迫使錯合物17反應性不如錯合物1。

關鍵字

四鍵 ； 有機鋅 ； 主族試劑 ； 雙鉬四鍵

並列摘要

Abstract
The low-valent and low-coordinate quadruply-bonded dimolybdenum complex, Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2(C7H8) (1), shows interesting reactivities toward organozinc, main group reagents and small molecules.
Treatment of 1 with one equiv of organozinc reagents, such as diphenylzinc, dimethylzinc, and diethylzinc, leads to the formation of dimolybdenum complex, cis-(R-Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Ph (2), Me (3), Et (4)), which are formed via an oxidative addition of one molecular organozinc reagents to 1, and then release one zinc atom.
Treatment of 1 with S8 gives two products. One is sulfide complex (μ-S)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (5) and the other is persulfide complex (μ-κ2-S2)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (6). Subsequent introduction of KC8 to the product mixture results in the isolation of the supersulfido complex (κ2-S2Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (7). Moreover, complex 5 can be isolated from complex 7 by adding three equivs of triphenylphosphine. However, treatment of 1 with Se or Te only leads to (μ-E)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (E = Se (8), Te (9)). Besides, complex 9 is unstable in organic solvents and it slowly decomplses back to complex 1.
Furthermore, the reaction of 1 with one equiv of organic azides, such as 1-adamantyl azide and trimethylsilyl azide, extrudes one equiv of dinitrogen molecule and gives a dimolybdenum imido complex, [μ-RN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = 1-Ad (10), TMS (11)).
Reaction of 1 with one equiv of alkyl nitriles, such as propionitrile and isobutyronitrile, respectively, affords [μ-η2-(R)CN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Et (12), iPr (13)).
However, treatment of 1 with two equivs of 4-bromobenzonitrile gives a [2+2+2] cycloaddition dimolybdenum adduct, [μ-η2-NC(4-BrC6H4)C(4-BrC6H4)N]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (14), which is formed via a C-C coupling. In contrast to the [2+2+2] dimolybdenum adducts formed from Mo-Mo quintuple bonded complexes, the central C2N2Mo2 six-membered ring of complex 14 is not planar, so it does not have aromatic property.
Treatment of 1 with one equiv of phenylacetylene leads to characterization of the [2+2] dimolybdenum cycloadduct, (μ-η1:η1-C6H5CCH)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (15),
Finally, the dimolybdenum complex syn-Cl2Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2 (16) stabilized by the less bulky ligand PhB[N-2,6-Et2C6H3]2 can be prepared. However, subsequent KC8 reduction leads to the characterization of an arene-bridged tetranuclear complex {Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2}2(C6D6) (17), in which two dimolybdenum units are bridged by a benzene-d6.
The bridged benzene-d6 in 7 is not planar but reather reduced to adopt a chair form and it is not labile. As a result, complex 17 is much less reactive than complex 1.

並列關鍵字

Quadruple Bond ； Organozinc ； Main Group ； Small Molecules

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