Eight new N‐Hoveyda‐type complexes were synthesized in yields of 67–92 % through reaction of [RuCl2(NHC)(Ind)(py)] (NHC=1,3‐bis(2,4,6‐trimethylphenylimidazolin)‐2‐ylidene (SIMes) or 1,3‐bis(2,6‐diisopropylphenylimidazolin)‐2‐ylidene (SIPr), Ind=3‐phenylindenylid‐1‐ene, py=pyridine) with various 1‐ or 1,2‐substituted ferrocene compounds with vinyl and amine or imine substituents. The redox potentials of the respective complexes were determined; in all complexes an iron‐centered oxidation reaction occurs at potentials close to E=+0.5 V. The crystal structures of the reduced and of the respective oxidized Hoveyda‐type complexes were determined and show that the oxidation of the ferrocene unit has little effect on the ruthenium environment. Two of the eight new complexes were found to be switchable catalysts, in that the reduced form is inactive in the ring‐opening metathesis polymerization of cis‐cyclooctene (COE), whereas the oxidized complexes produce polyCOE. The other complexes are not switchable catalysts and are either inactive or active in both reduced and oxidized states. 相似文献
Reactions of the Grubbs 3rd generation complexes [RuCl2(NHC)(Ind)(Py)] (N‐heterocyclic carbene (NHC)=1,3‐bis(2,4,6‐trimethylphenylimidazolin)‐2‐ylidene (SIMes), 1,3‐bis(2,6‐diisopropylphenylimidazolin)‐2‐ylidene (SIPr), or 1,3‐bis(2,6‐diisopropylphenylimidazol)‐2‐ylidene (IPr); Ind=3‐phenylindenylid‐1‐ene, Py=pyridine) with 2‐ethenyl‐N‐alkylaniline (alkyl=Me, Et) result in the formation of the new N‐Grubbs–Hoveyda‐type complexes 5 (NHC=SIMes, alkyl=Me), 6 (SIMes, Et), 7 (IPr, Me), 8 (SIPr, Me), and 9 (SIPr, Et) with N‐chelating benzylidene ligands in yields of 50–75 %. Compared to their respective, conventional, O‐Grubbs–Hoveyda complexes, the new complexes are characterized by fast catalyst activation, which translates into fast and efficient ring‐closing metathesis (RCM) reactivity. Catalyst loadings of 15–150 ppm (0.0015–0.015 mol %) are sufficient for the conversion of a wide range of diolefinic substrates into the respective RCM products after 15 min at 50 °C in toluene; compounds 8 and 9 are the most catalytically active complexes. The use of complex 8 in RCM reactions enables the formation of N‐protected 2,5‐dihydropyrroles with turnover numbers (TONs) of up to 58 000 and turnover frequencies (TOFs) of up to 232 000 h?1; the use of the N‐protected 1,2,3,6‐tetrahydropyridines proceeds with TONs of up to 37 000 and TOFs of up to 147 000 h?1; and the use of the N‐protected 2,3,6,7‐tetrahydroazepines proceeds with TONs of up to 19 000 and TOFs of up to 76 000 h?1, with yields for these reactions ranging from 83–92 %. 相似文献
Summary: Imidazol(in)ium-2-carboxylates were used as N-heterocyclic carbene (NHC) ligand precursors to convert the [RuCl2(p-cymene)]2 dimer into three ruthenium-arene complexes of the [RuCl2(p-cymene)(NHC)] type. The decarboxylation of NHC · CO2 betaines also provided a convenient synthetic path to prepare five well-known ruthenium-NHC catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda–Grubbs catalysts, via ligand exchange with phosphine-containing, first generation ruthenium-benzylidene or indenylidene complexes. Both procedures are particularly attractive from a practical point of view, because NHC · CO2 adducts are stable zwitterionic compounds that can be stored and handled with no particular precautions. 相似文献
Imidazolium salts (NHCewg ? HCl) with electronically variable substituents in the 4,5‐position (H,H or Cl,Cl or H,NO2 or CN,CN) and sterically variable substituents in the 1,3‐position (Me,Me or Et,Et or iPr,iPr or Me,iPr) were synthesized and converted into the respective [AgI(NHC)ewg] complexes. The reactions of [(NHC)RuCl2(CHPh)(py)2] with the [AgI(NHCewg)] complexes provide the respective [(NHC)(NHCewg)RuCl2(CHPh)] complexes in excellent yields. The catalytic activity of such complexes in ring‐closing metathesis (RCM) reactions leading to tetrasubstituted olefins was studied. To obtain quantitative substrate conversion, catalyst loadings of 0.2–0.5 mol % at 80 °C in toluene are sufficient. The complex with the best catalytic activity in such RCM reactions and the fastest initiation rate has an NHCewg group with 1,3‐Me,iPr and 4,5‐Cl,Cl substituents and can be synthesized in 95 % isolated yield from the ruthenium precursor. To learn which one of the two NHC ligands acts as the leaving group in olefin metathesis reactions two complexes, [(FL‐NHC)(NHCewg)RuCl2(CHPh)] and [(FL‐NHCewg)(NHC)RuCl2(CHPh)], with a dansyl fluorophore (FL)‐tagged electron‐rich NHC ligand (FL‐NHC) and an electron‐deficient NHC ligand (FL‐NHCewg) were prepared. The fluorescence of the dansyl fluorophore is quenched as long as it is in close vicinity to ruthenium, but increases strongly upon dissociation of the respective fluorophore‐tagged ligand. In this manner, it was shown for ring‐opening metathesis ploymerization (ROMP) reactions at room temperature that the NHCewg ligand normally acts as the leaving group, whereas the other NHC ligand remains ligated to ruthenium. 相似文献
[(NHC)(cymene)RuCl2] (NHC=N-heterocyclic carbene) complexes instigate a light-driven gem-hydrogenation of internal alkynes with concomitant formation of discrete Grubbs-type ruthenium carbene species. This unorthodox reactivity mode is harnessed in the form of a “hydrogenative metathesis” reaction, which converts an enyne substrate into a cyclic alkene. The intervention of ruthenium carbenes formed in the actual gem-hydrogenation step was proven by the isolation and crystallographic characterization of a rather unusual representative of this series carrying an unconfined alkyl group on a disubstituted carbene center. 相似文献
Catalytic properties of the silicon-containing carbene complexes of tungsten Me3Si-CH=W(NAr)(OR′)2(1) and PhMe2Si-CH=W(NAr)(OR′)2 (2) and their hydrocarbon analogs Me3C-CH=W(NAr)(OR′)2 (3) and PhMe2C-CH=W(NAr)(OR′)2 (4) (Ar = 2,6-Pri2C6H3, R′ = CMe2CF3) were studied in homometathesis of hex-1-ene, metathesis polycondensation of deca-1,9-diene, and ring opening metathesis
polymerization of cyclooctene. The nature of the carbene fragment in the tungsten catalysts substantially affects their catalytic
activity. Silicon-containing catalysts 1 and 2 were found to be 3−5 times less active than their hydrocarbon analogs 3 and 4. Metathesis polymerization of cyclooctene in the bulk with initiators 1–4 completed within a few minutes to form a block. Stereoregularity of the formed polyoctenamers depends to a considerable extent
on the nature of the carbene fragments in the starting initiators. Initiators 1–2 lead to polyoctenamers mainly containing the cis-units, whereas the use of complexes 3 and 4 affords polyoctenamers mainly containing the trans-units. The structures of novel compound 2 and known complexes 1, 3, and 4 were determined by X-ray diffraction analysis.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1840–1845, September, 2008. 相似文献
The molybdenum silicon-containing carbene complexes PhMe2Si—CH=Mo(NAr)(OR)2 (1), Ph2Si[CH=Mo(NAr)(OR)2]2 (2), and (RO)2(ArN)Mo=CH—(SiMe2)2—CH=Mo(NAr)(OR)2 (Ar = 2,6-Pri2C6H3; R = CMe2CF3) were synthesized by the reaction of the R′— CH=Mo(NAr)(OR)2 compounds (R′ = But or PhMe2C) with silicon-containing vinyl reagents. The structures of complexes 1 and 2 and the known PhMe2C—CH=Mo(NAr)(OCMe2CF3)2 compound were established by X-ray diffraction. The catalytic properties of the silicon-containing carbene complexes in homometathesis
of hex-1-ene and metathesis polymerization of cyclooctene were studied. The catalytic activity of these complexes and the
stereoregularity of the resulting polyoctenamers substantially depend on the nature of the substituent at the carbene carbon
atom.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 247–252, February, 2007. 相似文献
A series of cationic and neutral RuII complexes of the general formula [Ru(L)(X) (tBuCN)4]+X? and [Ru(L)(X)2(tBuCN)3)], that is, [Ru(CF3SO3){NCC(CH3)3}4(IMesH2)]+[CF3SO3]? ( 1 ), [Ru(CF3SO3){NCC(CH3)3}4(IMes)]+[CF3SO3]? ( 2 ), [RuCl{NCC(CH3)3}4(IMes)]+Cl? ( 3 ), [RuCl{NCC(CH3)3}4(IMesH2)+Cl?]/[RuCl2{NCC(CH3)3}3(IMesH2)] ( 4 ), and [Ru(NCO)2{NCC(CH3)3}3(IMesH2)] ( 5 ) (IMes=1,3‐dimesitylimidazol‐2‐ylidene, IMesH2=1,3‐dimesityl‐imidazolin‐2‐ylidene) have been synthesized and used as UV‐triggered precatalysts for the ring‐opening metathesis polymerization (ROMP) of different norborn‐2‐ene‐ and cis‐cyclooctene‐based monomers. The absorption maxima of complexes 1 – 5 were in the range of 245–255 nm and thus perfectly fit the emission band of the 254 nm UV source that was used for activation. Only the cationic RuII‐complexes based on ligands capable of forming μ2‐complexes such as 1 and 2 were found to be truly photolatent in ROMP. In contrast, complexes 3 – 5 could be activated by UV light; however, they also showed a low but significant ROMP activity in the absence of UV light. As evidenced by 1H and 13C NMR spectroscopy, the structure of the polymers obtained with either 1 or 2 are similar to those found in the corresponding polymers prepared by the action of [Ru(CF3SO3)2(IMesH2)(CH‐2‐(2‐PrO)‐C6H4)], which strongly suggest the formation of Ru‐based Grubbs‐type initiators in the course of the UV‐based activation process. Precatalysts that have the IMesH2 ligand showed significantly enhanced reactivity as compared with those based on the IMes ligand, which is in accordance with reports on the superior reactivity of IMesH2‐based Grubbs‐type catalysts compared with IMes‐based systems. 相似文献
Trifluoromethylation of [AuF3(SIMes)] with the Ruppert–Prakash reagent TMSCF3 in the presence of CsF yields the product series [Au(CF3)xF3−x(SIMes)] (x=1–3). The degree of trifluoromethylation is solvent dependent and the ratio of the species can be controlled by varying the stoichiometry of the reaction, as evidenced from the 19F NMR spectra of the corresponding reaction mixtures. The molecular structures in the solid state of trans-[Au(CF3)F2(SIMes)] and [Au(CF3)3(SIMes)] are presented, together with a selective route for the synthesis of the latter complex. Correlation of the calculated SIMes affinity with the carbene carbon chemical shift in the 13C NMR spectrum reveals that trans-[Au(CF3)F2(SIMes)] and [Au(CF3)3(SIMes)] nicely follow the trend in Lewis acidities of related organo gold(III) complexes. Furthermore, a new correlation between the Au−Ccarbene bond length of the molecular structure in the solid state and the chemical shift of the carbene carbon in the 13C NMR spectrum is presented. 相似文献
The utility of [(NHC)(PPh3)RuCl2(CHPh)] for the facile and efficient synthesis of ten complexes of the type [(NHC)(NHCewg)RuCl2(CHR)] with saturated and unsaturated NHC ligands in 85-94% isolated yield via a simple one step synthesis utilizing [AgI(NHCewg)] as NHCewg transfer reagents was demonstrated. 相似文献
Density functional theory calculations have been used to explore the potential of Ru‐based complexes with 1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene (SIMes) ligand backbone ( A ) being modified in silico by the insertion of a C60 molecule ( B and C ), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A , B , and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron‐withdrawing N‐heterocyclic carbene improves the performance of unannulated complex A . The efficiency of complex B is only surpassed by complex A when the backbone of the N‐heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic‐donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A . Overall, this study indicates that such Ru‐based complexes B and C might have the potential to be effective olefin metathesis catalysts. 相似文献
A range of new imidazolium and imidazolinium chlorides bearing biphenyl units on their nitrogen atoms was synthesized. They differed by the electron-withdrawing or -donating nature and the steric bulk of the substituents on their aromatic rings. These various N-heterocyclic carbene (NHC) precursors were combined with the [RuCl2(p-cymene)]2 dimer and potassium tert-butoxide to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)] in situ. The catalytic activity of these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of cyclooctene. The results obtained confirmed the necessity of blocking the ortho-positions of the phenyl rings in the vicinity of the metal center in order to attain high catalytic efficiencies. They also showed that changing the steric and electronic properties of the substituents on the remote phenyl rings of the biphenyl units had no significant influence on the outcome of the polymerization. 相似文献
The compound [RuCl2(CO)(DMA)(PPh3)2] [DMA = dimethylacetamide] was obtained from [RuCl3(PPh3)2-(DMA)] · DMA and CO in DMA. Orange crystals of [RuCl2(CO)(DMA)(PPh3)2] · 1/2CH2Cl2 were isolated by slow evaporation of a CH2Cl2/DMA solution and its structure was determined by single crystal X-ray diffraction. The analogous compounds containing DMF and DMSO were obtained from the precursor ttt-[RuCl2(CO)2(PPh3)2]. Characterization of the other complexes is based on i.r. and n.m.r. spectroscopy, including 31P{1H} data. 相似文献
A series of unsaturated acyclonucleoside bis(POC) prodrugs of E configuration were synthesized through an expeditious, highly efficient and stereoselective one-step procedure from corresponding bis(POC)allylphosphonate through Ru catalyzed cross-coupling metathesis reaction. The [RuCl2(PCy3)(SIPr)(Indenylidene)] and [RuCl2(PCy3)(IMes)(benzylidene)] catalysts were employed; the unsaturated ANP were used bore C5-halovinyl uracil, C5-dihalovinyluracil or furanopyrimidine motifs. The chemical cleavage of biolabile (POC) group is a useful pathway to acid phosphonate derivatives. 相似文献
Summary: Homopolymers and diblock copolymers that contain maltose or glucose residues have been prepared by ring‐opening metathesis polymerization of norbornene derivatives using a molybdenum–alkylidene initiator, Mo(CHCMe2Ph)(N‐2,6‐iPr2C6H3)(OtBu)2 ( A ). These polymerizations took place not only in a living fashion ( = < 1.2) but also with almost quantitative initiation. Two types of ruthenium initiators, (Cy3P)2RuCl2(CHPh) ( B ) and (IMesH2)(Cy3P)RuCl2(CHPh) ( C ), have also been used to compare initiator performance under the same conditions.