01100nas a2200169 4500008004100000245015500041210006900196260000800265300001800273490000800291520040300299100002800702700002500730700002400755700002000779856013100799 2011 eng d00aSynthesis of peptides and pyrazines from beta-aminoalcohols via extrusion of H2 catalyzed by ruthenium pincer complexes. ligand controlled selectivity0 aSynthesis of peptides and pyrazines from betaaminoalcohols via e cOCT a12448–124520 v1233 a

Bitte wählen: Die Wahl des Katalysators, eines Ru-Pinzettenkomplexes, bestimmt, ob Peptide oder Pyrazine aus β-Aminoalkoholen entstehen: Der PNN-Komplex 1 führt, je nach Substituent R (siehe Schema), zu linearem Polyalanin oder zu cyclischen Dipeptiden, der PNP-Komplex 2 katalysiert die Bildung von Pyrazinen. Die Reaktionen finden in homogener Lösung unter neutralen Bedingungen statt.

1 aGnanaprakasam, Boopathy1 aBalaraman, Ekambaram1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/synthesis-peptides-and-pyrazines-beta-aminoalcohols-extrusion-h2-catalyzed-ruthenium-pincer02002nas a2200169 4500008004100000245007400041210006900115260000800184300001600192490000700208520142300215100002801638700002501666700002801691700002001719856009301739 2012 eng d00aSynthesis of polyamides from diols and diamines with liberation of H20 aSynthesis of polyamides from diols and diamines with liberation  cMAY a1755–17650 v503 a

The amidation reaction based on catalytic coupling of alcohols with amines previously reported by us, using the pincer complexes 1 and 2 as catalysts, was applied to the generation of polyamides from nonactivated diols and diamines. A range of polymers was prepared, with Mn up to 26.9 kDa. Unlike the traditional syntheses of polyamides based on carboxylic acid derivatives, which require the use of toxic reagents and generate stoichiometric amounts of waste, this process generates only molecular hydrogen as byproduct. Both aromatic and aliphatic diols and diamines were used. Gel permeation chromatography measurements of the dimethylformamide-soluble polymers and thermal studies of the polyamides were performed. Matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectra are also reported. Thermogravimetric analyses studies indicate that the aromatic polyamides (with the exception of the pyridine-based polyamide) are more thermally stable than the aliphatic ones. This general, environmentally benign method for the synthesis of polyamides is homogeneously catalyzed under neutral conditions by dearomatized ruthenium-pincer complexes 1 and 2 and proceeds in 1,4-dioxane under an inert atmosphere. Conditions for polyamidation in the absence of solvent are also reported, using the pincer complex 2 as catalyst. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

1 aGnanaprakasam, Boopathy1 aBalaraman, Ekambaram1 aGunanathan, Chidambaram1 aMilstein, David uhttps://library.ncl.res.in/content/synthesis-polyamides-diols-and-diamines-liberation-h201807nas a2200217 4500008004100000245016300041210006900204260000800273300001600281490000700297520098300304100001901287700001501306700001901321700002501340700002401365700002501389700002401414700002001438856013101458 2013 eng d00aStepwise metal-ligand cooperation via a reversible aromatization-deconjugation-sequence in ruthenium complexes with a tetradentate phenanthroline-based ligand0 aStepwise metalligand cooperation via a reversible aromatizationd cMAR a3407–34140 v193 a

The synthesis and reactivity of ruthenium complexes containing the tetradentate phenanthroline-based phosphine ligand 2,9-bis((di-tert-butylphosphino)methyl)-1,10-phenanthroline (PPhenP) is described. The hydrido chloro complex [RuHCl(PPhenP)] (2) undergoes facile dearomatization upon deprotonation of the benzylic position, to give [RuH(PPhenP-H)] (4). Addition of dihydrogen to 4 causes rearomatization of the phenanthroline moiety to trans-[Ru(H)2(PPhenP)] (5), followed by hydrogenation of an aromatic heterocycle in the ligand backbone, to give a new dearomatized and deconjugated complex [RuH(PPhenP*-H)] (6). These aromatization/deconjugation steps of the coordinated ligand were demonstrated to be reversible and operative in the dehydrogenation of primary alcohols without the need for a hydrogen acceptor. This aromatization/deconjugation sequence constitutes an unprecedented mode of a stepwise cooperation between the metal center and the coordinated ligand.

1 aLanger, Robert1 aFuchs, Ido1 aVogt, Matthias1 aBalaraman, Ekambaram1 aDiskin-Posner, Yael1 aShimon, Linda, J. W.1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/stepwise-metal-ligand-cooperation-reversible-aromatization-deconjugation-sequence-ruthenium02868nas a2200241 4500008004100000245012800041210006900169260000800238300001600246490000700262520200600269100001702275700001902292700001902311700002802330700002502358700002402383700002002407700002502427700002402452700002002476856013002496 2013 eng d00aSynthesis, structures, and dearomatization by deprotonation of iron complexes featuring bipyridine-based PNN pincer ligands0 aSynthesis structures and dearomatization by deprotonation of iro cJUL a9636–96490 v523 a

The synthesis and characterization of new iron pincer complexes bearing bipyridine-based PNN ligands is reported. Three phosphine-substituted pincer ligands, namely, the known tBu-PNN (6-((di-tert-butylphosphino)methyl)-2,2′-bipyridine) and the two new iPr-PNN (6-((di-iso-propylphosphino)methyl)-2,2′-bipyridine) and Ph-PNN (6-((diphenylphosphino)methyl)-2,2′-bipyridine) ligands were synthesized and studied in ligation reactions with iron(II) chloride and bromide. These reactions lead to the formation of two types of complexes: mono-chelated neutral complexes of the type [(R-PNN)Fe(X)2] and bis-chelated dicationic complexes of the type [(R-PNN)2Fe]2+. The complexes [(R-PNN)Fe(X)2] (1: R = tBu, X = Cl, 2: R = tBu, X = Br, 3: R = iPr, X = Cl, and 4: R = iPr, X = Br) are readily prepared from reactions of FeX2 with the free R-PNN ligand in a 1:1 ratio. Magnetic susceptibility measurements show that these complexes have a high-spin ground state (S = 2) at room temperature. Employing a 2-fold or higher excess of iPr-PNN, diamagnetic hexacoordinated dicationic complexes of the type [(iPr-PNN)2Fe](X)2 (5: X = Cl, and 6: X = Br) are formed. The reactions of Ph-PNN with FeX2 in a 1:1 ratio lead to similar complexes of the type [(Ph-PNN)2Fe](FeX4) (7: X = Cl, and 8: X = Br). Single crystal X-ray studies of 1, 2, 4, 6, and 8 do not indicate electron transfer from the FeII centers to the neutral bipyridine unit based on the determined bond lengths. Density functional theory (DFT) calculations were performed to compare the relative energies of the mono- and bis-chelated complexes. The doubly deprotonated complexes [(R-PNN*)2Fe] (9: R = iPr, and 10: R = Ph) were synthesized by reactions of the dicationic complexes 6 and 8 with KOtBu. The dearomatized nature of the central pyridine of the pincer ligand was established by X-ray diffraction analysis of single crystals of 10. Reactivity studies show that 9 and 10 have a slightly different behavior in protonation reactions.

1 aZell, Thomas1 aLanger, Robert1 aIron, Mark, A.1 aKonstantinovski, Leonid1 aShimon, Linda, J. W.1 aDiskin-Posner, Yael1 aLeitus, Gregory1 aBalaraman, Ekambaram1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/synthesis-structures-and-dearomatization-deprotonation-iron-complexes-featuring-bipyridine