Coordination and organometallic chemistry of relevance to the rhodium-based catalyst for ethylene hydroamination

The RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI catalytic system for the hydroamination of ethylene by aniline is shown to be thermally stable by a recycle experiment and by a kinetic profile study. The hypothesis of the reduction under catalytic conditions to a Rh(I) species is supported by the observation of a high catalytic activity for complex [RhI(PPh(3))(2)](2). New solution equilibrium studies on [RhX(PPh(3))(2)](2) (X = Cl, I) in the presence of ligands of relevance to the catalytic reaction (PPh(3), C(2)H(4), PhNH(2), X(-), and the model Et(2)NH amine) are reported. Complex [RhCl(PPh(3))(2)](2) shows broadening of the (31)P NMR signal upon addition of PhNH(2), indicating rapid equilibrium with a less thermodynamically stable adduct. The reaction with Et(2)NH gives extensive conversion into cis-RhCl(PPh(3))(2)(NHEt(2)), which is however in equilibrium with the starting material and free Et(2)NH. Excess NHEt(2) yields a H-bonded adduct cis-RhCl(PPh(3))(2)(Et(2)NH)···NHEt(2), in equilibrium with the precursors, as shown by IR spectroscopy. The iodide analogue [RhI(PPh(3))(2)](2) shows less pronounced reactions (no change with PhNH(2), less extensive addition of Et(2)NH with formation of cis-RhI(PPh(3))(2)(NHEt(2)), less extensive reaction of the latter with additional Et(2)NH to yield cis-RhI(PPh(3))(2)(Et(2)NH)···NHEt(2). The two [RhX(PPh(3))(2)](2) compounds do not show any evidence for addition of the corresponding X(-) to yield a putative [RhX(2)(PPh(3))(2)](-) adduct. The product of C(2)H(4) addition to [RhI(PPh(3))(2)](2), trans-RhI(PPh(3))(2)(C(2)H(4)), has been characterized in solution. Treatment of the RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI/PhNH(2) mixture under catalytic conditions yields mostly [RhCl(PPh(3))(2)](2), and no significant halide exchange, demonstrating that the promoting effect of iodide must take place at the level of high energy catalytic intermediates. The equilibria have also been investigated at the computational level by DFT with treatment at the full QM level including solvation effects. The calculations confirm that the bridge splitting reaction is slightly less favorable for the iodido derivative. Overall, the study confirms the active role of rhodium(I) species in ethylene hydroamination catalyzed by RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI and suggest that the catalyst resting state is [RhCl(PPh(3))(2)](2) or its C(2)H(4) adduct, RhCl(PPh(3))(2)(C(2)H(4)), under high ethylene pressure.     

Mechanism of beta-hydrogen elimination from square planar iridium(I) alkoxide complexes with labile dative ligands

Mechanistic studies were conducted on beta-hydrogen elimination from complexes of the general formula [Ir(CO)(PPh(3))(2)(OR)], which are square planar alkoxo complexes with labile ligands. The dependence of rate, isotope effect, and alkoxide racemization on phosphine concentration revealed unusually detailed information on the reaction pathway. The alkoxo complexes were remarkably stable, including those with a variety of electronically and sterically distinct groups at the beta-carbon. These complexes were much more stable than the corresponding alkyl complexes. Thermolysis of these complexes in the presence of PPh(3) yielded the iridium hydride [Ir(CO)(PPh(3))(3)H] and the corresponding aldehyde or ketone with rate constants that were affected little by the groups at the beta-carbon. The reactions were first order in iridium complexes. At low [PPh(3)], the reaction rate was nearly zero order in PPh(3), but reactions at high [PPh(3)] revealed an inverse dependence of reaction rate on PPh(3). The rate constants were similar in toluene, THF, and chlorobenzene. The y-intercept of a 1/k(obs) vs [PPh(3)] plot displayed a primary isotope effect, indicating that the y-intercept did not simply correspond to phosphine dissociation. These data and a dependence of alkoxide racemization on [PPh(3)] showed that the elementary beta-hydrogen elimination step was reversible. A mechanism involving reversible beta-hydrogen elimination followed by associative displacement of the coordinated ketone or aldehyde by PPh(3) was consistent with all of our data. This mechanism stands in contrast with the pathways proposed recently for alkoxide beta-hydrogen elimination involving direct elimination, protic catalysts, or binuclear mechanisms and shows that alkoxide elimination can follow pathways similar to those for beta-hydrogen elimination from alkyl complexes.     

琥珀酸酐均相加氢制备γ-丁内酯的研究

研究了不同催化剂对琥珀酸酐加氢生成γ -丁内酯的反应 ,并考察了配体、溶剂及PPh3/Ru摩尔比对催化反应的影响。结果发现Ru络合物是最佳催化剂 ,PPh3是最佳配体 ,乙二醇二甲醚为最佳溶剂。在SA ,2 0mmol;催化剂Ru ,0 .10mmol;PPh3/Ru ,8;以乙二醇二甲醚为溶剂( 8ml) ;H2 ,3.0MPa ;反应温度为 12 0℃的反应条件下 ,γ -丁内酯的产率可达 86.5%。     

Syntheses, structural determinations of [Ru(ROCS2)2(PPh3)2](+/0) pairs, and kinetic analyses of thermal reactions involving transient trans-[Ru(iPrOCS2)2(PPh3)2] species (ROCS2(-) = ethyl- or isopropyldithiocarbonate and PPh3 = triphenylphosphine)

Controlled-potential electrochemical oxidation of cis-[Ru(ROCS2)2(PPh3)2] (R = Et, iPr) yielded corresponding Ru(III) complexes, and the crystal structures of cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2](PF6) were determined. Both pairs of complexes exhibited almost identical coordination structures. The Ru-P distances in trans-[Ru(III)(ROCS2)2(PPh3)2](PF6) [2.436(3)-2.443(3) A] were significantly longer than those in cis-[Ru(II)(ROCS2)2(PPh3)2] [2.306(1)-2.315(2) A]: the smaller ionic radius of Ru(III) than that of Ru(II) stabilizes the trans conformation for the Ru(III) complex due to the steric requirement of bulky phosphine ligands while mutual trans influence by the phosphine ligands induces significant elongation of the Ru(III)-P bonds. Cyclic voltammograms of the cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2]+ complexes in dichloromethane solution exhibited typical dual redox signals corresponding to the cis-[Ru(ROCS2)2(PPh3)2](+/0) (ca. +0.15 and +0.10 V vs ferrocenium/ferrocene couple for R = Et and iPr, respectively) and to trans-[Ru(ROCS2)2(PPh3)2](+/0) (-0.05 and -0.15 V vs ferrocenium/ferrocene for R = Et and iPr, respectively) couples. Analyses on the basis of the Nicholson and Shain's method revealed that the thermal disappearance rate of transient trans-[Ru(ROCS2)2(PPh3)2] was dependent on the concentration of PPh3 in the bulk: the rate constant for the intramolecular isomerization reaction of trans-[Ru(iPrOCS2)2(PPh3)2] was determined as 0.338 +/- 0.004 s(-1) at 298.3 K (deltaH* = 41.8 +/- 1.5 kJ mol(-1) and deltaS* = -114 +/- 7 J mol(-1) K(-1)), while the dissociation rate constant of coordinated PPh3 from the trans-[Ru(iPrOCS2)2(PPh3)2] species was estimated as 0.113 +/- 0.008 s(-1) at 298.3 K (deltaH* = 97.6 +/- 0.8 kJ mol(-1) and deltaS* = 64 +/- 3 J mol(-1) K(-1)), by monitoring the EC reaction (electrode reaction followed by chemical processes) at different concentrations of PPh3 in the bulk. It was found that the trans to cis isomerization reaction takes place via the partial dissociation of iPrOCS2(-) from Ru(II), contrary to the previous claim that it takes place by the twist mechanism.     

铑配合物催化丁烯氢甲酰化性能的研究

制备了一系列铑配合物,并对其催化丁烯氢甲酰化的催化性能进行了研究.在1-丁烯的反应中,RhCl(PPh3)3和trans-RhCl(CO)(PPh3)2的反应速度很慢,而RhH(CO)(PPh3)3、Rh(CO)2(acac)和 Rh(CO)(acac)(PPh3)三者反应速度都很快.而不同丁烯原料氢甲酰化的反应速度也各不相同,反应速度依次为1-丁烯》2-丁烯》异丁烯.     

PPh3-catalyzed synthesis of dicyano-2-methylenebut-3-enoates as efficient dienes in catalytic asymmetric inverse-electron-demand Diels-Alder reaction

We present here the synthesis of dicyano-2-methylenebut-3-enoates as novel Diels-Alder dienes through an efficient PPh(3)-catalyzed strategy, and an unprecedented PPh(3)-catalyzed addition/all-carbon-based asymmetric inverse-electron-demand Diels-Alder sequence reaction is disclosed for the first time.     

The photolysis of Chlorocarbonylbis(triphenylphosphine)iridium(I) in chloroform

Under 254 or 313 nm irradiation in chloroform, [IrCl(CO)(PPh3)2] is converted cleanly to [IrCl2(CO)H(PPh3)2] through the addition of HCl, produced photochemically. Under 254 nm irradiation, some of the reaction of [IrCl(CO)(PPh3)2] occurs by direct photolysis of chloroform, though a greater contribution arises from a reaction initiated through absorption of light by the metal complex. Under 313 nm irradiation, essentially all of the reaction is metal-initiated. The linear dependence of the reaction rate on light intensity and on the fraction of light absorbed by the Ir(I) complex as well as the lack of a deuterium isotope effect rule out a radical process. Instead it is proposed that an association complex between excited state [IrCl(CO)(PPh3)2] and CHCl3 leads to dissociation of a chlorine atom from CHCl3, yielding HCl after abstraction of a hydrogen from another CHCl3. HCl then adds to a ground state [IrCl(CO)(PPh3)2] complex.     

Study on the Deactivation Kinetics of Pd（PPh3）2Cl2 in the Monocarbonylation of Benzyl Chloride

The deactivation kinetics of Pd(PPh3)2Cl2 in the monocarbonylation of benzyl chloride to synthesize phenylacetic acid is studied in this paper. Solid 1-(2-pyridylazo)-2-naphthol (PAN) is used as the colouring agent, and the concentration of Pd(PPh3)2Cl2 in the system is measured through absorptiometry. The result shows that the optimum condition of the chromogenic reaction between Pd2+ and PAN is: 0.5 ml of 0.04% PAN added to 10 ml of Pd2+ solution (1.0×10-6-2.0×10-5 mol/L), and heated in a constant temperature water bath at 40℃ for about 30 min, with pH of the solution being about 3.0. The molar coefficient of absorption is 1.384×104 L/(mol·cm); the orders of the hydrolytic reaction to the concentration of Pd(PPh3)2Cl2, PPh3, phenylacetic acid and NaOH are 0.5, minus 0.8, 2 and 1.2, respectively. The activation energy (E) of the hydrolytic reaction is 75.59 kJ/mol, and the pre-exponential factor is 1.68×1012.     

配合Pd催化剂薄荷醇与异丁烯羰基合成Validol

用PdCL2(PPh3)2/PPh3/P-CH3C6H4SO3H复合催化体系,在间歇高压釡中,以二甲苯为溶剂,在一定的反应温度、CO/H2压力和薄荷醇与异丁烯浓度下,研究了主催化剂浓度和各种助催化剂的配比对薄荷醇转化率和反应速度的影响.在适宜的催化体系和反应体系中,进行了反应物的转化率、Validol的选择性和收率与反应时间关系实验.对98%以上Validol产物进行了FT-TR、MS、13C NMR和1H NMR鉴别.最后,完成了反应温度、CO压力和薄荷醇、异丁烯浓度对羰基合成Validol反应速度的影响实验,提出了该反应的反应机理和催化循环过程.     

基于黄酮的ESIPT型荧光探针检测三苯基膦

三苯基膦(PPh3)是一种重要的有机化合物,具有亲核性和还原性,已被广泛用于有机合成和有机金属化合物配位中。然而PPh3的过量使用不可避免地会引起环境的污染,并且对人体的健康也具有潜在威胁。因此我们迫切需要一种方便而高效的检测PPh3的方法。已有检测方法在便捷性和灵敏性等方面不如人意,而小分子荧光探针因其灵敏度高、选择性好、检测简单等优点受到广泛关注。受生物标记领域常用的无痕Staudinger连接反应的启发,本文设计合成了一个类似Staudinger连接反应,以能够具有固态发光性质的激发态分子内质子转移(ESIPT)特性的3-羟基黄酮荧光染料为母核,以邻叠氮苯乙酸酯为识别基团,用于检测PPh3的荧光增强型的探针分子。通过叠氮与PPh3反应,经过氮杂叶立德中间体,进行快速的分子内酰胺化,释放3-羟基黄酮染料并恢复荧光发射,从而实现在溶液中及滤纸上快速检测PPh3的目的。该探针在定量和定性检测PPh3方面具有潜在应用价值。     

A bis(phosphinimino)methanide lanthanum amide as catalyst for the hydroamination/cyclisation, hydrosilylation and sequential hydroamination/hydrosilylation catalysis

[La[N(SiHMe2)2]2[CH(PPh2NSiMe3)2]], which was obtained via an amine elimination starting from [CH2(PPh2NSiMe3)2] and [La[N(SiHMe2)2]3(THF)2], was used as catalyst for the hydroamination/cyclisation, the hydrosilylation and the sequential hydroamination/hydrosilylation reaction.     

单氢钌配合物催化氢化苯乙烯的位阻效应

研究了溶剂分别为 THF, H2O/THF, CH3CN/THF以及ROH/THF (R＝Me, Et, iso-Pr, tert-Bu)条件下TpRuH(PPh3)- (CH3CN) [Tp＝hydrotris(pyrazolyl)borate]催化氢化苯乙烯生成乙基苯的反应, 发现向干燥THF体系中添加微量 H2O, CH3CN或ROH对催化反应都具有显著的促进作用. 催化机理研究表明, 小分子添加物首先取代TpRuH(PPh3)(CH3CN)中的PPh3配体形成中间体TpRuH(CH3CN)L (L＝H2O, CH3CN或ROH), 降低空间位阻, CH3CN配体随后被苯乙烯取代生成中间体 TpRuH(H2C＝CHPh)L; η2-苯乙烯插入Ru—H键后形成的Ru-烷基中间物与H2反应生成η2-H2配合物 TpRu(CH2CH2Ph)(H2)L或TpRu[CH(CH3)Ph](H2)L, 进而发生σ-复分解反应生成乙基苯完成催化循环.     

A new route to coordination complexes of nitroxyl (HN=O) via insertion reactions of nitrosonium triflate with transition-metal hydrides

Nitrosonium triflate reacts with cold methylene chloride solutions of mer,trans-ReH(CO)3(PPh3)2 (1) with 1,1-insertion of NO+ into the Re-H bond to give the orange nitroxyl complex [mer,trans-Re(NH=O)(CO)3(PPh3)2][SO3CF3] (3) in 86% isolated yield. Use of [NO][PF6] or [NO][BF4] gives analogous insertion products at low temperature, which decompose on warning to ambient temperature to the fluoride complex mer,trans-ReF(CO)3(PPh3)2 (4). A related 1,1-insertion is observed in the reaction of 1 with [PhN2][PF6] in acetone that affords the yellow-orange phenyldiazene salt [mer,trans-Re(NH=NPh)(CO)3(PPh3)2][PF6] (2), which has been characterized by X-ray crystallographic methods. The methyl derivative mer,trans-Re(CH3)(CO)3(PPh3)2 (5) also undergoes a 1,1-insertion reaction with [NO][SO3CF3] to give the nitrosomethane adduct [mer,trans-Re{N(CH3)=O}(CO)3(PPh3)2][SO3CF3] (6) as red crystals in 75% yield. The nitroxyl complex [cis,trans-OsBr(NH=O)(CO)2(PPh3)2][SO3CF3] (8) can be similarly prepared as orange crystals in 52% yield by reaction of cis,trans-OsHBr(CO)2(PPh3)2 (7) with [NO][SO3CF3] in cold methylene chloride solution.     

Bis(phosphinimino)methanide rare earth amides: synthesis, structure, and catalysis of hydroamination/cyclization, hydrosilylation, and sequential hydroamination/hydrosilylation

A series of yttrium and lanthanide amido complexes [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}] (Ln=Y, La, Sm, Ho, Lu) were synthesized by three different pathways. The title compounds can be obtained either from [Ln{N(SiHMe(2))2}3(thf)2] and [CH(2)(PPh(2)NSiMe(3))2] or from KN(SiHMe(2))2 and [Ln{CH(PPh(2)NSiMe(3))2}Cl(2)]2, while in a third approach the lanthanum compound was synthesized in a one-pot reaction starting from K{CH(PPh(2)NSiMe(3))2}, LaCl3, and KN(SiHMe(2))2. All the complexes have been characterized by single-crystal X-ray diffraction. The new complexes, [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}], were used as catalysts for hydroamination/cyclization and hydrosilylation reactions. A clear dependence of the reaction rate on the ionic radius of the center metal was observed, showing the lanthanum compound to be the most active one in both reactions. Furthermore, a combination of both reactions--a sequential hydroamination/hydrosilylation reaction--was also investigated.     

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups

A novel organic-inorganic hybrid 2D molecular space with regular triphenylphosphine groups (triphenylphosphineamidephenylsilica, PPh(3)APhS) was successfully synthesized through grafting triphenylphosphine groups in the 2D structure of layered aminophenylsilica dodecyl sulfate (APhTMS-DS), which was developed in our previous research, with regular ammonium groups. The 2D structures were kept after the grafting reaction of triphenylphosphine groups in PPh(3)APhS. The catalytic potentials of 2D molecular space with regular triphenylphosphine groups were investigated. An unusual catalytic effect was found in a carbon-phosphorus ylide reaction. The PPh(3)-catalyzed reaction of modified allylic compounds, including bromides and chlorides with tropone yielded a [3 + 6] annulation product. However, an unusual [8 + 3] cycloadduct was obtained in the reaction of modified allylic compounds, including bromides and chlorides with tropone catalyzed by PPh(3)APhS. Otherwise, the stable catalytic intermediate was successfully separated, and the reaction activity of the catalytic intermediate was confirmed in the reaction of modified allylic compounds with tropone catalyzed by PPh(3)APhS. This research is the first successful example of directly influencing catalytic reaction processes and product structures by utilizing the chemical and geometrical limits of 2D molecular spaces with regular catalyst molecules and affords a novel method for controlling catalytic reaction processes and catalyst design.     

介孔SBA-15棒负载的Pd3Cl催化剂催化Sonogashira偶联反应（英文）

通过静电吸引策略将具有高度分散性的原子精确纳米团簇[Pd3Cl(PPh2)2(PPh3)3]+(Pd3Cl)负载在介孔SBA-15棒上。结构明确的Pd3Cl/SBA-15催化剂在以水作为溶剂以及温和的反应条件下对催化Sonogashira碳-碳偶联反应展现了较好的催化性能以及循环性。在此基础上,我们研究了Pd3Cl团簇结构与性能之间的关系,并证实内核的Pdδ+(0<δ<2)与配体之间的协同效应是催化反应的关键。     

Room-temperature regioselective C-H/olefin coupling of aromatic ketones using an activated ruthenium catalyst with a carbonyl ligand and structural elucidation of key intermediates

Mechanistic studies of the ruthenium-catalyzed reaction of aromatic ketones with olefins are presented. Treatment of the original catalyst, RuH(2)(CO)(PPh(3))(3), with trimethylvinylsilane at 90 °C for 1-1.5 h afforded an activated ruthenium catalyst, Ru(o-C(6)H(4)PPh(2))(H)(CO)(PPh(3))(2), as a mixture of four geometric isomers. The activated complex showed high catalytic activity for C-H/olefin coupling, and the reaction of 2'-methylacetophenone with trimethylvinylsilane at room temperature for 48 h gave the corresponding ortho-alkylation product in 99% isolated yield. The activated catalyst was thermally robust and showed excellent catalytic activity under refluxing toluene conditions. (1)H and (31)P NMR studies of the C-H/olefin coupling at room temperature suggested that an ortho-ruthenated complex, P,P'-cis-C,H-cis-Ru(2'-(6'-MeC(6)H(4)C(O)Me))(H)(CO)(PPh(3))(2), participated in the reaction as a key intermediate. Isotope labeling studies using acetophenone-d(5) indicated that the rate-limiting step was the C-C bond formation, not the C-H bond cleavage, and that each step prior to the reductive elimination was reversible. The rate of C-H/olefin coupling was found to exhibit pseudo first-order kinetics and to show first-order dependence on the ruthenium complex concentration.     

Mo-Ag类立方烷异四核簇[Mo~2Ag~2S~4](TDT)~2(PPh~3)~2的合成, 结构表征和反应性

采用[2+1+1]的设计合成模式, 以二核化合物[Mo~2S~4(TDT)~2](Me~4N)~2(1,TDT=S~2C~6H~3CH~3^2^-)为起始物,与Ag(PPh~3)~3(NO~3)反应,首次合成[Mo~2Ag~2S~4](TDT)~2(PPh~3)~2·CH~2Cl~2(2)的类立方烷异四核簇合物.文中报道了该化合物的晶体结构,红外光谱,紫外可见光谱和电化学研究结果, 以此簇合物和过量的Cu(PPh~3)~2dtp[dtp=S~2P(OEt)~2]反应发现金属Ag可被Cu取代,形成其同系物[Mo~2Cu~2S~4](TDT)~2(PPh~3)~2.这是迄今研究较少的原子簇反应类型.化合物的结晶学参数如下:单斜晶系,空间群:P2~1/n,晶胞参数:a=1.7202(4)nm,b=1.7632(3)nm,c=1.9033(8)nm.β=99.24(3)°,V=5.698(3)nm^3,Z=4,D~c=1.69g/cm^3.对于6158个衍射,最终结构偏离因子R=0.040,R~W=0.048     

Facile Ru-H2 heterolytic activation and intramolecular proton transfer assisted by basic N-centers in the ligands

The use of the phosphine PPh2py instead of PPh3 in complexes of the type [Cp*RuH(P)2] enormously alters the kinetic control of the proton-transfer reactions over this compound and its chemical behavior. The reaction at low temperature of [Cp*RuH(PPh2py)2], 2, with HBF4 gives as products the classical dihydride trans-[Cp*RuH2(PPh2py)2](BF4), 3 (1 equiv of HBF4) or the dihydrogen-bonded complex [Cp*RuHH(PPh2pyH)(PPh2py)](BF4)2, 4 (2 equiv of HBF4). These complexes exhibit very accessible intramolecular processes of proton transfer, and finally, a slow release of H2 takes place at room temperature. Derivatives 2 and 3 are active catalysts for the deuterium labeling of H2 using methanol-d4 as an isotopic source. This demonstrates that the release of hydrogen is reversible, that the heterolytic activation of H2 is an easy process, and that acid species participate in the intramolecular proton-transfer processes. These observations are supported by reaction-coordinate calculations at the DFT/B3LYP level that show the existence of a low-energy reaction path that easily transforms the classical trans dihydride complex into the nonclassical cis dihydrogen compound in a reversible way, through the involvement of hydrogen- and dihydrogen-bonded intermediates and the essential participation of the pyridine centers. The different energy minima of this reaction profile are very accessible through low-energy transition states, all of which have been located.     

Theoretical investigation on the isomerization reaction of 4-phenyl-hexa-1,5-enyne catalyzed by homogeneous Au catalysts

By carrying out density functional theory calculations, we have performed a detailed mechanism study for the cycloisomerization reaction of 4-phenyl-hexa-1,5-enyne catalyzed by homogeneous gold to better understand the observed different catalytic activity of several catalysts, including (PPh(3))AuBF(4), (PPh(3))AuCl, AuCl(3), and AuCl. In all situations, the reaction is found to involve two major steps: the initial nucleophilic addition of the alkynyl onto the alkene group and the subsequent 1,2-H migration. It is found that the potential energy surface profiles of systems are very different when different catalysts are used. For (PMe(3))AuBF(4)- and (PMe(3))AuCl-mediated systems, the nucleophilic addition is the rate-determining step, and the calculated free energy barriers are 15.2 and 41.9 kcal/mol, respectively. In contrast, for AuCl(3)- and AuCl-mediated systems, the reactions are controlled by the dissociations of catalysts from the product-like intermediates, and the calculated dissociation energies are 18.1 and 21.7 kcal/mol, respectively, which are larger than both the corresponding free energy barriers of the nucleophilic addition and the H-migration processes (8.5 and 7.3 kcal/mol for the AuCl(3)-mediated reaction, and 16.9 and 11.3 kcal/mol for the AuCl-mediated reaction). These results can rationalize the early experimental observations that the reactant conversion rates are 100, 0, and 50% when using (PPh(3))AuBF(4), (PPh(3))AuCl, and AuCl(3) as catalysts, respectively. The present study indicates that both the ligand and counterion of homogeneous Au catalysts importantly influence their catalytic activities, whereas the oxidation state of Au is not a crucial factor controlling the reactivity.