The ring size of cyclic amines as relevant feature in the activity of Ru-based complexes for ROMP (original) (raw)
Electronicvs. Steric Hindrance Effects in Amine Ligands to Ru-Based Initiators for ROMP
Journal of the Brazilian Chemical Society, 2014
Complexos do tipo [RuCl 2 (PPh 3 ) 2 (amina) x ], com NH 2 Ph (1; x = 2), NH 2 Bz (2; x = 2) and NHBuPh (3; x = 1) na presença de etildiazoacetato (EDA), foram aplicados em reações de polimerização via metátese por abertura de anel (ROMP) de norborneno (NBE), norbornadieno (NBD) e diciclopentadieno (DCPD). Rendimentos quantitativos de poliNBE foram obtidos a 50 °C por 30 min usando 1 e por 5 min usando 2. Isso ocorreu a 25 °C por 5 min quando foi usado 3. Os valores do índice de polidispersidade (PDI) variaram de 3,5 a 1,6 (M w = 10 4 -10 5 g mol -1 ). O complexo 3 foi ativo para ROMP de NBD e DCPD, bem como para copolimerização de NBE com NBD ou com DCPD. O maior caráter σ-doador de NH 2 Bz em 2, em relação a NH 2 Ph em 1, favoreceu a reatividade do complexo 2 que é hexacoordenado como 1. O ângulo de cone de NHBuPh definiu a pentacoordenação em 3 e a sua melhor reatividade para ROMP, apesar do baixo caráter σ-doador como o de NH 2 Ph. [RuCl 2 (PPh 3 ) 2 (amine) x ]-type complexes, with NH 2 Ph (1; x = 2), NH 2 Bz (2; x = 2) and NHBuPh (3; x = 1) in the presence of ethyldiazoacetate (EDA), were investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE), norbornadiene (NBD) and dicyclopentadiene (DCPD). Quantitative yields of polyNBE were obtained at 50 °C for 30 min with 1 and for 5 min with 2, whereas this occurred at 25 °C for 5 min with 3. Polydispersity index (PDI) values ranged from 3.5 to 1.6 (M w = 10 4 -10 5 g mol -1 ). Complex 3 was active for ROMP of NBD and DCPD, as well as for copolymerizations of NBE with either NBD or DCPD. The high σ-donor character of NH 2 Bz favored the reactivity of the six-coordinated complex 2, contrary to complex 1. The large cone angle of NHBuPh defined the fivecoordination in 3 and the best reactivity for ROMP, in spite of the low σ-donor character as in NH 2 Ph.
Journal of Applied Polymer Science, 2012
Copolymers from norbornene (NBE) with norbornadiene (NBD) were synthesized via ring opening metathesis copolymerization varying the mole fractions of the comonomers (0.8 : 0.2; 0.6 : 0.4; 0.4 : 0.6; 0.2 : 0.8) for a total monomer quantity of 5000 equivalents/[Ru]. The batch reactions were performed with [RuCl 2 (PPh 3 ) 2 (amine)] complex types as precatalysts, where amine is perhydroazepine (1) or piperidine (2), in CHCl 3 (2 mL) in the presence of ethyl diazoacetate (5 lL) for different intervals of times (5, 30, 60, and 120 min) at 40 C. The copolymers were characterized by 13 C NMR. Quantitative yields of isolated materials were obtained from solutions with NBD : NBE 0.8 : 0.2 mole fraction in the presence of 1, decreasing to 70% for NBD : NBE 0.2 : 0.8 solutions. Concerning 2, the yields were 70% at most. Polymeric materials obtained with 1 were less soluble in CHCl 3 than those synthesized with 2. The dependence of the reaction yields and occurrence of crosslinking on the starting NBE : NBD proportion related to reactivity of the complexes 1 and 2 were discussed. A few differences in the amines such as ancillary ligands were sufficient to change the reactivity of the {RuCl 2 (PPh 3 )} moiety complex to provide copolymers with different compositions.
Preparation of ruthenium(II) chloride complexes of polybasic amines
Inorganica Chimica Acta, 2006
The reactions of RuCl 2 [P(C 6 H 5) 3 ] 3 , RuCl 2 (tmeda) 2 , and RuCl 2 (1,5-COD)(tmeda) with polybasic amines such as pyrazole have been studied. From the phosphine complex, a binuclear complex has been isolated in which one pyrazole has been incorporated, while reactions of the latter two with excess pyrazole lead to the replacement of a tmeda ligand by two pyrazoles.
Catalysts
The [Ru(PPh3)2Cl-piperidine(4-aminomethyl)] complex (mono-Ru) was synthesized from [Ru(PPh3)3Cl2] and 4-(aminomethyl)piperidine, whereas the [(PPh3)PdCl(Shiff-pip)] complex (mono-Pd) was obtained by reacting [Pd(PPh3)2Cl2] with its respective Schiff base ligand, both at a 1:1 molar ratio. The heterobimetallic [RuCl2(PPh3)2](μ-Schiff)Pd(PPh3)Cl] complex (Ru/Pd) was synthesized via a one-pot, three-component reaction of mono-Ru, [(Pd(PPh3)2Cl2] and salicylaldehyde. All complexes were fully characterized by FTIR, UV-Vis, and NMR spectroscopy, as well as elemental analysis, MALDI-TOF mass spectrometry, cyclic voltammetry, and computational studies. Ru/Pd was able to polymerize norbornene (NBE) by two different mechanisms: ROMP and vinyl polymerization. The Ru fragment was active for ROMP of NBE, reaching yields of 68 and 31% for mono-Ru and Ru/Pd, respectively, when the [NBE]/[Ru] = 3000 molar ratio and 5 μL EDA addition were employed at 50 °C. The poly(norbornene) (polyNBE) obtained pr...
Journal of Molecular Structure, 2019
A series of [RuCl(dppb)(m-Cl) 3 Ru(dppb)(amine)] complexes, where amine is pyrrolidine (1), piperidine (2) or perhydroazepine (3), were synthesized and characterized by elemental analysis, FTIR, UVeVis, and 1 H, 13 C{ 1 H} and 31 P{ 1 H} NMR spectroscopy. The electrochemistry properties of the complexes 1e3 were investigated by cyclic voltammetry and exhibited two successive single-electron oxidation processes. The presence of two redox pairs suggests the formation of a dimeric species in which two different fragments, {Ru(amine)(dppb)} and {RuCl(dppb)}, were connected via three m-chloro bridges. The complexes 1e3 were evaluated as catalytic precursors for ROMP of norbornene (NBE) and norbornadiene (NBD), as well as for ATRP of methyl methacrylate (MMA). The polynorbornene (polyNBE) syntheses via ROMP using the complexes 1e3 as pre-catalysts were assessed under reaction conditions of [EDA]/[Ru] ¼ 28 (5 mL) and [NBE]/[Ru] ¼ 5000 as a function of time at 25 or 50 C. Polymerization of MMA via ATRP was conducted using the complexes 1e3 in the presence of ethyl 2-bromoisobutyrate (EBiB) as initiator. Differences in the catalytic activities and polymerization controls were observed in the order 3 > 2 > 1 for both reactions. The activities were discussed considering the steric hindrance and electronic characteristics of the amines as ancillary ligands in the metal center using cyclic voltammetry and NMR studies.
Preparation and characterization of RuCl3 – Diamine group functionalized polymer
Reactive and Functional Polymers, 2010
Gel-type resin with diamine functional groups, FCN, was used as a matrix for immobilization of ruthenium complexes. By reacting of RuCl 3 with swollen matrix of FCN polymer a series of Ru/FCN composites with various Ru loading (1%, 2%, and 4%) was prepared. All the characterization techniques (FT-IR, XRD, SEM, EDS, STEM, XPS, and DSC) proved the participation of functional groups in the coordination of Ru(III). These complexes contained both Cl-and N-ligands in various proportions depending on ruthenium loading in polymer. Taking into account the chelating character of N-ligands a hypothetical structure of octahedral Ru(III) complex coordinated to FCN polymer was proposed. 2%Ru/FCN when reduced by NaBH 4 exhibited catalytic activity in liquid phase hydrogenation of acetophenone. Higher selectivity in the presence of FCN supported Ru as compared to 2%Ru/Al 2 O 3 catalyst toward 1-phenylethanol was observed.
Preparation characterization and catalytic activity of polymer supported Ru(III) complexes
Journal of Molecular Catalysis A-chemical, 1996
Chloromethylated styrene-divinyl benzene copolymer with different types of cross-link was treated with glycine for the introduction of the ligand. The polymer modified with ligand was kept in contact with RuCl 3 to form the metal complex on the surface of the polymer. The catalysts thus prepared were characterised by techniques such as IR, UV-Vis reflectance spectroscopy and DTA-TG analysis. Other physico-chemical properties such as surface area, moisture content, bulk density and swelling were also studied. The morphology of the catalysts was observed by scanning electron microscope. The catalysts were tested for the hydrogenation of nitrobenzene as a model reaction. The influence of various parameters such as concentration of catalyst and substrate, temperature and different solvents on the rate of the reaction has been studied.
Journal of Organometallic Chemistry, 2005
The two new complexes [Ru(g 6 -p-cymene)(j 1 -N-(rac)-phenylglycine methylester)Cl 2 ] (1) and [Ru(g 6 -p-cymene)(j 2 -N,N 0 -(S)-phenylalanineamido)Cl] (2) have been synthesized by reacting [Ru(p-cymene)Cl 2 ] 2 with the HCl-free corresponding ligands. The complexes have been fully characterized by spectroscopic and analytical methods, and their solid structures have been determined by single crystal X-ray analysis. Both complexes have a pseudo-tetrahedral geometry: in 1 ruthenium is bound to the nitrogen, to the g 6 -coordinated p-cymene molecule and to two chloride ligands. In 2 the ligand has lost an amide proton binding ruthenium in a N,N 0 bidentate fashion, the coordination geometry being completed by a g 6 -coordinated p-cymene molecule and a chloride ligand. The X-ray structure of 1 has revealed the racemization of the ligand, while in 2 the ligand has retained its configuration but, interestingly, the two diasteromers R Ru S C and S Ru S C have co-crystallized in the same single crystal. The crystal architecture of 2 is characterized by the presence of two opposite helices of akin diastereoisomers, connected through strong intermolecular hydrogen bonds between the amine and carbonyl groups. ESI-MS of an i-PrOH solution of 2 points out that the dimers are maintained also in solution. Complex 2 is an active catalyst for the homogeneous transfer hydrogenation of acetophenone and cyclohexanone in an i-PrOH/t-BuOK mixture, with TOFs up to 800 and 1000 h À1 , respectively.
Benefits of donor solvents as additive on ROMP of norbornene catalyzed by amine Ru complexes
Journal of Molecular Catalysis A: Chemical, 2005
With the aim of understanding the influence of donor solvents on the reactivity of the amine complexes [RuCl 2 (PPh 3) 2 (piperidine)] (1) and [RuCl 2 (PPh 3) 2 (imidazole) 2 ] (2) in the presence of ethyldiazoacetate, and on the properties of the resulting polymer, a ring opening metathesis polymerization of norbornene was carried out in the presence of small amounts of common solvents such as additives (isopropanol, THF, N,N-dimethylformamide, 2,6-lutidine, isopropanethiol, acetonitrile, dimethyl sulfoxide, NEt 3 , NH 2 Me and pyridine). From observations, typical coordinating solvents like DMSO, NEt 3 , NH 2 Me and pyridine, hardly affected the yields when either complex was employed. With other additives, the major advantage was the decrease in the polydispersity indices. On using complex 1 with 2,6-lutidine, observed values of M w /M n were as low as 1.3, while the yield decreased from 99% to about 20-30% at RT for ∼1 min in pure solution. In the case of complex 2, which is almost inactive to ROMP (19% at 50 • C for 5 min with M w /M n = 6.30), the yield was threefold (60% at 50 • C for 5 min with M w /M n = 1.95) compared to that of without THF. Further, the M w /M n was observed to decrease to 1.34 with 200 eq. of THF.