含α-胺基-吡啶雙牙配位基之烯丙基有機鈀錯合物之合成、
異構及催化

本研究合成了一系列含α-胺基-吡啶雙牙配位基之烯丙基有機鈀錯合物 [Pd(η3-C3H4R3)(Pyridine-CHR1NHR2)](BF4) (R1 = 氫、甲基；R2 = 2,6-二異丙基苯基、2,6-二甲基苯基、苯基、三級丁基、異丙基；R3 = 氫、甲基、苯基)。產物運用二維核磁共振技術及X光結晶學加以鑑定。這些錯合物 (R1 = 氫) 具有含掌性中心的胺基以及有取代基的烯丙基，因此在核磁共振光譜中可以觀察到四種主要的非鏡像異構物，而各種異構物的比例主要是由胺基和烯丙基上的取代基的立體效應所主導。在二維NOESY光譜中觀察到四種異構物，彼此會進行快速的異構化轉換。分子流變行為不僅發生在烯丙基部份，也同時發生胺基-吡啶雙牙配位基上，烯丙基基團旋轉以及胺基反轉的能量屏障則是進一步以選擇性NOESY光譜分析和變溫核磁共振實驗加以求得。另外，我們也嘗試將這些有機鈀錯合物應用在不飽和化合物的氫化反應上，並且觀察到不錯的反應活性，然而透過汞毒化、過濾實驗以及穿透式電子顯微鏡影像，顯示催化的活性物質是平均直徑為523奈米的金屬奈米粒子，這可能是由於胺基-吡啶雙牙配位基的弱α-予體能力無法保護零價的鈀物種，因而進一步聚集在一起。

關鍵字

鈀；胺基-吡啶；烯丙基；異構化；流變行為；氫化

並列摘要

A series of cationic allylpalladium(II) complexes with the α-amino-pyridine ligands in the formula of [Pd(η3-C3H4R3)(Pyridine-CHR1NHR2)](BF4) (R1 = H, Me; R2 = 2,6-iPr2C6H3, 2,6-Me2C6H3, Ph, tBu, iPr; R3 = H, Me, Ph) had been synthesized and characterized by 2D NMR and X-ray crystallographic techniques. These complexes (R1 = H) that contained chiral amino group and substituted allyl group afforded four major diastereomers in NMR spectra. The distribution of isomers might be primarily contributed from the steric effect of amino moiety and substituent on allyl group. Rapid isomerization among the isomers was observed in 2D NOESY spectra. The fluxional behavior in solution took place in both allylic moiety and amino-pyridine ligands. The energy barriers of allyl pseudo-rotation and amine inversion were further determined by selective NOESY spectra analysis and variable-temperature NMR experiments. These organopalladium species were also applied to catalyze the hydrogenation of unsaturated substrates and showed comparable activity. However, the mercury poison, filtration experiments and TEM images revealed the active species was metal nanoparticles with average diameter 523 nm. These results might be arisen from the α-amino-pyridine ligands couldn't protect the Pd(0) species from aggregation because of weak σ-donating ability.

並列關鍵字

palladium ； amino-pyridine ； allyl ； isomerization ； dynamic behavior ； fluxional behavior ； hydrogenation

參考文獻

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國際替代計量

含α-胺基-吡啶雙牙配位基之烯丙基有機鈀錯合物之合成、異構及催化

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