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1.
A series of Ir–PCP pincer precatalysts [(7–6–7‐RPCP)Ir(H)(Cl)] and [(7–6–7‐ArPCP)Ir(H)(Cl)(MeCN)] bearing a novel “7–6–7” fused‐ring skeleton have been synthesized based upon the postulate that the catalytic species would have durability due to their rather rigid structure and high activity owing to the low but sufficient flexibility of their backbones, which are not completely fixed. Treatment of these precatalysts with NaOtBu gave rise to the active 14 electron (14e) species [(7–6–7‐iPrPCP)Ir] and [(7–6–7‐PhPCP)Ir], which can trap hydrogen and were spectroscopically characterized as the tetrahydride complexes. Both [(7–6–7‐iPrPCP)Ir] and [(7–6–7‐PhPCP)Ir] were found to be highly effective in the transfer dehydrogenation of cyclooctane with tert‐butylethylene as the hydrogen acceptor, the initial reaction rate at high temperature (230 °C) being higher for [(7–6–7‐iPrPCP)Ir] than [(7–6–7‐PhPCP)Ir], and the turnover number (TON) of the overall hydrogen transfer being higher for the latter. Nonetheless, the estimated TONs were as high as 4600 and 4820 for the two complexes at this temperature, respectively, which are unprecedented absolute values. In terms of durability, the [(7–6–7‐PhPCP)Ir] complex is the catalyst of choice for this reaction. Structural analysis and computational studies support the importance of the low flexibility of the ligand core.  相似文献   

2.
Two aggregation-induced emission (AIE) macrocycles (DMP[5]-TPE and PCP[5]-TPE) were prepared by embedding Tetraphenylethene (TPE) unit into the skeletons of Dimethoxypillar[5]arene (DMP[5]) and [15]Paracyclophane ([15]PCP) at meso position, respectively. In crystal, the PCP[5]-TPE showed a distorted cavity, and the incubation of hexane inside the DMP[5]-TPE cavity caused a distinct change in the molecular conformation compared to PCP[5]-TPE. There was no complexation between PCP[5]-TPE and 1,4-dicyanobutane (DCB). UV absorption experiments showed the distorted cavity of DMP[5]-TPE hindered association with DCB.  相似文献   

3.
Modified 3,5‐dipyrrolylpyrazole (DPP) derivatives in their protonated form produce planar [2+2]‐type complexes with trifluoroacetate (TFA) ions. These complexes serve as constituent components of ion‐pair‐based assemblies. An essential strategy for the construction of dimension‐controlled organized structures based on these [2+2]‐type complexes is the introduction of aryl rings bearing long alkyl chains, which enables the formation of 2D patterns at interfaces, supramolecular gels, and mesophases.  相似文献   

4.
PCP ligand (1,3-bis-[(diisopropyl-phosphanyl)-methyl]-benzene), and PCN ligand ([3-[(di-tert-butyl-phosphanyl)-methyl]-benzyl]-diethyl-amine) based rhodium dinitrogen complexes (1 and 2, respectively) react with phenyl diazomethane at room temperature to give PCP and PCN-Rh carbene complexes (3 and 5, respectively). At low temperature (-70 degrees C), PCP and PCN phenyl diazomethane complexes (4 and 6, respectively) are formed upon addition of phenyl diazomethane to 1 and 2. In these complexes, the diazo moiety is eta(1) coordinated through the terminal nitrogen atom. Decomposition of complexes 4 and 6 at low temperatures leads only to a relatively small amount of the corresponding carbene complexes, the major products of decomposition being the dinitrogen complexes 1 and 2 and stilbene. This and competition experiments (decomposition of 6 in the presence of 1) suggests that phenyl diazomethane can dissociate under the reaction conditions and attack the metal center through the diazo carbon producing a eta(1)-C bound diazo complex. Computational studies based on a two-layer ONIOM model, using the mPW1K exchange-correlation functional and a variety of basis sets for PCP based systems, provide mechanistic insight. In the case of less bulky PCP ligand bearing H-substituents on the phosphines, a variety of mechanisms are possible, including both dissociative and nondissociative pathways. On the other hand, in the case of i-Pr substituents, the eta(1)-C bound diazo complex appears to be a critical intermediate for carbene complex formation, in good agreement with the experimental results. Our results and the analysis of reported data suggest that the outcome of the reaction between a diazoalkane and a late transition metal complex can be anticipated considering steric requirements relevant to eta(1)-C diazo complex formation.  相似文献   

5.
The self‐inclusion behavior of monoester copillar[5]arenes depends on the position of the ester group, which causes different guest selectivities. Monoester copillar[5]arenes bearing an acetate chain can form stable self‐inclusion complexes in low‐ and high‐concentration solution and exhibit high guest selectivity. However, a monoester copillar[5]arene bearing a butyrate chain can not form a self‐inclusion complex and exhibits low guest selectivity. Thus, a new class of stable self‐inclusion complexes of copillar[5]arenes was explored to improve the selectivity of molecular recognition.  相似文献   

6.
In the solid state, multilayered [3.3]paracyclophanes (PCPs) 2-6 and tetracyanoethylene (TCNE) form charge-transfer (CT) complexes with a 1:1 stoichiometry. All the benzene rings overlapped each other. All the [3.3]PCP units and dione units assume chair conformations and the transannular distances are shorter than those of the corresponding free multilayered [3.3]PCP except for the dione unit in the four-layered dione 6. In the crystal-packing diagrams, the PCP and TCNE are located in alternating donor-acceptor stacking in columns, and effective short contacts are observed in the neighboring molecules.  相似文献   

7.
Summary: By a sidearm approach, a series of titanium complexes bearing an [O, N, S] tridentate ligand have been synthesized and proven to be highly active for ethylene polymerization. The complexes also show excellent ability to copolymerize ethylene with hex‐1‐ene and norbornene. The effects of the different sidearms on the catalytic behavior of the complexes were studied in detail.

The copolymerization of ethylene with hex‐1‐ene using titanium complexes bearing [O, N, S] tridentate ligands as catalysts.  相似文献   


8.
5,20‐Bis(ethoxycarbonyl)‐[28]hexaphyrin was synthesized by acid catalyzed cross‐condensation of meso‐diaryl‐substituted tripyrrane and ethyl 2‐oxoacetate followed by subsequent oxidation. This hexaphyrin was found to be a stable 28π‐antiaromatic compound with a dumbbell‐like conformation. Upon oxidization with PbO2, this [28]hexaphyrin was converted into an aromatic [26]hexaphyrin with a rectangular shape bearing two ester groups at the edge side. The [28]hexaphyrin can incorporate two NiII or CuII metals by using the ester carbonyl groups and three pyrrolic nitrogen atoms to give bis‐NiII and bis‐CuII complexes with essentially the same dumbbell‐like structure. The antiaromatic properties of the [28]hexaphyrin and its metal complexes have been well characterized.  相似文献   

9.
Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh3)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me2NCH2)2C6H3}(PPh3)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh3)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=iPr or tBu, P*CHP*) and the complex [RuCl{2,6‐(Me2NCH2)2C6H3}(PPh3)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh3)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh3)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh3)] complexes and chiral [RuCl(P*CP*)(PPh3)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.  相似文献   

10.
New and improved preparative routes to the previously known PCP ligands cis-1,3-bis(di-isopropylphosphinito)cyclohexane and cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane are reported. They react with 1 equivalent of dichloro(1,5-cyclooctadiene)platinum(II) [(COD)PtCl2] to give the cis coordinated complex cis-[PtCl2{cis-1,3-bis(di-isopropylphosphinito)}cyclohexane] and the C(sp3)-H activated complex trans-[PtCl{cis-1,3-bis(di-tert-butylphosphino)}cyclohexane]. The new PCP ligand cis-1,3-bis(di-tert-butylphosphinito)cyclohexane was synthesised and reacts with [(COD)PtCl2] giving the di-nuclear trans-[PtCl2{cis-1,3-bis(di-tert-butylphosphinito)cyclohexane}]2, which is highly insoluble. All metal complexes were characterised with X-ray crystallography. DFT calculations indicate that the inability of the phosphinite ligands to cyclometallate is due to a kinetic barrier, possibly involving an axial-equatorial conformational change necessary for the C-H activation process.  相似文献   

11.
A series of platinum(II) complexes supported by the tridentate bis(phosphine)phosphido ligand bis(2-diisopropylphosphinophenyl)phosphide) [(i)Pr-PPP] have been synthesized and characterized (1-4). X-Ray structural studies of [(i)Pr-PPP]PtCl (1) and [(i)Pr-PPP]PtCH(3) (3) complexes show meridional [(i)Pr-PPP] ligands around approximately square-planar platinum centers. Structural data and NMR analysis highlight a strong trans influence for the phosphido phosphorous donor, comparable to that of the anionic aryl carbon of the classic PCP pincer complexes. A series of thermally stable [PPP]Pt(IV) compounds, including [PPP]Pt(CH(3))(2)X [X = I (5) and SbF(6) (6)], were also synthesized. The study of the binding affinity of SO(2) and NO to complex 1 has also been addressed.  相似文献   

12.
Nickel and palladium methoxides [(iPrPCP)M‐OMe], which contain the iPrPCP pincer ligand, decompose upon heating to give products of different kinds. The palladium derivative cleanly gives the dimeric Pd0 complex [Pd(μ‐iPrPCHP)]2 (iPrPCHP=2,6‐bis(diisopropylphosphinomethyl)phenyl) and formaldehyde. In contrast, decomposition of [(iPrPCP)Ni‐OMe] affords polynuclear carbonyl phosphine complexes. Both decomposition processes are initiated by β‐hydrogen elimination (BHE), but the resulting [(iPrPCP)M‐H] hydrides undergo divergent reaction sequences that ultimately lead to the irreversible breakdown of the pincer units. Whereas the Pd hydride spontaneously experiences reductive C?H coupling, the decay of its Ni analogue is brought about by its reaction with formaldehyde released in the BHE step. Kinetic measurements showed that the BHE reaction is reversible and less favourable for Ni than for Pd for both kinetic and thermodynamic reasons. DFT calculations confirmed the main conclusions of the kinetic studies and provided further insight into the mechanisms of the decomposition reactions.  相似文献   

13.
The mechanism of (PCP)Ir-catalyzed transfer-dehydrogenation has been elucidated for the prototypical substrate/acceptor couple, COA/TBE, at 55 degrees C (COA = cyclooctane; TBE = tert-butylethylene). The catalytic cycle may be viewed as the sum of two reactions: (i) hydrogenation of TBE by (PCP)IrH2 and C-H addition of a second mole of TBE to give (PCP)IrH(tert-butylvinyl), and (ii) dehydrogenation of COA by (PCP)IrH(tert-butylvinyl) to give (PCP)IrH2, COE, and TBE. These two stoichiometric reactions have been observed independently and their kinetics determined. The overall catalysis has also been monitored in situ, and (PCP)IrH2 and (PCP)IrH(tert-butylvinyl) have been observed as the resting states; the ratio of these two complexes is found to be proportional to [TBE]2. Based upon the proportionality constant thus obtained and the catalytic rate as a function of [TBE] (which reaches a maximum at ca. 0.3 M), the respective rate constants for the hydrogenation and dehydrogenation segments can be obtained. Good agreement is found between the rates independently obtained from stoichiometric and catalytic runs. Within the overall TBE-hydrogenation reaction, labeling experiments indicate that the rate-determining step is the reductive elimination of TBA (2,2-dimethylbutane) from (PCP)IrH(tert-butylethyl) (which is formed via insertion of TBE into an Ir-H bond of (PCP)IrH2). Based upon considerations of microscopic reversibility, it can be further inferred that the rate-determining step for the alkane dehydrogenations is C-H addition (and not beta-H elimination).  相似文献   

14.
Palladium and platinum complexes of fulleienes C60 and C70 containing the axially chiral ligand (—)-BITIANP (BITIANP is 2,2’-bis(diphenylphosphino)-3,3’-bi(benzo[b]thiophene)) and pynolidino[60]fullerene bearing a planar chiral organometallic π-complex substituent in the heteiocyclic ring were studied by circular dichroism (CD) spectroscopy.  相似文献   

15.
Reaction of (PCP)Ru(CO)(Cl) (1) with NaBAr'4 yields the bimetallic product [[(PCP)Ru(CO)](2)(mu-Cl)][BAr'4] (2). The monomeric five-coordinate complexes [(PCP)Ru(CO)(eta1-ClCH2Cl)][BAr'4] (3) and [(PCP)Ru(CO)(eta1-N2)][BAr'4] (4) are synthesized upon reaction of (PCP)Ru(CO)(OTf) (6) with NaBAr'4 in CH2Cl2 or C6H5F, respectively. The solid-state structures of 2, 3, and 4 have been determined by X-ray diffraction studies of single crystals. The reaction of 3 with PhCHN2 or PhCCH affords carbon-carbon coupling products involving the aryl group of the PCP ligand in transformations that likely proceed via the formation of Ru carbene or vinylidene intermediates. Density functional theory and hybrid quantum mechanics/molecular mechanics calculations were performed to investigate the bonding of weak bases to the 14-electron fragment [(PCP)Ru(CO)]+ and the energetics of different isomers of the product carbene and vinylidene complexes.  相似文献   

16.
Eberhard MR 《Organic letters》2004,6(13):2125-2128
[reaction: see text] The Heck reaction of phenyl halides with styrene using a series of related PCP pincer palladium(II) complexes was studied in order to evaluate the effect of ligand structure and electronics on the catalytic activity and to investigate the nature of the catalyst species. We suggest these pincer complexes are precatalysts for highly active forms of metallic palladium. This conclusion is based on kinetic studies (induction periods, sigmoidal kinetics), Hg drop tests, quantitative poisoning experiments, and NMR studies.  相似文献   

17.
Coordination of ten calix[4]arenes bearing boronic acid moieties with five monosaccharides was studied by fluorescence spectrometry. The stability constants (K2) of the complexes and Gibbs free energy change ( ‐ ΔG0) of the coordination reactions were calculated according to the modified Hilderbrand‐Benesi equation. The results obtained indicated that the coordination ability of D‐( ‐ )‐fructose with calix[4] arenes bearing boronic acid moieties was stronger than that of the other monosaccharides. And these calix[4]arene derivatives might be used for identification of L‐( ‐ )‐sorbose.  相似文献   

18.
Two new [C^N]‐type palladacyclic dinuclear complexes bearing carboxylate‐containing N‐heterocyclic carbenes (NHCs) were synthesized, and in both cases the carboxylato‐NHC ligand adopts a bridging mode. Both complexes proved to be suitable precursors, which can be used to divergently access palladacycles bearing ester‐ or COOH‐functionalized NHCs upon esterification or acidolysis. In the esterification reactions, alkyl halides are found to selectively react with the carboxylato moieties, and the palladacycle scaffold is retained even when excess haloalkane is employed. In the acidolysis reactions, the desired COOH‐tethered complexes can only be obtained when stoichiometric acid (with respect to Pd) is used, while excess acid destroys the metallacycle scaffold. Finally, a preliminary catalytic study reveals the good performances of all newly synthesized complexes in direct aromatic C─H functionalization reactions with alkynes. Poisoning experiments indicate that these hydroarylation reactions are likely to be homogeneously catalyzed.  相似文献   

19.
Zhang  Bo  Wang  Haiying  Yan  Xuechao  Duan  Yu-Ai  Guo  Shuai  Luo  Fei-Xian 《Transition Metal Chemistry》2020,45(2):99-110
Transition Metal Chemistry - A series of ruthenium [NNN]- or [NCN]-type complexes (3–7) bearing PPh3 ancillary ligands have been synthesized from pyridine- or phenylene-bridged bis(triazoles)...  相似文献   

20.
[NiFe] hydrogenase, the enzyme of which catalyzes the reversible oxidation of molecular hydrogen to protons and electrons, contains a unique heterodinuclear thiolate-bridged Ni-Fe complex in which the iron center is coordinated by CO and CN. We have synthesized dithiolate-bridged Ni-Fe complexes bearing CO and CN ligands to model the active center of [NiFe] hydrogenase. The Ni-Fe complexes containing a [(CN)2(CO)2Fe(mu-S2)NiS2] framework are the closest yet structural models of [NiFe] hydrogenase.  相似文献   

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