新穎同碳雙碳烯之鈀金屬錯合物的合成、結構鑑定及應用於Suzuki-Miyaura反應

Abstract

同碳雙碳烯或稱為彎曲型重烯，其作為配位基設計與在有機金屬的研究仍屬於新穎的領域。本論文採用簡單的SN2反應合成出兩側取代基相異之同碳雙碳烯，再分別以三級膦與吡啶之衍生分子搭配同碳雙碳烯合成一系列的鈀金屬錯合物，並探討同碳雙碳烯的錯合物結構與其催化活性研究。藉由X-ray晶體結構解析得知，配位基會影響錯合物的順反構型。分子內的π電子相互作用，會使具有苯基的三級膦鈀金屬錯化合物呈現順式結構，此現象也利用變溫的氫核磁共振實驗佐證。 我們將合成的鈀金屬錯合物應用於Suzuki-Miyaura交叉偶合反應，其中以空氣穩定的 [PdCl2(CDC)(PPh3)] 15a催化效果最佳，對於芳香基溴化物與硼酸的推拉電子特性和立體阻礙之官能基皆有良好的耐受性。反應機制的探討指出，空氣中的氧與二甲基亞碸能穩定鈀金屬催化劑，有助於催化循環的進行，此特性對於常見的Suzuki-Miyaura反應的機制及反應性方面是新的見解。

Carbodicarbene so called as bent allene is a divalent carbon (0) or carbon supported by two N-heterocyclic carbene (NHC). It is a strong electron donor ligand for supporting many metal complexes. In this thesis, we reported a preparation of unsymmetrical carbodicarbene via SN2 reaction. We also prepared a series of novel carbodicarbene palladium complexes bearing a different phosphine or pyridine derivatives ligands. The single crystal X-ray structural analysis and spectroscopic studies have been used to understand the trans/cis isomeric behavior of the complexes. The experimental evidences demonstrated that the cis-coordination arrangement in these complexes is resulted from the intramolecular π-π interaction between ligands. In this work, we have also investigated the catalytic properties of these palladium-carbodicarbene complexes. The air-stable complex [PdCl2(CDC)(PPh3)] 5a was found to be highly active in Suzuki-Miyaura cross-coupling reaction for variety of aryl bromides and boronic acids. We also deduced the possible mechanistic pathway involving Pd(0) and Pd(II). The oxygen and trace amount of DMSO play a subtle role in maintaining the active palladium species in the catalytic cycle and providing a new insights on mechanism and reactivity of Suzuki-Miyaura reaction.