胺基-吡啶雙牙配位基的平面甲基鈀催化劑在烯烴聚合 及共聚合反應上的動力學研究

Abstract

含胺基-吡啶雙牙配位基的陽離子鈀金屬錯合物被發現對於烯類的聚合反應及共聚合反應有很好的催化效果。 在此研究工作裡，我們探討兩種類型的催化劑，一為中性金屬錯合物 （[PdCl(LH)(Me)]），另一為陽性金屬錯合物（[Pd(LH)(Me)(MeCN)]+BF4-），其中配位基（LH）為(C5H4N)CH2NHtBu (1)及(C5H4N)CH2NH (2,6-(CH3)2C6H3) (2)，而其相關結構鑑定，可以藉由X光單晶繞射與NMR來完成。由鑑定結果，我們可以發現此類型的鈀金屬錯合物是以一平面四邊形的架構存在的，因此，本身會存在兩種結構異構物，分別為順式和反式異構物。不過，根據含有配位基1的陽性鈀金屬錯合物的氫原子光譜，發現到，其順式異構物在光譜中幾乎是看不到的。 在降冰片烯的聚合反應中，中性及陽性的錯合物都具有不錯的催化活性，尤其是陽性錯合物顯得更好。對於中性錯合物而言，其最好的催化活性大約是60克/莫耳•小時，而陽性錯合物則大約是4350克/莫耳•小時。而在反應中，我們觀察到一稀奇的現象，那就是，順式異構物的催化活性較反式異構物的來的好。 除此之外，我們也利用電噴灑游離質譜法(ESI-MS)分別探討乙烯及降冰片烯的聚合反應及共聚合反應的動力學。從質譜圖中，我們可以看到烯類嵌入的數量會隨時間的增長而增加，且去分析圖譜，可以發現，在降冰片烯的聚合反應中，其活化物種是(LH)Pd-Me，而在烯類的聚合反應中是(LH)Pd-H。另一方面，在共聚合反應中，嵌入降冰片烯的物種主導了整個反應的發展。 在同時，我們藉由推導出的動力學式子去作分析，可以得知速率常數與降冰片烯的濃度間為一線性關係。而添加物，乙腈的濃度對於嵌入反應性有很大的牽制性。

The cationic organopalladium(II) complexes bearing the -amino-pyridine ligands have been found as active catalysts for olefin polymerization and copolymerization. In this work, we studied two types of catalysts, the neutral [PdCl(LH)(Me)]) and cationic [Pd(LH)(Me)(MeCN)]+BF4 - wherein LH= (C5H4N)CH2NHtBu (1), (C5H4N)CH2NH (2,6-(CH3)2C6H3) (2). The identification for such isomers could be readily established by the NMR techniques and X-ray crystallography. These species existed as asymmetric square planar geometry, so that there should be two geometric isomers, cis- form and trans- form, resulted. However, according to 1H NMR spectra of the cationic complex with ligand 1, the isomer of the cis- form in term of relative position of the acetonitrile ligand and the pyridine moiety was negligible. Both neutral and cationic complexes showed good activity for polymerization of norbornene, the cationic species especially. To neutral complexes, the best activity was about 60 g/mole•hr, and it was around 4350 g/mole•hr to the cationic species. Nevertheless, there was the curious detection. The catalytic activity resulting from the cis- isomer was better than the trans- isomer. Furthermore, the kinetics of ethylene/norbornene polymerization and copolymerization was investigated by electrospray ionization tandem mass spectrometry. The spectra showed that the amount of olefin insertion increased with time and the analysis revealed that in the polymerization of norbornene/ethylene, the anterior active species was (LH)Pd-Me, and the posterior active center was (LH)Pd-H. On the other hand, the norbornene inserted species could be served as the leading role in the copolymerization of ethylene/norbornene. At the same time, we could find that there existed linearity between the rate constant and the concentration of norbornene by means of kinetic equations from the data analysis. And the concentration of the additive, acetonitrile would thwart the insertion of norbornene.