高曉娜,韓紅斐,郭志強(qiáng),魏學(xué)紅,*

(1.運(yùn)城學(xué)院 應(yīng)用化學(xué)系,山西 運(yùn)城 044000;2.山西大學(xué) 化學(xué)化工學(xué)院,山西 太原 030006;3.山西大學(xué) 大型科學(xué)儀器研究中心,山西 太原 030006)

胍基鋰化合物的合成、晶體結(jié)構(gòu)及催化異氰酸酯三聚反應(yīng)

高曉娜1,2,韓紅斐2,郭志強(qiáng)3,魏學(xué)紅2,3*

(1.運(yùn)城學(xué)院 應(yīng)用化學(xué)系,山西 運(yùn)城 044000;2.山西大學(xué) 化學(xué)化工學(xué)院,山西 太原 030006;3.山西大學(xué) 大型科學(xué)儀器研究中心,山西 太原 030006)

以二乙胺、正丁基鋰和不對(duì)稱的碳化二亞胺PhN=C=NCy反應(yīng),生成一個(gè)新的胍基鋰化合物,[(Et)2NC(NCy)(NPh)LiOEt2]2(1),該化合物通過元素分析、1H NMR、13C NMR和X-ray單晶衍射等完整的結(jié)構(gòu)表征。另外,研究了該胍基鋰化合物(1)對(duì)芳香異氰酸酯三聚合成異氰脲酸酯的催化效果。實(shí)驗(yàn)結(jié)果表明,在室溫條件下,當(dāng)催化劑1和底物的摩爾比為0.5%,反應(yīng)時(shí)間為10 min時(shí),三聚合成異氰脲酸酯的產(chǎn)率最高可達(dá)到99%。

胍基鋰化合物;合成;晶體結(jié)構(gòu);催化

由于異氰脲酸酯分子中存在穩(wěn)定的六元環(huán)結(jié)構(gòu),且環(huán)上沒有活潑氫存在,這種結(jié)構(gòu)使它具有剛性、阻燃性、熱穩(wěn)定性和水解穩(wěn)定性等特點(diǎn),這些與生俱來的特點(diǎn)促使這類物質(zhì)有著廣闊的應(yīng)用領(lǐng)域,尤其是在建筑外墻使用的保溫隔熱材料方面。聚氨酯硬泡(RPUF)是目前廣泛應(yīng)用于外墻的保溫材料,但是這種材料存在著阻燃性和耐熱性差的劣勢,如果在聚氨酯鏈上引入異氰脲酸酯,改性過的聚氨酯可以在150℃高溫下長期連續(xù)使用,其先天不足的缺點(diǎn)能得到極大的改善[15]。另外,異氰脲酸酯還應(yīng)用在需要耐水、透明且耐撞擊的共聚物合成樹脂的制備上[16]。鑒于異氰脲酸酯廣闊的應(yīng)用領(lǐng)域,因此開發(fā)新的催化劑來高效制備異氰脲酸酯是許多化學(xué)工作者的研究熱點(diǎn)。

本論文以二乙胺、正丁基鋰和不對(duì)稱的碳化二亞胺PhN=C=NCy為起始原料,合成了一個(gè)新的胍基鋰化合物,并利用NMR、X-ray單晶衍射等測試手段對(duì)該化合物進(jìn)行了完整的結(jié)構(gòu)表征。另外,我們將這種胍基鋰化合物應(yīng)用于異氰酸酯的三聚反應(yīng)中,催化效果良好。

1 實(shí)驗(yàn)部分

1.1 試劑與儀器

二乙胺、苯基異氰酸酯、對(duì)氯苯異氰酸酯、對(duì)甲基苯異氰酸酯和對(duì)甲氧基苯異氰酸酯(阿拉丁試劑公司,分析純),nBuLi(1.6 mol/L正己烷溶液,Alfa Aesar試劑公司);不對(duì)稱的碳化二亞胺PhN=C=NCy按文獻(xiàn)合成[17];實(shí)驗(yàn)中所用溶劑經(jīng)干燥、蒸餾后使用;Vario EL-Ⅲ元素測定儀,Brucker 300 MHz核磁共振波譜儀(TMS為內(nèi)標(biāo)),Bruker Smart CCD X-Ray單晶衍射儀。

1.2 合成與表征

1.2.1 [(Et)2NC(NCy)(NPh)LiOEt2]2(1)的合成與結(jié)構(gòu)表征

在氮?dú)獗Ｗo(hù)下,將n-BuLi(1.88 mL,3.0 mmol)緩慢地逐滴加到冷卻的(約0 ℃)Et2NH(0.30 mL,3.0 mmol)乙醚(約20 mL)溶液中,攪拌0.5 h,撤去冰浴,恢復(fù)到室溫后繼續(xù)反應(yīng)1 h。隨后將N-環(huán)己基-N′-苯基碳二亞胺(CyN=C=NPh,0.601 g,3.0 mmol)加入到上述的混合反應(yīng)溶液中,反應(yīng)2 h后停止攪拌,過濾,濃縮濾液至約10 mL, 將濾液放于-5℃的冰箱中,兩天后析出無色透明的晶體(1,0.923 g,87%,式1)。Anal. Calc. for C42H72LiN6O2: C, 71.36; H, 10.27; N, 11.89. Found: C, 71.20; H, 10.19; N, 12.02%.1H NMR (C6D6, δ/ppm): 0.95 (br, 6H, NCH2CH3), 1.09 (t, 6H, OCH2CH3), 1.18-1.21 (m, 4H, C6H11), 1.30-1.76 (m, 6H, C6H11), 2.95 (br, 4H, NCH2CH3), 3.13 (br, 1H, C6H11), 3.28-3.31 (q, 4H, OCH2CH3), 6.87 (t, 1H, C6H5), 6.96 (br, 2H, C6H5), 7.30 (br, 2H, C6H5);13C NMR (C6D6, δ/ppm): 13.09 (NCH2CH3), 14.97 (OCH2CH3), 26.28, 27.17, 36.34 (C6H11), 43.42 (NCH2CH3), 56.05 (C6H11), 65.29 (OCH2CH3), 122.21, 123.22, 128.65, 147.66 (C6H5), 167.53 (NCN)。

Scheme 1 Synthetic route of complex 1式1 化合物1的合成路線

1.2.2 化合物1催化異氰酸酯三聚環(huán)化合成異氰脲酸酯的一般過程

在氮?dú)獗Ｗo(hù)下將催化劑與異氰酸酯(摩爾比為0.5%)溶于約10 mL乙醚中,在室溫下逐滴加入異氰酸酯,攪拌約1 min后開始生成白色沉淀,隨著反應(yīng)進(jìn)行沉淀逐漸增多,繼續(xù)反應(yīng)10 min,停止反應(yīng)。靜置后過濾,沉淀用約10 mL乙醚洗滌2次,烘干后得到產(chǎn)品異氰脲酸酯(式2),產(chǎn)品通過NMR測試,產(chǎn)率為分離產(chǎn)率。

1,3,5-三苯基異氰脲酸酯1H NMR (CD3Cl, δ/ppm): 7.27-7.52 (m, 15H, C6H5);13C NMR (C6D6, δ/ppm): 128.87, 129.83, 134.06 (C6H5), 149.38 (C=O)。

1,3,5-三(4-甲基)苯基異氰脲酸酯1H NMR (CD3Cl, δ/ppm): 2.25 (s, 9H, CH3), 7.22-7.48 (m, 12H, C6H4);13C NMR (C6D6, δ/ppm): 20.57 (CH3), 127.37, 129.31, 130.49, 138.53 (C6H4), 148.12 (C=O)。

1,3,5-三(4-氯)苯基異氰脲酸酯1H NMR (CD3Cl, δ/ppm): 7.25-7.51 (m, 12H, C6H4);13C NMR (C6D6, δ/ppm): 129.27, 131.33, 134.92 (C6H4), 147.58 (C=O)。

1,3,5-三(4-甲氧基)苯基異氰脲酸酯1H NMR (CD3Cl, δ/ppm):1H NMR (CD3Cl, δ/ppm): 3.79 (s, 9H, OCH3), 6.95-7.33 (m, 12H, C6H4);13C NMR (C6D6, δ/ppm): 57.62 (OCH3), 116.73, 128.40, 131.57, 151.25 (C6H4), 162.00 (C=O)。

Scheme 2 Preparation of isocyanurates catalyzed by the complex 1式2 化合物1催化合成異氰脲酸酯

2 結(jié)果與討論

2.1 胍基鋰化合物1的晶體結(jié)構(gòu)

Fig.1 Molecular Structure of the guanidinatolithium complex 1 (Hydrogen atoms are omitted for clarity)圖1 胍基鋰化合物1的分子結(jié)構(gòu)(為簡潔氫原子被省略)

化合物1的晶體從乙醚溶液中結(jié)晶得到,其單晶結(jié)構(gòu)圖見圖1,部分鍵長與鍵角見表1?；衔?的分子結(jié)構(gòu)是一個(gè)二聚的鋰鹽,結(jié)構(gòu)類似于已經(jīng)報(bào)道的化合物[(iPr)2NC(NCy)2LiOEt2]2[18],呈中心對(duì)稱,對(duì)稱中心位于四邊形Li2N2的中心。化合物1分子的主體結(jié)構(gòu)類似于一個(gè)扭曲的三環(huán)梯狀結(jié)構(gòu),平面Li(1)N(3)C(7)N(1)和平面Li(1)′N(3)′C(7)′N(1)′完全平行,這兩個(gè)平面與平面Li(1)N(1)Li(1)′N(1)′形成的二面角都為60.61(8) °。分子結(jié)構(gòu)中的兩個(gè)Li原子分別同兩個(gè)胍基骨架中的三個(gè)N原子、一個(gè)O原子(來自溶劑乙醚)鍵合,形成扭曲的四面體構(gòu)型?；衔?中Li-N鍵的鍵長為1.979(3)和2.231(3)?,類似于化合物[(iPr)2NC(NCy)2LiOEt2]2中Li-N鍵的鍵長(1.987(3),2.214(3)?)。對(duì)于胍基骨架C(7)N3而言,C(7)-N(1),C(7)-N(2)和C(7)-N(3)的鍵長分別是1.332 9(18),1.398 4(18)和1.344 5(18)?,由此可見C-N鍵都具有部分雙鍵特性,三個(gè)C-N鍵具有一定程度的共軛作用。另外,Li(1)-O(1)鍵長為2.038(3),兩個(gè)金屬Li原子的距離為2.587(5)?。

表1 胍基鋰化合物1的部分鍵長(?)與鍵角(°)Table 1 Selected bond lengths (?) and bond angles (°) of the guanidinatolithium complex 1

2.2 胍基鋰化合物1催化異氰酸酯的三聚反應(yīng)

我們采用胍基鋰化合物1對(duì)芳基異氰酸酯的環(huán)化反應(yīng)進(jìn)行了研究,研究結(jié)果見表2。我們對(duì)反應(yīng)的條件進(jìn)行了優(yōu)化,首先選擇苯異氰酸酯作為底物,催化劑的加載量為0.5 mol%時(shí)進(jìn)行反應(yīng)溶劑的篩選(表2,Entries1-4),結(jié)果顯示,反應(yīng)10 min后所有苯異氰酸酯的三聚環(huán)化反應(yīng)的產(chǎn)率均能達(dá)到90%以上,但是反應(yīng)在溶劑乙醚中的產(chǎn)率最高,苯基異氰脲酸酯的產(chǎn)率能達(dá)到98%;其次在催化劑加載量和反應(yīng)溶劑不變的情況下,我們改變苯異氰酸酯三聚環(huán)化的反應(yīng)時(shí)間發(fā)現(xiàn),縮短和延長反應(yīng)時(shí)間,對(duì)苯基異氰脲酸酯的產(chǎn)率影響不大(表2,Entries 5-6);當(dāng)催化劑的加載量減半后,苯異氰酸酯的三聚環(huán)化反應(yīng)的產(chǎn)率略有減少(表2,Entry 7)。因此使用胍基鋰化合物1進(jìn)行催化芳基異氰酸酯三聚環(huán)化反應(yīng)的最佳條件為:常溫下在乙醚溶劑中,催化劑的加載量為0.5 mol%,反應(yīng)時(shí)間為10 min。另外,我們使用胍基鋰化合物1在最佳的反應(yīng)條件下,拓展了底物的范圍(表2,Entries 8-10)。研究發(fā)現(xiàn),芳基異氰酸酯中芳環(huán)上取代基對(duì)其三聚環(huán)化產(chǎn)率有一定的影響,當(dāng)苯環(huán)對(duì)位上是給電子基團(tuán)時(shí),轉(zhuǎn)化產(chǎn)率降低,苯環(huán)對(duì)位上是吸電子基團(tuán)時(shí),轉(zhuǎn)化產(chǎn)率明顯升高。究其原因是,轉(zhuǎn)化產(chǎn)率和異氰酸根中碳原子的電子云密度有關(guān)[19],苯環(huán)上給電子基團(tuán)使碳原子的電子云密度增加,苯環(huán)上吸電子基團(tuán)使碳原子的電子云密度降低。

表2 胍基鋰化合物1催化異氰酸酯三聚反應(yīng)Table 2 Trimerization of isocyanates catalyzed by the guanidinatolithium complex 1

3 結(jié)論

合成了一個(gè)新的胍基鋰化合物,并且利用NMR、X-ray單晶衍射等測試手段對(duì)該化合物進(jìn)行了完整的結(jié)構(gòu)表征,另外使用該化合物對(duì)異氰酸酯的三聚反應(yīng)進(jìn)行了研究。研究表明,底物芳基異氰酸酯中芳環(huán)上取代基的種類對(duì)反應(yīng)的產(chǎn)率有一定的影響,芳環(huán)上吸電子基團(tuán)有利于異氰酸酯的三聚反應(yīng)。

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Synthesis,CrystalStructureandItsApplicationinTrimerizationofIsocyanatesofaGuanidinatolithiumComplex

GAO Xiaona1,2,HAN Hongfei2,GUO Zhiqiang3,WEI Xuehong2,3*

(1.DepartmentofAppliedChemistry,YunchengUniversity,Yuncheng044000,China;2.SchoolofChemistryandChemicalEngineering,ShanxiUniversity,Taiyuan030006,China;3.ScientificInstrumentCenter,ShanxiUniversity,Taiyuan030006,China)

Treatment of diethyl amide with n-butyl lithium and unsymmetric carbodiimine PhN=C=NCy afforded a new guanidinatolithium complex, [(Et)2NC(NCy)(NPh)LiOEt2]2(1), which was characterized by elemental analyses,1H,13C NMR spectra and single crystal X-ray diffraction analysis. In addition, the trimerization of aryl isocyanates to aryl isocyanurates catalyzed by the guanidinatolithium complex (1) was also investigated. The experimental results showed that the yield of aryl isocyanurate by the trimerization reaction was up to 99% when mol ratio of1as pre-catalyst to substrate is 0.5%,and reaction time is for 10 min at room temperature.

guanidinatolithium complex;synthesis;crystal structure;catalysis

10.13451/j.cnki.shanxi.univ(nat.sci.).2017.04.028

2017-03-31；

2017-04-19

山西省煤基重點(diǎn)科技攻關(guān)項(xiàng)目(MH2014-07),山西省自然科學(xué)基金(201601D202091)

高曉娜(1987-),女,助教,主要研究方向:金屬有機(jī)合成。E-mail:771984363@qq.com

*通信作者：魏學(xué)紅(WEI Xuehong),E-mail:xhwei@sxu.edu.cn

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A

0253-2395(2017)04-0854-05