02571nas a2200193 4500008004100000245012300041210006900164260000800233300001600241490000700257520185100264100001702115700002502132700002402157700002002181700002502201700002002226856013102246 2011 eng d00aNew CNN-type ruthenium pincer NHC complexes. synthesis and catalytic activity. mild, efficient hydrogenation of esters0 aNew CNNtype ruthenium pincer NHC complexes synthesis and catalyt cJUN a3826–38330 v303 a

New pincer ruthenium complexes (2–6) based on the new bipyridine-NHC ligand 1 were prepared and studied, resulting in an efficient catalytic hydrogenation of esters to the corresponding alcohols under mild conditions. Reaction of the ligand 1 with RuH(Cl)CO(PPh3)3, followed by reaction with one equivalent of the base KHMDS, gave the mixed phosphine-NHC complex 2, incorporating a C–H-activated bipyridine ligand. Complex 2 has an octahedral structure containing two phosphorus atoms trans to each other, a hydride trans to the NHC ligand, and CO trans to the C–H-activated carbon of the bipyridine ligand. Using the precursor complex Ru(p-cymene)Cl2(CO), reaction with 1 followed by treatment of the intermediate product with one equivalent of KHMDS resulted in formation of the dichloride pincer complexes 3a and 3b, which are in equilibrium, as indicated by variable-temperature 1H NMR. Complex 3a is an octahedral, neutral, and symmetric complex with the CO ligand positioned trans to the central pyridine group of the pincer ligand and the two chlorides trans to each other, as indicated by single-crystal X-ray diffraction. Complex 3b is cationic, with an outer-sphere chloride. Reaction of the NHC ligand 1 with LiHMDS at low temperature followed by addition of RuH(Cl)CO(PPh3)3 resulted in the mixed phosphine-NHC complex 4, which has an octahedral structure containing phosphorus trans to the hydride, a CO trans to the NHC ligand, and an outer-sphere chloride. Chloride substitution by BArF– gave the X-ray-characterized complex 5. Deprotonation of complex 4 with KHMDS resulted in formation of the dearomatized complex 6. The in situ prepared 6 (from complex 4 and an equivalent of base) is among the best catalysts known for the hydrogenation of nonactivated esters to the corresponding alcohols under mild conditions.

1 aFogler, Eran1 aBalaraman, Ekambaram1 aBen-David, Yehoshoa1 aLeitus, Gregory1 aShimon, Linda, J. W.1 aMilstein, David uhttps://library.ncl.res.in/content/new-cnn-type-ruthenium-pincer-nhc-complexes-synthesis-and-catalytic-activity-mild-efficient01100nas 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-pincer01003nas a2200157 4500008004100000245008500041210006900126260000800195300001800203490000800221520043300229100002500662700002400687700002000711856011400731 2011 eng d00aUnprecedented catalytic hydrogenation of urea derivatives to amines and methanol0 aUnprecedented catalytic hydrogenation of urea derivatives to ami cDEC a11906–119090 v1233 a

Indirekte CO2-Hydrierung: Eine Hydrierung von Harnstoffen zu Aminen und Methanol (siehe Bild) wird durch einen RuII-Pinzettenkomplex mit dreizähnigem bipyridinbasiertem PNN-Liganden katalysiert und verläuft unter milden, neutralen Bedingungen bei einem H2-Druck von 13.6 atm. Da sich Harnstoffderivate ausgehend von CO2 erhalten lassen, ermöglicht dieser Ansatz die indirekte Hydrierung von Kohlendioxid zu Methanol.

1 aBalaraman, Ekambaram1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/unprecedented-catalytic-hydrogenation-urea-derivatives-amines-and-methanol00981nas a2200181 4500008004100000245013100041210006900172260000800241300001600249490000800265520028300273100002200556700002500578700002800603700002400631700002000655856012400675 2012 eng d00aRuthenium pincer-catalyzed cross-dehydrogenative coupling of primary alcohols with secondary alcohols under neutral conditions0 aRuthenium pincercatalyzed crossdehydrogenative coupling of prima cSEP a2403–24060 v3543 a

Cross-dehydrogenative coupling of primary alcohols with secondary alcohols to obtain mixed esters with the liberation of molecular hydrogen is achieved in high yield and good selectivity under neutral conditions, using a bipyridyl-based PNN ruthenium(II) pincer catalyst.

1 aSrimani, Dipankar1 aBalaraman, Ekambaram1 aGnanaprakasam, Boopathy1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/ruthenium-pincer-catalyzed-cross-dehydrogenative-coupling-primary-alcohols-secondary01646nas a2200169 4500008004100000245011600041210006900157260000800226520097300234100002001207700002801227700002401255700002501279700002801304700001601332856012801348 2012 eng d00aUse of ruthenium complexes for formation and/or hydrogenation of amides and related carboxylic acid derivatives0 aUse of ruthenium complexes for formation andor hydrogenation of  cMAR3 a

A process for preparing amides by reacting a primary amine and a primary alcohol in the presence of a Ruthenium complex to generate the amide and molecular hydrogen. Primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only byproduct) in high yields and high turnover numbers. Also disclosed are processes for hydrogenation of amides to alcohols and amines; hydrogenation of organic carbonates to alcohols; hydrogenation of carbamates or urea derivatives to alcohols and amines; amidation of esters; acylation of alcohols using esters; coupling of alcohols with water and a base to form carboxylic acids; dehydrogenation of beta-amino alcohols to form pyrazines and cyclic dipeptides; and dehydrogenation of secondary alcohols to ketones. These reactions are catalyzed by a Ruthenium complex which is based on a dearomatized PNN-type ligand of formula A1 or precursors thereof of formulae A2 or A3.

1 aMilstein, David1 aGunanathan, Chidambaram1 aBen-David, Yehoshoa1 aBalaraman, Ekambaram1 aGnanaprakasam, Boopathy1 aZhang, Jing uhttps://library.ncl.res.in/content/use-ruthenium-complexes-formation-andor-hydrogenation-amides-and-related-carboxylic-acid01291nas a2200181 4500008004100000245016700041210006900208260000800277300001600285490000800301520056500309100002200874700002500896700001300921700002400934700002000958856013100978 2013 eng d00aFormation of tertiary amides and H2 by dehydrogenative coupling of primary alcohols with secondary amines catalyzed by ruthenium bipyridine-based pincer complexes0 aFormation of tertiary amides and H2 by dehydrogenative coupling  cSEP a2525–25300 v3553 a

Dehydrogenative coupling of primary alcohols with secondary amines to form tertiary amides and dihydrogen (H2) is efficiently catalyzed by bipyridyl-based ruthenium pincer complexes (0.2–1 mol%) under neutral conditions (in case of the dearomatized complexes), or with added catalytic amount of base. The reaction is sensitive to steric hindrance; in the case of amidation of bulky secondary amines a less sterically hindered complex is more efficient. Selective acylation of primary amines in the presence of secondary amines was also demonstrated.

1 aSrimani, Dipankar1 aBalaraman, Ekambaram1 aHu, Peng1 aBen-David, Yehoshoa1 aMilstein, David uhttps://library.ncl.res.in/content/formation-tertiary-amides-and-h2-dehydrogenative-coupling-primary-alcohols-secondary-amines01807nas 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