丙烯酸甲酯/乙烯基吡啶共聚物铑配合物的配体空间结构对甲醇羰基化反应催化性能的影响

针对共聚物配体聚合的随机性及其共聚结构单元的复杂性 ,运用XPS及红外光谱等分析手段 ,探讨了共聚物铑配合物微观结构对催化性能的影响 ;研究了丙烯酸甲酯 2 乙烯基吡啶和丙烯酸甲酯 4 乙烯基吡啶两种共聚物与铑的不同配比的配合物的活性 ,考察了相同配比的共聚物配合物结构单元、温度等因素对消化活性的影响 ,为催化剂结构的合理设计提供了理论参考     

Dual effect of halides in the Stille reaction: in situ halide metathesis and catalyst stabilization

Halide anions can increase or decrease the transmetallation rate of the Stille reaction through in situ halide metathesis. Although the influence of the halogen present in oxidative addition complexes on the transmetallation rate with organostannanes was already known, the application of in situ halide metathesis to accelerate cross-coupling reactions with organometallic reagents is not described in the literature yet. In addition a second unprecedented role of halides was discovered. Halide anions stabilize the [Pd(0)(L)(2)] catalyst in Stille reactions, by means of [Pd(0)X(L)(2)](-) formation (X=Cl, I), hereby preventing its leaching from the catalytic cycle. Both arene (iodobenzene) and azaheteroarene (2-halopyridine, halopyrazine, 2-halopyrimidine) substrates were used.     

Synthesis and characterization of asymmetric NHC complexes

New chiral and non-chiral rhodium(I)–NHC complexes were synthesized. The first attempt by deprotonation of an imidazolinium salt with KOtBu and reaction with [Rh(COD)Cl]₂ leads to the corresponding rhodium(I) complex. Due to the basic conditions during the reaction a loss of chirality occurs. An alternative transmetallation reaction with a silver(I)–NHC complex yields the desired rhodium(I)–NHC complex under retention of chirality. Both Rh complexes were fully characterized by analytical methods.     

Carbene complexes of rhodium and iridium from tripodal N-heterocyclic carbene ligands: synthesis and catalytic properties

Two tripodal trisimidazolium ligand precursors have been tested in the synthesis of new N-heterocyclic carbene rhodium and iridium complexes. [Tris(3-methylbenzimidazolium-1-yl)]methane sulfate gave products with coordination of the decomposed precursor. [1,1,1-Tris(3-butylimidazolium-1-yl)methyl]ethane trichloride (TIMEH(3)(Bu)) coordinated to the metal in a chelate and bridged-chelate form, depending on the reaction conditions. The crystal structures of two of the products are described. The compounds resulting from the coordination with TIME(Bu) were tested in the catalytic hydrosilylation of terminal alkynes.     

A mechanistic investigation into the elimination of phosphonium salts from rhodium-TRIPHOS complexes under methanol carbonylation conditions

Phosphine modified rhodium complexes are currently the topic of considerable research as methanol carbonylation catalysts, but often suffer from poor stability. This paper reports on an investigation into how coordination mode affects the elimination of phosphonium salts from rhodium complexes, namely [trans-RhCl(CO)(PPh(3))(2)] , [RhCl(CO)(dppe)] , [RhCl(CO)(dppb)](2), [Rh(TRIPHOS)(CO)(2)]Cl . These complexes are all potential pre-catalysts for methanol carbonylation. The reaction of these complexes with methyl iodide at 140 degrees C under both N(2) and CO atmospheres has been studied and has revealed clear differences in the stability of the corresponding Rh(iii) complexes. In contrast to both monomeric and dimeric that react cleanly with CH(3)I to give stable Rh(iii) acetyl complexes, forms a novel bidentate complex after the elimination of the one arm of the ligand as a quaternised phosphonium salt. The structure of this complex has been determined spectroscopically and using X-ray crystallography. The mechanism of formation of this novel complex has been investigated using (13)CH(3)I and strong evidence that supports a dissociative mechanism as the means of phosphine loss from the rhodium centre is provided.     

甲醇羰基化的高分子催化剂（PVMRh）的稳定性研究

研究了以交联共聚物（ＰＶＭ）大孔隙树脂为配体的羰基铑配合物的热稳定性和抗空气氧化稳定性．这种类型的高分子铑催化剂不仅比类似的小分子铑配合物在甲醇羰基化反应中有着明显的高活性，而且在稳定性方面亦有着小分子配合物不可比拟的特点。实验结果表明，这类高分子催化剂在空气中的稳定温度达到１７０℃。在空气中室温放置５万小时后，其催化剂仍能保持不变。     

Thione complexes of Rh(I): a first comparison with the bonding and catalytic activity of related carbene and imine compounds

Heterocyclic mono(thione), trans-bis(thione), cis-bis(thione), trans-(carbene-thione), cis-(carbene-thione), trans-(phosphine-thione) and mono(imine) complexes of rhodium(I) have been prepared and fully characterised. Chloro(eta(4)-1,5-cyclooctadiene)(L)rhodium(I)(1a, L = 1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione; 1b L = 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-2-thione) appear as isomers at room temperature due to slow coordination exchange on the S-donor atom. In the three structures determined, the substituent on the sulfur appears syn to Cl. Hindered rotation about the Rh-carbene bond is revealed in the NMR spectra of seven new complexes with isopropyl substituents on the heterocyclic carbene ligands. The trans influence of the thione ligands is smaller than that of carbenes but larger than that shown by imines and chloride. Thione complexes are better catalyst precursors than the carbene complexes for the hydroformylation of 1-hexene under the chosen reaction conditions: 80 degrees C, 8 MPa CO-H2(1:1), 16 h, 1:1000 catalyst to 1-hexene ratio.     

Potassium ion-mediated non-covalent bonded coordination polymers

Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl(4)(DMSO-κS)(2)K](n), 1, and [cis-RhCl(4)(DMSO-κS)(2)K·3H(2)O](n), 2, and one metastable compound [trans-RhCl(4)(DMSO-κS)(2)K·0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl(4)(DMSO-κS)(2)](-) complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl(-) and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K(+) and Cl(-) exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl(4)(DMSO-κS)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-κS > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K(+)-ligand interactions whereas direct experimental evidences of K(+)-Cl(-) interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.     

Cationic and neutral diphenyldiazomethanerhodium(I) complexes as catalytically active species in the C-C coupling reaction of olefins and diphenyldiazomethane

Cationic rhodium(I) complexes cis-[Rh(acetone)2(L)(L')]+ (2: L = L'=C8H14; 3: L=C8H14; L'=PiPr3; 4: L=L'=PiPr3), prepared from [RhCl(C8H14)2]2] and isolated as PF6 salts, catalyze the C-C coupling reaction of diphenyldiazomethane with ethene, propene, and styrene. In most cases, a mixture of isomeric olefins and cyclopropanes were obtained which are formally built up by one equivalent of RCH=CH2 (R = H, Me, Ph) and one equivalent of CPh2. The efficiency and selectivity of the catalyst depends significantly on the coordination sphere around the rhodium(I) center. Treatment of 4 with Ph2CN2 in the molar ratio of 1:1 and 1:2 gave the complexes trans-[Rh(PiPr3)2(acetone)(eta1-N2CPh2)]PF6 (8) and trans-[Rh(PiPr3)2(eta1-N2CPh2)2]PF6 (9), of which 8 was characterized by X-ray crystallography. Since 8 and 9 not only react with ethene but also catalyze the reaction of C2H4 and free Ph2CN2, they can be regarded as intermediates (possibly resting states) in the C-C coupling process. The lability of 8 and 9 is illustrated by the reactions with pyridine and NaX (X=Cl, Br, I, N3) which afford the mono(diphenyldiazomethane)rhodium(I) compounds trans-[Rh(PiPr3)2(py)(eta1-N2CPh2)]PF6 (10) and trans-[RhX(eta1-N2CPh2)(PiPr3)2] (11-14), respectively. The catalytic activity of the neutral complexes 11 - 14 is somewhat less than that of the cationic species 8, 9 and decreases in the order Cl > Br> I > N3.     

Interplay between solvent and counteranion stabilization of highly unsaturated rhodium(III) complexes: facile unsaturation-induced dearomatization

Abstraction of the chloride ligand from the PCN-based chloromethylrhodium complex 2 by AgX (X=BF(4)(-), CF(3)SO(3)(-)) or a direct C-C cleavage reaction of the PCN ligand 1 with [(coe)(2)Rh(solv)(n)](+)X(-) (coe=cyclooctene) lead to the formation of the coordinatively unsaturated rhodium(III) complexes 3. Compound 3 a (X=BF(4)(-)) exhibits a unique medium effect; the metal center is stabilized by reversible coordination of the bulky counteranion or solvent as a function of temperature. Reaction of [(PCN)Rh(CH(3))(Cl)] with AgBAr(f) in diethyl ether leads to an apparent rhodium(III) 14-electron complex 4, which is stabilized by reversible, weak coordination of a solvent molecule. This complex coordinates donors as weak as diethyl ether and dichloromethane. Upon substitution of the BF(4)(-) ion in [(PCN)Rh(CH(3))]BF(4) by the noncoordinating BAr(f)(-) ion in a noncoordinating medium, the resulting highly unsaturated intermediate undergoes a 1,2-metal-to-carbon methyl shift, followed by beta-hydrogen elimination, leading to the Rh-stabilized methylene arenium complex 5. This process represents a unique mild, dearomatization of the aromatic system induced by unsaturation.     

顺二羰基(三齿N-配体)铑(Ⅰ)配合物的分子内取代反应

报道了3种不同结构的三齿N-配体以及与铑形成的顺二羰基配合物.研究表明,正方平面顺二羰基铑配合物在遇热条件下,其配体中未参与配位的授体N原子可取代它的一个端羰基而形成新的三齿配位结构.而在CO气氛下,三齿配位结构回到二齿配位状态.正方平面铑配合物的这一特殊分子内取代可逆反应过程,对于研究这类配合物结构、性能及催化作用均有重要的意义.非正方平面顺二羰基铑配合物则不发生上述分子内取代反应.利用IR和XPS对上述反应进行了表征.     

m-Carborane-based chiral NBN pincer-metal complexes: synthesis, structure, and application in asymmetric catalysis

We have succeeded in synthesizing m-carborane-based chiral NBN-pincer ligands, 1,7-bis(oxazolinyl)-1,7-dicarba-closo-dodecaborane (Carbox) (7-9). The combination of bis(hydroxyamides) and 3 equiv of diethylaminosulfur trifluoride (DAST) is a key step for cyclization to form oxazoline rings in excellent yields. X-ray crystal structures of these ligands confirmed three donor sites, one central B and two flanking N atoms in fixed positions. The electrophilic halogenation of the Carbox pincer ligands with iodine and a catalytic amount of Lewis acid led to ring-opening of the oxazolines and afforded bis(haloamides) (13 and 14). The air- and moisture-stable Carbox pincer complexes of rhodium(III), nickel(II), and palladium(II) were synthesized by the oxidative addition of RhCl(3)·3H(2)O, Ni(COD)(2), and Pd(CH(3)CN)(4)[BF(4)](2) to the Carbox pincer ligands (7-9), respectively. The catalytic activity of the rhodium(III) complexes (18-20) was examined for the asymmetric conjugate reduction of α,β-unsaturated esters and reductive aldol reaction. Among these catalysts, [(S,S)-Carbox-iPr]Rh(OAc)(2)·H(2)O (18) showed the highest enantioselective catalytic ability for both asymmetric conjugate reduction and reductive aldol reaction.     

顺二羰基铑（Ⅰ）共聚物催化剂的合成,结构与催化甲醇羰基化反应性能的研究

我们曾报道一系列含有两种不同配位基团的高分子共聚物与四羰基二氯二铑形成的顺二羰基铑(Ⅰ)配合物。这些配合物在催化甲醇羰基化反应中显示出高催化活性和高稳定性。本文采用4-乙烯吡啶(Y)和丙烯酸甲酯(B)共聚物为配体,对其与四羰基二氯二铑形成的配合物(YBRh)进行了表征。对该系列配合物催化甲醇羰基化生成乙酸的性能进行了评价。     

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.     

Intramolecular reaction of polymer coordinated cationic rhodium complex

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Highly efficient iridium catalyst for asymmetric transfer hydrogenation of aromatic ketones under base-free conditions

[reaction: see text] Catalytic systems generated in situ from the chiral PNNP ligands with iridium or rhodium hydride complexes exhibited excellent catalytic activity and good enantioselectivity in the asymmetric transfer hydrogenation of aromatic ketones without added base. The best result was obtained in the IrH(CO)(PPh(3))(3)-ligand 2 catalytic system with up to 99% yield and 97% ee.     

Dinuclear rhodium and iridium complexes with mixed amido/methoxo and amido/hydroxo bridges

The reactions of [[M(mu-OMe)(cod)](2)] (M = Rh, Ir; cod = 1,5- cyclooctadiene) with p-tolylamine, alpha-naphthylamine, and p-nitroaniline gave complexes with mixed-bridging ligands, [[M(cod)](2)(mu-NHAr)(mu-OMe)]. Similarly, the related complexes [[Rh(cod)](2)(mu-NHAr)(mu-OH)] were prepared from the reactions of [[Rh(mu-OH)(cod)](2)] with p-tolylamine, alpha-naphthylamine, and p-nitroaniline. The reactions of [[Rh(mu-OR)(cod)](2)] (R = H, Me) with o-nitroaniline gave the mononuclear complex [Rh(o-NO(2)C(6)H(4)NH)(cod)]. The syntheses of the amido complexes involve a proton exchange reaction from the amines to the methoxo or hydroxo ligands and the coordination of the amide ligand. These reactions were found to be reversible for the dinuclear complexes. The structure of [[Rh(cod)](2)(mu-NH[p-NO(2)C(6)H(4)])(mu-OMe)] shows two edge-shared square-planar rhodium centers folded at the edge with an anti configuration of the bridging ligands. The complex [[Rh(cod)](2)(mu-NH[alpha-naphthyl])(mu-OH)] cocrystallizes with [[Rh(mu-OH)(cod)](2)] and THF, forming a supramolecular aggregate supported by five hydrogen bridges in the solid state. In the mononuclear [Rh(o-NO(2)C(6)H(4)NH)(cod)] complex the o-nitroamido ligand chelates the rhodium center through the amido nitrogen and an oxygen of the nitro group.     

Cyclic (Amino)(aryl)carbenes (CAArCs) as Strong σ‐Donating and π‐Accepting Ligands for Transition Metals

Cyclic (amino)(aryl)carbenes (CAArCs) result from the replacement of the alkyl substituent of cyclic (alkyl)(amino) carbenes (CAACs) by an aryl group. This structural modification leads to enhanced electrophilicity of the carbene center with retention of the high nucleophilicity of CAACs, and therefore CAArCs feature a small singlet–triplet gap. The isoindolium precursors are readily prepared in good yields, and deprotonation at low temperature, in the presence of [RhCl(cod)]₂ and [(Me₂S)AuCl] lead to air‐stable rhodium and gold CAArC‐supported complexes, respectively. The rhodium complexes promote the [3+2] cycloaddition of diphenylcyclopropenone with ethyl phenylpropiolate, and induce the addition of 2‐vinylpyridine to alkenes by CH activation. The gold complexes allow for the catalytic three‐component preparation of 1,2‐dihydroquinolines from aniline and phenyl acetylene. These preliminary results illustrate the potential of CAArC ligands in transition‐metal catalysis.     

A mechanistic investigation of oxidative addition of methyl iodide to [Tp*Rh(CO)(L)

Reaction of methyl iodide with square planar [kappa(2)-Tp*Rh(CO)(PMe(3))] 1a (Tp* = HB(3,5-Me(2)pz)(3)) at room temperature affords [kappa(3)-Tp*Rh(CO)(PMe(3))(Me)]I 2a, which was fully characterized by spectroscopy and X-ray crystallography. The pseudooctahedral geometry of cationic 2a, which contains a kappa(3)-coordinated Tp* ligand, indicates a reaction mechanism in which nucleophilic attack by Rh on MeI is accompanied by coordination of the pendant pyrazolyl group. In solution 2a transforms slowly into a neutral (acetyl)(iodo) rhodium complex [kappa(3)-Tp*Rh(PMe(3))(COMe)I] 3a, for which an X-ray crystal structure is also reported. Kinetic studies on the reactions of [kappa(2)-Tp*Rh(CO)(L)] (L = PMe(3), PMe(2)Ph, PMePh(2), PPh(3), CO)] with MeI show second-order behavior with large negative activation entropies, consistent with an S(N)2 mechanism. The second-order rate constants correlate well with phosphine basicity. For L = CO, reaction with MeI gives an acetyl complex, [kappa(3)-Tp*Rh(CO)(COMe)I]. The bis(pyrazolyl)borate complexes [kappa(2)-Bp*Rh(CO)(L)] (L = PPh(3), CO) are much less reactive toward MeI than the Tp* analogues, indicating the importance of the third pyrazolyl group and the accessibility of a kappa(3) coordination mode. The results strengthen the evidence in favor of an S(N)2 mechanism for oxidative addition of MeI to square planar d(8) transition metal complexes.     

Coordination features of bis(N-heterocyclic carbenes) and bis(oxazolines) with 1,3-alkylidene-2,4,6-trimethylbenzene spacers. Synthesis of the ligands and silver and palladium complexes

The synthesis of simple imidazolium-based ligand precursors containing a 1,3-alkylidene-2,4,6-trimethylbenzene spacer was examined and different synthetic protocols were applied depending on the nature of the alkylidene arm. For a methylene arm, simple dications 5a,b.2CI were obtained directly. The higher homologue counterparts were conveniently prepared by general multistep routes following a five-step sequence for ethylene dications 6a,b.2Br or a six-step sequence for propylene dications 7a,b.2Br in > or = 52% overall yield. Imidazolium salts based on the shorter methylene spacer were used to prepare palladium complexes (17-20) with N-heterocyclic carbenes via transmetallation from well-defined silver compounds or directly in basic conditions. In order to facilitate spectroscopic characterisation of the palladium species two [Pd(allyl)(bis-oxazoline)]+ (25-26) complexes with the same ligand bridge were synthesized. [PdX2bisL] complexes appeared in solution as mixtures of species, mononuclear with cis- or trans-geometry or oligomeric compounds. The reaction of [PdCl(allyl)]2 and micro-bis(carbene)(AgX)2 complexes in 1 : 1 or in 0.5 : 1 ratio leads to binuclear compounds [Pd2Cl2(allyl)2(micro-bis-carbene)] (19a,19b) and to very labile monomeric [Pd(allyl)(bis-carbene)]+ (20a,20b) compounds, respectively. The preparation of analogous [Pd(allyl)(bis-oxazoline)]+ complexes showed the formation of one of the four possible isomers. [Pd(allyl)(bis-oxazoline)]PF6 complexes were inactive as catalytic precursors in the allylic substitution reaction.