【正文】 ) are also asymmetric, differing by almost A 176。 . Two THF molecules plete the coordination sphere of aluminum with AlObond lengths of (1) and (1) A 176。 direct analogues appear to be absent from the literature, but related examples in which the LiH participates in threecentertwoelectron bonding arrangements with other metals are A plausible sequence for the production of products 1 and 2 is shown in Scheme 1. The reaction likely proceeds through initial salt metathesis to form a scandium borohydride intermediate akin to II as observed by Mindiola et Since II is an isolable species, it is likely that liberation of BEt3 is facile in the present system。 . Each scandium adopts a distorted trigonalbipyramidal geometry, with the encapsulated hydride and oxygen from THF occupying the apical positions. The hydride was crystallographically located and is symmetrically bound to the three scandium centers with an average ScH bond length of (2) A 176。 removal by treatment with a Lewis base could potentially liberate a reactive scandium hydride. Indeed, this was apparently observed by Fryzuk et al. in the reaction of a PNP pincer ligand stabilized scandium borohydride with PMe3, although the chemistry was not clean enough to allow for exploration of the chemistry of the resulting scandium 英文文獻(xiàn) II Furthermore, Mindiola et al. have demonstrated that BEt3 is labile in the plex II, prepared via reaction of LSc(NHAr)Cl (Ar = 2,6diisopropylphenyl) with NaHBEt3, liberating a putative ScH species, which was trapped with a series of oxygencontaining With these precedents in mind, we report the reactions of the welldefined, monomeric, and basefree scandium dichloride precursor to dialkyls I, in which the naac ligand bears tertbutyl substituents, with the boro and aluminohydride reagents LiHBEt3 and LiAlH4. These studies show that this naac ligand framework does not support scandium hydrides but undergoes fragmentation to yield imidecontaining clusters. Results and Discussion Clean reaction of the βdiketiminato scandium dichloride (LScCl2) depicted in Scheme 1 with LiBEt3H occurs when carried out with equiv of the borohydride reagent in toluene over the course of 12 h, yielding the scandiumcontaining product 1 and the anic eneamine 2. Initial experiments utilized equimolar amounts of LScCl2 and LiBEt3H led to more plex product mixtures from which the unusual cluster 1 was isolated and characterized by Xray crystallography (see below). The occluded LiH evident in this structure, present in a 1/3 ratio with scandium, suggested that its clean production required an extra equiv of LiBEt3H, which was experimentally borne out in subsequent preparations. The eneamine product 2 arises from the βdiketiminate scaffold and was identified by GC/MS (m/z = 327 g/mol) and 1H NMR spectroscopy. Characteristic resonances in C6D6 include a wellresolved AB quartet centered at ppm corresponding to the transcoupled olefinic protons (3JHH = Hz) and two signals at and ppm for the inequivalent tBu groups. Loss of this fragment necessarily leaves “ArNdScCl”, which apparently assembles into the trinuclear cluster 1, templated around LiH and stabilized by THF molecules present since LiBEt3H is administered as a M solution in THF. Product 1 is isolated by precipitation and washing with cold pentane。 最后，向在百忙中抽出時(shí)間對本 文進(jìn)行答辯并提出寶貴意見的各位老師表示衷心地感謝！ 英文文獻(xiàn) I 英文文獻(xiàn) Nucleophilic Degradation of a βDiketiminato Ancillary by a Transient Scandium Hydride Intermediate Reactions of a βdiketiminatosupported scandium dichloride LScCl2(L = (Ar)NC(tBu)CHC(tBu)N(Ar)。 感謝父母的養(yǎng)育之恩，天高地厚無以為報(bào)，我只能更加努力的學(xué)習(xí)，期望能給他們帶來更多的安慰。有機(jī)相 P204 加入后， Sc 的提取率大幅度下降 ； P507 加入后， P507 的量與提取率大概成線性降低的關(guān)系 ； 仲辛醇加入后，對鈧的萃取有抑制作用， 顯色峰位置 不變，仲辛醇對其他元素的萃取比較 能力弱，但不適合酸性的酸洗條件。 在高酸度下，偶氮胂（ Ⅲ ）法能準(zhǔn)確測定出微量鈧。 實(shí)驗(yàn)過程中發(fā)現(xiàn)，反萃液 pH 值為負(fù)值，具體實(shí)驗(yàn)結(jié)果見表 、圖、圖 。 表 P507 的含量對協(xié)同萃取的影響 實(shí)驗(yàn)編號 TBP(ml) P507(ml) λ(nm) Abs 反萃液中的鈧含量（ ug/ml） 1 3 0 676 2 3 1 652 3 3 2 652 4 3 3 652 5 3 6 653 表 ICPMAS 測定 2 號反萃液中主要元素及含量（ ppb） 元素 Sc Ga Y La Ce Pr Nd 反萃液含量 第 3 章 實(shí)驗(yàn)結(jié)果與討論 22 400 500 600 700 800 900 0 . 0 50 . 0 00 . 0 50 . 1 00 . 1 50 . 2 00 . 2 50 . 3 00 . 3 50 . 4 00 . 4 50 . 5 00 . 5 5 4321 Absλ ( nm) 圖 不同 P507 含量的吸光光譜 0 1 2 3 4 5 6203040506070 提取率(%)P 5 0 7 的量( m l ) 圖 P507 的量與提取率的關(guān)系 第 3 章 實(shí)驗(yàn)結(jié)果與討論 23 TBP+仲辛醇（煤油）協(xié)同萃取體系 實(shí)驗(yàn)步驟詳見 鈧的萃取方法，需要在萃取步驟中加入?yún)f(xié)同萃取劑。具體實(shí)驗(yàn)結(jié)果見表 、 表 、 圖 、圖 。具體步驟如下：將 3mlTBP， 1mlP507（變量）和 26ml 煤油（變量）加入分液漏斗中，再加入 10ml 精制液，用力搖晃 3 分鐘，大概平均每秒進(jìn)行兩次，搖勻后，放分液漏斗架上靜置 15 分鐘。 ICP 的測試結(jié)果 詳見（圖 ） 也表明鈧的萃取效果不好，提取率僅為 %， 鈧在反萃液中沒有被萃取出來，說明 P204 對鈧的吸附能力比較強(qiáng)。調(diào)節(jié) pH 值的方法改為指示劑法：移取8ml 反萃液，滴入一滴甲基橙，逐滴加入氫氧化鈉使溶液變黃，之后再加鹽酸，使黃色褪去變橘黃色或者橙色。 表 相比對鈧的提取效果的影響 實(shí)驗(yàn)編號 1 2 3 4 萃取相比 3:1 2:1 1:1 1:2 λ(nm) 675 674 674 673 Abs 反萃液中的鈧含量（ ug/ml） 第 3 章 實(shí)驗(yàn)結(jié)果與討論 16 400 500 600 700 800 900 1:21:12:13:1 Absλ (nm) 圖 不同相比的吸光光譜 101520253035404550556065707580851 ： 21 ： 12 ： 1 3 ： 1提取率(%)萃取相比 圖 萃取相比與 Sc 提取率的關(guān)系 第 3 章 實(shí)驗(yàn)結(jié)果與討論 17 表 TBP 含量對鈧的提取效果的影響 實(shí)驗(yàn)編號 TBP 含量 λ(nm) Abs 反萃液中的鈧含量 （ ug/ml） 1 50% 676 2 10% 676 400 500 600 700 800 9000 . 250 . 200 . 150 . 100 . 050. 000. 050. 100. 150. 200. 250. 300. 350. 4050%10%Absλ /nm 圖 50%TBP 的吸光光譜 協(xié)同萃取體系對 Sc 的提取效果 在上面的實(shí)驗(yàn)過程中發(fā)現(xiàn)，有機(jī)相的量會(huì)對鈧的提取率產(chǎn)生影響，根據(jù)其他稀土元素，如鎵等元素的萃取方法與機(jī)理，想到可不可以用協(xié)同萃取體系對鈧進(jìn)行萃取，本實(shí)驗(yàn)選用三種常用協(xié)同萃取劑， P204， P507，仲辛醇進(jìn)行實(shí)驗(yàn)研究。具體實(shí)驗(yàn)結(jié)果如表 、圖 、圖 所示。說明酸洗時(shí)間對鈧的提取率的影響不是很大，因?yàn)樗岬臐舛群艽?，高濃度酸性條件洗滌液體具有較差的融合性，鈧的流失量就很少。 表 HCl 濃度對鈧的提取效果的影響 樣品編號 酸洗濃度 (mol/l) 峰位 (nm) Abs 反萃液中的鈧含量 （ ug/ml） 1