The ring size of cyclic amines as relevant feature in the activity of Ru-based complexes for ROMP (original) (raw)
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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.
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...
A Chloro-Bridged (Arene)Ru Complex with a Polymerizable Side Chain
Organometallics, 2003
An [(arene)RuCl 2 ] 2 complex with a methacrylate side chain (2) has been prepared in two steps using commercially available starting materials. This complex reacts with PPh 3 , pyridine, or toluidine to give the corresponding mononuclear adducts (3-5). The structure of 4 was determined by single-crystal X-ray diffraction. Complex 2 and the PPh 3 adduct 3 were immobilized by copolymerization with divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA). The resulting EGDMA copolymer was tested as a catalyst in asymmetric transfer hydrogenations. Using (1R,2R)-(-)-N-p-tosyl-1,2-diphenylethylenediamine as the chiral ligand and azeotropic NEt 3 /HCO 2 H as the reducing agent, aromatic ketones were converted to the corresponding alcohols with selectivities between 87 and 97% ee.
Organometallics, 2014
The complex [RuCl(Tp)(1,5-cod)], which bears the labile 1,5-cod ligand, was prepared from a high-yielding route involving the reaction of [RuCl 2 (1,5-cod)(CH 3 CN) 2 ] with KTp (Tp = HB(pz) 3 ). The reaction of [RuCl(Tp)(1,5-cod)] with phenylacetylene in either ethanol or methanol gave anti-Markovnikov alkoxide-adduct complexes [Ru(Tp)(η 6 -C 5 H 2 Ph 2 -CH(Ph)R)] (R = OMe, OEt). These adducts were formed by [2 + 2 + 1] cyclotrimerization reactions of phenylacetylene mediated by the precursor complex, [RuCl(Tp)(1,5cod)]. The ruthenium(II)−fulvene complex, [Ru(Tp)(η 6 -C 5 H 2 Ph 2 -CH(Ph))] + , involved in these transformations was successfully isolated in the presence of NH 4 PF 6 . These complexes were fully characterized by 1 H NMR, 13 C NMR, DEPT, HSQC, IR, and ESI-MS spectroscopy. The molecular structures of [Ru(Tp)(η 6 -C 5 H 2 Ph 2 -CH(Ph)R)] (R = OMe/OEt) and [Ru(Tp)(η 6 -C 5 H 2 Ph 2 -CH(Ph))]PF 6 have been determined by X-ray single-crystal diffraction. These complexes have piano-stool structures around the ruthenium center where half of the coordination sites are occupied by the pyrazole ligand while the remaining sites are occupied by either the π-bonded cyclopentadiene (Cp) or fulvene ligand.
Polyhedron, 2002
The di-arylamino complex [RuCl 2 (ArNH 2) 2 L] (ArNH 2 = aromatic monoamine and L = N-aryl-1,2-diimino arene) reacts spontaneously with aqueous H 2 O 2 to produce two isomers of [RuCl 2 (L) 2 ] via oxidative dimerization of the two coordinated aromatic amines. The geometries of two isomers are cis with respect to two chlorides and are trans, cis(tc) and cis, cis(cc) in the following sequence: NH(imine), HN(imine) and ArN(imine), ArN(imine). Of the above two, the tc-[RuCl 2 (L) 2 ] forms good X-ray quality crystals. The structure of a representative has been solved by X-ray diffraction. The geometry of the cc-[RuCl 2 (L) 2 ] is, however, revealed by the spectral data. The tc-isomer possesses a C 2-symmetry axis and the two-coordinated diimine ligands are magnetically equivalent. As a result, a single NH resonance in tc-[RuCl 2 (L) 2 ] appeared at approximately l 12.40. By contrast, the cc-isomer is unsymmetrical and a complex pattern of 1 H NMR was observed in this case. Thus, there were two NH resonances observed in the range approximately l 14.11-11.88. A semi-empirical extended Hü ckel MO calculations on a representative example showed strong metal-ligand overlap. A highly intense electronic transition that appeared in the visible range spectra of the complexes was assigned to a transition involving two molecular orbitals with considerable metal and ligand contributions. Both the isomers of the complex showed a high potential anodic response (0.8 V) due to the Ru III /Ru II couple. The trivalent congeners [RuCl 2 (L) 2 ] + were generated in solution which showed characteristic rhombic EPR for the low spin d 5 ions. The distortion parameters have been computed using the observed g values. The axial distortion (D) in each case is found to be stronger than the rhombic (V) distortion.
In this investigation we applied the Density Functional Theory to understand the substituent effects of cyclic and acyclic amines on the stability of RuCl2(PPh3)2 (amine) complexes. In order to evaluate the relative stability of each complex, we analyzed five conformations considering different positions of the chlorine atoms and the triphenylphosphine ligand: a cis–cis (1), a trans–trans (2), a trans–cis (3), a cis–cis (4) and a cis–trans configuration (5). In addition, eight different amine ligands were considered: two acyclic (ammonia and trimethylamine), two cyclic aliphatic (piperidine and pyrrolidine) and four aromatic amine ligands (pyridine, pyrazine, pyrimidine and pyridazine). All the structures presented a square pyramid geometry, and in all systems the stereoisomer 3 is the most stable arrangement among the five isomers. Among the complexes with cyclic aliphatic amine ligands, the energy gap between arrangements 2 and 3 are the most sensitive to the substituent change. Furthermore, when it is considered the replacement by an aromatic amine, there are a large decrease in the energy difference between the arrangements 2 and 3.