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Synthesis, Chemical and Catalytic Properties of Transition Metal Complexes with Polydentate Phosphine Ligands
http://ir.ncue.edu.tw/ir/handle/987654321/18950
title: Synthesis, Chemical and Catalytic Properties of Transition Metal Complexes with Polydentate Phosphine Ligands abstract: The linear chiral triphosphine ligand (S,S)-PhP(CH2C*HMeCH2PPh2)2, ttp*, was synthesized by the reaction of (S)-Ph2PCH2CHMeCH2Cl and PhPH2 in the presence of LDA. Treatment of [RhCl(COD)]2 with ttp* produced RhCl(ttp*). Reaction of RuCl2(PPh3)3 or RuCl2(DMSO)4 with ttp* gave RuCl,(ttp*). Reaction of CoCl2 with ttp* in methanol gave CoCl2(ttp*). Treatment of RhCl(ttp*) and RuCl2(ttp*) with NaBH4 led to Rh(BH4)(ttp*) and RuH(η2-BH4)(ttp*) respectively. The tripodal chiral triphosphine ligand (R)-Ph2PCH2CH(PPh2)CH2CH2PPh2, etp* was synthesized by the reaction of (S)-MsOCH2CH(OMs)CH2CH2OMs with KPPh2. Reaction of RuCl2(DMSO)4 and etp* gave RuCl(etp*). A series of ruthenium complexes with the orthometallated ligand [2,6- (PhP2CH2)2C6H3]- (PCP) were synthesized. Reaction of RuCl2(PPh3)3 with 1,3-(Ph2PCH2)2C6H4 produced the coordinatively unsaturated complex RuCl(PPh3)(PCP), which was characterized by X-ray crystallography. Treatment of RuCl(PPh3)(PCP) with 4-phenylpyridine (pyph) yielded RuCl(pyph)(PPh3)(PCP). Treatment of RuCl(PPh3)(PCP) with PMe3 and CO generated RuCl(PMe3)2(PCP) and RuCl(CO)2(PCP), respectively. Reactions of RuCl(PPh3)(PCP) with NaH in THF and NaBH4 in methanol gave RuH(PPh3)(PCP) and RuH(CO)(PPh3)(PCP), respectively. The hydride complex RuH(PMe3)2(PCP) was prepared by the reaction of RuCl(PMe3)2(PCP) with NaBH4. Reaction of RuCl(PPh3)(PCP) with NaBH4 in THF produced an orange compound which can be formulated as a BH3 complex RuH(BH3)(PPh3)(PCP) (A). RuH(BH3)(PPh3)(PCP) (A) isomerized to RuH(BH3)(PPh3)(PCP) (B) in solution. Treatment of RuH(BH3)(PPh3)(PCP) (A) with CO produced a mixture of RuH(CO)(PPh3)(PCP) and RuH(CO)2(PCP). Reaction of RuH(BH3)(PPh3)(PCP) (A) with PMe3 gave RuH(PMe3)(PPh3)(PCP). Treatment of RuH(BH3)(PPh3)(PCP) (B) with CO and PMe3 led to RuH(CO)(PPh3)(PCP) and RuH(PMe3)(PPh3)(PCP) respectively. Reactions of RuCl(PPh3)(PCP) (PCP = 2,6-(PPh2CH2)2C6H3) with PhC[is equivalent to]CH and HC[is equivalent to]CC(OH)Ph2 gave the unusual coupling products RuCl(PPh3)(η4-PhCH=C-2,6-(PPh2CH2)2C6H3) and RuCl(PPh3)(η4- Ph2C(OH)CH=C-2,6-(PPh2CH2)2C6H3), respectively. RuCl(PPh3)(η4-PhCH=C-2,6-( PPh2CH2)2C6H3) was characterized by X-ray crystallography. Dehydration was observed in the coupling reactions of RuCl(PPh3)(PCP) with HC[is equivalent to]CC(OH)PhMe and HC[is equivalent to]C-cyclo-C6H10(OH). Thus the coupling products RuCl(PPh3)(η4-CH2=CPhCH=C-2,6-(PPh2CH2)2C6H3) and RuCl(PPh3)(η4-cyclo-C6H9-CH=C-2,6-(PPh2CH2)2C6H3) were obtained from the reactions of RuCl(PPh3)(PCP) with HC[is equivalent to]CC(OH)PhMe and HC[is equivalent to]C-cyclo-C6H10( OH), respectively. Treatment of [Ru(PMe3)2(PCP)]BF4 with PhC[is equivalent to]CH produced [Ru(PMe3)2(η4-PhCH=C-2,6-(PPh2CH2)2C6H3)]BF4. Reaction of RuCl(PPh3)(PCP) with PhC[is equivalent to]CLi gave Ru(C[is equivalent to]CPh)(PPh3)(PCP). Protonation of this acetylide complex in the presence of Cl- produced the coupling product RuCl(PPh3)(η4-PhCH=C-2,6-(PPh2CH2)2C6H3) along with some uncharacterized species. Treatment of RuCl2(PPh3)3 with PMP (PMP=2,6-(Ph2PCH2)2C5H3N) in acetone produced RuCl2(PPh3)(PMP) which has been characterized by X-ray diffraction. Treatment of RuCl2(PPh3)(PMP) with NaBH4 in methanol gave RuHCl(PPh3)(PMP), acidification of which with HBF4.Et2O produced the molecular dihydrogen complex [RuCl(H2)(PPh3)(PMP)]BF4. Treatment of RuHCl(CO)(PPh3)3 with PMP in benzene produced RuHCl(CO)(PMP) which reacted with HBF4.Et2O to give the molecular dihydrogen complex [RuCl(H2)(CO)(PMP)]BF4. The osmium molecular dihydrogen complex [OsCl(H2)(PPh3)(PMP)]BF4 was prepared by protonation of OsHCl(PPh3)(PMP) with HBF4.Et2O. Relative acidities of the dihydrogen complexes were investigated by NMR spectroscopy of equilibration reactions conducted in CD2Cl2.[RuCl(H2)(CO)(PMP)]BF4 is more acidic than [RuCl(H2)(PPh3)(PMP)]BF4 which is in turn more acidic than its osmium analog [OsCl(H2)(PPh3)(PMP)]BF4. The catalytic properties of RuH(η2-BH4)(ttp), RuCl2(ttp), RhCl(ttp*), RuCl(PPh3)(PCP) and RuCl2(PPh3)(PMP) for hydrogenation of styrene have been tested. RuH(η2-BH4)(ttp) and RuCl(PPh3)(PCP) are very efficient catalysts and quantitative yield of ethylbenzene was obtained in 20 min. RuCl2(PPh3)(PMP) has a relatively poor activity. The catalytic properties of RuCl2(ttp*), RhCl(ttp*), Rh(BH4)(ttp*), RuH(η2-BH4)(ttp*) and RuCl2(etp*) for the asymmetric hydrogenation of α-acetamidocinnamic acid have been tested. RuCl2(ttp*), RhCl(ttp*), Rh(BH4)(ttp*) and RuH(η2-BH4)(ttp*) are efficient catalysts and quantitative production of N-acetyl-(S)-phenylalanine could be obtained after 24 hrs. However, the optical yield is moderate and in the range of 2-50%. The catalytic properties of RuCl2(ttp*), RuCl2(etp*), RuCl2(pigiphos), RuCl2(PPh3)3 and RuCl(PPh3)(PCP) for cyclopropanation were investigated using styrene and ethyl diazoacetate as the substrates. The yields for cyclopropanation products are relatively low and the major products are diethyl fumarate and diethyl maleate. The cis/trans ratio for the cyclopropanation product is moderate and the optical yields for the reactions are low. Reaction of RuCl2(ttp*) with ethyl diazoacetate produced RuCl2(ttp*)(=CHCO2Et), which in reactions with ethyl diazoacetate and styrene produced the dimerization and cyclopropanation products respectively.
<br>Oxidative Dimerization of Methane Over Sodium-Promoted Calcium Oxides
http://ir.ncue.edu.tw/ir/handle/987654321/16855
title: Oxidative Dimerization of Methane Over Sodium-Promoted Calcium Oxides abstract: Sodium-promoted calcium oxides are active and selective catalysts for the partial oxidation of methane to ethane and ethylene using molecular oxygen as an oxidant. In a conventional fixed-bed flow reactor, operating at atmospheric pressure, a 45% C2 (sum of ethane and ethylene) selectivity was achieved to a 33% methane conversion over 2.0 g of the catalyst at 725°C with a gas mixture of CH4/O2 = 2. The other products were CO and CO2. EPR results indicate that [Na+O-] centers in Na/CaO are responsible for the catalytic production of CH3 from methane through hydrogen-atom abstraction. These CH3 radicals dimerize, primarily in the gas-phase, to form C2H6 which further oxidizes to C2H4. Increasing temperatures reverse the gas-phase equilibrium CH3+O2 ⇌ CH3O2 to produce more CH3 and increase the C2 selectivity. The CH3O2 eventually is converted to carbon oxides under the reaction conditions employed, therefore increasing O2 pressures decrease the C2 selectivity. There is evidence that CH3O2 in the presence of C2H6 initiates a chain reaction which enhances the methane conversion. The addition of Na to CaO also reduces the surface area of the catalysts, thus minimizing a nonselective oxidation pathway via surface methoxide intermediates.
<br>The Role of [M+O-] Centers (M+=Group IA Ion) in the Activation of Methane on Metal Oxides
http://ir.ncue.edu.tw/ir/handle/987654321/16854
title: The Role of [M+O-] Centers (M+=Group IA Ion) in the Activation of Methane on Metal Oxides abstract: If the ionic radii are compatible, alkali metal ions will substitute for the divalent metal ions in magnesium oxide, calcium oxide and zinc oxide. At high temperatures in the presence of molecular oxygen, centers of the type [M+O−] are formed, where MM+– Group IA ion. The O− ions in equilibrium with these centers are effective in H” abstraction from CH4, which is the first step in the oxidative dimerization reaction. At reaction temperatures >720°C alkali metal oxides formed on the catalytic surface may themselves become active centers. Alkali metal carbonates also may inhibit the activity of the host oxide and sinter the oxide, thereby eliminating corner sites which result in complete oxidation.
<br>有機分子與有機奈米粒子在溶液中之飛秒螢光動力學研究
http://ir.ncue.edu.tw/ir/handle/987654321/15473
title: 有機分子與有機奈米粒子在溶液中之飛秒螢光動力學研究 abstract: 在本篇論文中,我們利用時間解析螢光光譜對於有機奈米粒子(PPB) 和有機奈米帶 (CNDSB) 的激發態動力學以及螢光增益現象作一深入的探討。在水和THF的混合溶液中,我們藉由控制水和THF比例生成不同大小的奈米粒子。研究結果顯示,在PPB奈米粒子中的螢光增益效應主要是由於在奈米粒子中分子的平面化以及在聚集體(aggregate)中分子和分子間的交互作用所造成。我們利用時間解析螢光光譜以及粉末X光繞射 (powder XRD)的量測,發現在PPB奈米粒子中,其晶體的排列具有兩種不同的構型。對於CNDSB 分子,藉由比較CNDSB 在THF和PMMA薄膜中的時間解析螢光光譜,我們發現在結構上的限制僅能造成部分的螢光增益效應。然而在CNDSB 奈米帶中,我們觀測到一十分有趣的超快能量傳遞過程,其時間小於150 飛秒。由於在PPB奈米粒子中,我們並沒觀測到此一現象,因此我們認為此一超快的能量傳遞過程應該由於CNDSB的一維奈米結構所造成,而其反映了能量在奈米帶的長軸方向的傳遞速度。
在第二部份的研究方面,我們針對了一新合成的咔唑(carbazole) 衍生物: BMVC,分別對其在有機溶劑中以及DNA錯合物中的激發態及水合動力學做一探討。當BMVC溶解於tris-buffer (PH=7.5)時,其激發態的緩解主要是經由C=C雙鍵旋轉所造成的內轉換(internal conversion) 或是C-C單鍵旋轉所造成的系統間跨越(intersystem crossing)。也因此當我們將BMVC 溶解在甘油(glycerol)時,由於分子的轉動受到了限制,其螢光強度以及生命期均大幅的增加。在水合動力學(solvation dynamics)方面,在甘油中由於分子的高黏滯性,因此使得水合時間大幅度的減緩。而當BMVC雙股螺旋(duplex)及四股螺旋(quadruplex) DNA作用時,由於BMVC 和DNA間的作用限制了分子內運動,因此其螢光強度和在甘油中一樣均有大幅度的增加。藉由水合動力學的測量,我們認為在DNA表面的水可分為兩種,其中之一是屬於自由的水分子,而另一種則屬於和表面有部份結合的水分子。藉由分析此兩種水分子的水合時間,我們認為BMVC在雙股螺旋DNA中的結合位置是位於大溝(major groove)以及小溝(minor groove)之間。而當BMVC 和四股螺旋DNA結合時,其水合作用中和表面有部份結合水分子所佔的比例和BMVC在雙股螺旋DNA中相較有顯著的增加。因此我們認為在四股螺旋中BMVC是更加深埋在DNA分子之中。
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