以參鈀金屬錯合物催化氫分子對炔類之順式加成反應

Z-Selective Semi-Reduction of Alkynes with Molecular Hydrogen Catalyzed by a Tri-Palladium Complex

王昱皓(Yu-Hao Wang)

指導教授 ： 劉緒宗

國立臺灣大學/理學院/化學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802582

摘要

多牙氮配位基2,7-bis(2-pyridyl)-1,8-napthyridine (bpnp)是具有四個吡啶結構的配體，其多金屬錯合物已被廣泛合成，並應用在催化反應。在bpnp的雙金屬錯合物中，金屬之間的距離可以在約3 Å左右，使其金屬之間可以有鍵結的可能；在本篇工作中，嘗試以鈀(0)與鈀(II)之金屬前驅物，希望合成出金屬鍵架構的錯合物。遂利用bpnp與零價前驅物Pd2(dba)3以及二價前驅物PdCl2(PhCN)2在二氯甲烷中反應，卻意外地獲得具有C2對稱性的參鈀金屬錯合物[Pd3(bpnp)2Cl2]Cl2 (Pd3)。它在水與甲醇類的溶解度極高，因此在此溶劑將此錯合物作為催化劑，在最佳化條件之下，炔類分子可以被氫化而得到相對應的順式烯類為主產物。
其中以四氫呋喃與水作為共溶劑，並在30℃且1 atm之條件下氫化，二苯基乙炔(diphenylacetylene)可以成功轉化爲反式二苯基乙烯(cis-1,2-diphenylethene)，只有非常少量的烯類被過度氫化成飽和烴。然而如果增加氫氣壓力或是提高反應溫度，也能將烯類氫化至烷類。除此之外，稍微修改反應條件後，此催化劑也能將疊氮化物(azide)氫化而得到相對應的胺類(amine)。本方法具有溫和的反應溫度、低催化劑量、短時間，以及方便的後處理等優點。
最後本篇工作使用密度泛函理論(DFT, Density Functional Theory)進行理論計算。在泛含以及基底函數組的選用上，非金屬原子的部分使用B3LYP/6-31+G(d,p)，而鈀原子則使用B3LYP/LANL2DZ，以此針對反應機制進行了詳細地探討。

關鍵字

鈀錯合物 ； 有機金屬 ； 缺類還原

並列摘要

2,7-bis(2-pyridyl)-1,8-napthyridine (bpnp) is a tetra-pyridinyl ligand, which is capable of accommodating dinuclear species. In our work, we have obtained a palladium complex chelated with bpnp in a trimetallic fashion. Complexation of bpnp with equal molar amount of Pd2(dba)3 and (PhCN)2PdCl2 in CH2Cl2 at ambient temperature, a complex [Pd3(bpnp)2Cl2]Cl2 with C2 symmetry was obtained. This tri-palladium complex, upon activated by NH3-BH3, was found to be catalytic active on hydrogenation of unsaturated hydrocarbons particularly for the semi-hydrogenation of alkyne into cis-alkenes. By manipulating reaction conditions, alkynes molecules can be converted into the corresponding Z-alkenes selectively. Typically, diphenylacetylene was transferred into cis-1,2-diphenylethene in THF/H2O at 30℃ under 1 atm of hydroden gas in 92% yield, accompanied with a minor amount of over-hydrogenated byproduct. Further reduction to alkanes can be achieved under a higher pressure of hydrogen or at raising temperature. Furthermore, other functional groups such as arylnitrile and azide can be hydrogenated to the corresponding amine by modification of the conditions slightly. This protocol has several advantages such as mild conditions, low catalyst loading, short reaction time, and convenient workup. The reaction mechanism was investigated by DFT calculation at the levels of B3LYP/6-31+G(d,p) and B3LYP/LANL2DZ. Furthemore, the use of tri-palladium complex in reduction of bicarbonate under various mild conditions was investigated.

並列關鍵字

Alkynes ； Semi-Reduction ； Palladium Complex

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