01382nas a2200169 4500008004100000245008000041210006900121260000800190300001800198490000800216520078100224100002501005700002801030700002501058700002001083856010901103 2010 eng d00aDirect hydrogenation of amides to alcohols and amines under mild conditions0 aDirect hydrogenation of amides to alcohols and amines under mild cNOV a16756–167580 v1323 a

The selective, direct hydrogenation of amides to the corresponding alcohols and amines with cleavage of the C−N bond was discovered. The expected products of C−O cleavage are not formed (except as traces in the case of anilides). The reaction proceeds under mild pressure and neutral, homogeneous conditions using a dearomatized, bipyridyl-based PNN Ru(II) pincer complex as a catalyst. The postulated mechanism involves metal−ligand cooperation by aromatization−dearomatization of the heteroaromatic pincer core and does not involve hydrolytic cleavage of the amide. The simplicity, generality, and efficiency of this environmentally benign process make it attractive for the direct transformations of amides to alcohols and amines in good to excellent yields.

1 aBalaraman, Ekambaram1 aGnanaprakasam, Boopathy1 aShimon, Linda, J. W.1 aMilstein, David uhttps://library.ncl.res.in/content/direct-hydrogenation-amides-alcohols-and-amines-under-mild-conditions01850nas a2200181 4500008004100000245013700041210006900178260000800247300001400255490000600269520115100275100002501426700002801451700001601479700002501495700002001520856012801540 2011 eng d00aEfficient hydrogenation of organic carbonates, carbamates, and formates indicates alternative routes to methanol based on CO2 and CO0 aEfficient hydrogenation of organic carbonates carbamates and for cJUL a609–6140 v33 a

Catalytic hydrogenation of organic carbonates, carbamates and formates is of significant interest both conceptually and practically, because these compounds can be produced from CO2 and CO, and their mild hydrogenation can provide alternative, mild approaches to the indirect hydrogenation of CO2 and CO to methanol, an important fuel and synthetic building block. Here, we report for the first time catalytic hydrogenation of organic carbonates to alcohols, and carbamates to alcohols and amines. Unprecedented homogeneously catalysed hydrogenation of organic formates to methanol has also been accomplished. The reactions are efficiently catalysed by dearomatized PNN Ru(II) pincer complexes derived from pyridine- and bipyridine-based tridentate ligands. These atom-economical reactions proceed under neutral, homogeneous conditions, at mild temperatures and under mild hydrogen pressures, and can operate in the absence of solvent with no generation of waste, representing the ultimate ‘green’ reactions. A possible mechanism involves metal–ligand cooperation by aromatization–dearomatization of the heteroaromatic pincer core.

1 aBalaraman, Ekambaram1 aGunanathan, Chidambaram1 aZhang, Jing1 aShimon, Linda, J. W.1 aMilstein, David uhttps://library.ncl.res.in/content/efficient-hydrogenation-organic-carbonates-carbamates-and-formates-indicates-alternative02558nas a2200169 4500008004100000245018200041210006900223260000800292300001600300490000700316520185500323100001602178700002502194700002002219700002002239856012902259 2011 eng d00aElectron-rich PNP- and PNN-type Ru(II) hydrido-borohydride complexes. synthesis, structure and catalytic activity towards dehydrogenation of alcohols and hydrogenation of esters0 aElectronrich PNP and PNNtype RuII hydridoborohydride complexes s cOCT a5716–57240 v303 a

Electron-rich PNP- and PNN-type ruthenium(II) hydrido borohydride pincer complexes, [RuH(BH4)(tBu-PNP)] (tBu-PNP = (2,6-bis(di-tert-butylphosphinomethyl)pyridine) (5) and [RuH(BH4)(tBu-PNN)] (tBu-PNN = 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) (6), were prepared from their corresponding N2-bridged dinuclear Ru(II) complexes [(tBu-PNP)RuCl2]2(μ-N2) (3) and [(tBu-PNN)RuCl2]2(μ-N2) (4), respectively. The X-ray structure of 5 reveals a BH4– anion η2 coordinated to ruthenium through two bridging hydrides. A variable-temperature 1H NMR study of 6 exhibits interesting fluxional behavior of the BH4– ligand. Similarly, the Ru(II) hydrido borohydride complex 9, in which the BH4– moiety is coordinated in a η1 bonding mode, was obtained by reaction of [RuCl2(PPh3)(iPr-PNP)] (iPr-PNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) (8) with two equivalents of NaBH4 at room temperature. The hydrido borohydride pincer complexes 5, 6, and 9 catalyze the acceptorless dehydrogenative coupling of primary alcohols to esters and the dehydrogenation of secondary alcohols to the corresponding ketones, accompanied by evolution of hydrogen gas. The reactivity follows the order 6 > 9 > 5. With the hydrido borohydride complex 6 as catalyst, high yields (up to 98%) and high turnover numbers (TON ∼1000) were obtained in the dehydrogenation of primary alcohols under mild and neutral conditions. In addition, 6 effectively catalyzes the hydrogenation of nonactivated aromatic and aliphatic esters to the corresponding alcohols with TON ∼200 under a relatively mild pressure of dihydrogen and neutral and homogeneous conditions. Thus, an efficient homogeneous catalytic system for the dehydrogenation–hydrogenation reactions of alcohols is developed, which is relevant to the current interest in hydrogen storage.

1 aZhang, Jing1 aBalaraman, Ekambaram1 aLeitus, Gregory1 aMilstein, David uhttps://library.ncl.res.in/content/electron-rich-pnp-and-pnn-type-ruii-hydrido-borohydride-complexes-synthesis-structure-and02571nas 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-methanol00902nas a2200157 4500008004100000245007700041210006900118260000800187300001400195490000700209520036100216100002500577700001700602700002000619856010500639 2012 eng d00aEfficient hydrogenation of biomass derived cyclic di-esters to 1,2-diols0 aEfficient hydrogenation of biomass derived cyclic diesters to 12 cOCT a1111-11130 v483 a

The unprecedented homogeneous hydrogenation of cyclic di-esters, in particular biomass-derived glycolide and lactide, to the corresponding 1,2-diols is catalyzed by Ru(II) PNN (1) and Ru(II) CNN (2) pincer complexes under mild hydrogen pressure and (in the case of 1) neutral conditions. No racemization was observed when a chiral di-ester was used.

1 aBalaraman, Ekambaram1 aFogler, Eran1 aMilstein, David uhttps://library.ncl.res.in/content/efficient-hydrogenation-biomass-derived-cyclic-di-esters-12-diols01874nas a2200157 4500008004100000245013500041210006900176260000800245520121900253100002001472700002501492700002801517700002801545700001601573856012701589 2012 eng d00aNovel ruthenium complexes and their uses in processes for formation and/or hydrogenation of esters, amides and derivatives thereof0 aNovel ruthenium complexes and their uses in processes for format cOCT3 a

The present invention relates to novel Ruthenium complexes and related borohydride complexes, and their use for (1) hydrogenation of amides (including polyamides) to alcohols and amines; (2) preparing amides from alcohols with amines (including preparing polyamides (e.g., polypeptides) by reacting dialcohols and diamines or by polymerization of amino alcohols); (3) hydrogenation of esters to alcohols (including hydrogenation of cyclic esters (lactones), cyclic di-esters (di-lactones) or polyesters); (4) hydrogenation of organic carbonates (including polycarbonates) to alcohols and of carbamates (including polycarbamates) or urea derivatives to alcohols and amines; (5) dehydrogenative coupling of alcohols to esters; (6) hydrogenation of secondary alcohols to ketones; (7) amidation of esters (synthesis of amides from esters and amines); (8) acylation of alcohols using esters; (9) coupling of alcohols with water to form carboxylic acids; and (10) dehydrogenation of beta-amino alcohols to form pyrazines. The present invention further relates to novel uses of certain pyridine Ruthenium complexes.

1 aMilstein, David1 aBalaraman, Ekambaram1 aGunanathan, Chidambaram1 aGnanaprakasam, Boopathy1 aZhang, Jing uhttps://library.ncl.res.in/content/novel-ruthenium-complexes-and-their-uses-processes-formation-andor-hydrogenation-esters00981nas 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-secondary02002nas 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-h201646nas 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-acid01390nas a2200169 4500008004100000245011100041210006900152260000800221300001400229490000600243520076000249100002501009700002001034700002001054700002001074856012601094 2013 eng d00aCatalytic transformation of alcohols to carboxylic acid salts and H2 using water as the oxygen atom source0 aCatalytic transformation of alcohols to carboxylic acid salts an cFEB a122–1250 v53 a

The oxidation of alcohols to carboxylic acids is an important industrial reaction used in the synthesis of bulk and fine chemicals. Most current processes are performed by making use of either stoichiometric amounts of toxic oxidizing agents or the use of pressurized dioxygen. Here, we describe an alternative dehydrogenative pathway effected by water and base with the concomitant generation of hydrogen gas. A homogeneous ruthenium complex catalyses the transformation of primary alcohols to carboxylic acid salts at low catalyst loadings (0.2 mol%) in basic aqueous solution. A consequence of this finding could be a safer and cleaner process for the synthesis of carboxylic acids and their derivatives at both laboratory and industrial scales.

1 aBalaraman, Ekambaram1 aKhaskin, Eugene1 aLeitus, Gregory1 aMilstein, David uhttps://library.ncl.res.in/content/catalytic-transformation-alcohols-carboxylic-acid-salts-and-h2-using-water-oxygen-atom01291nas 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-amines02343nas a2200193 4500008004100000245016200041210006900203260000800272300001600280490000700296520155600303100003301859700002501892700002401917700002001941700002501961700002001986856014302006 2013 eng d00aPNN-Ru pincer complexes based on phosphinated 2,2’-dipyridinemethane- and 2,2’-oxobispyridine. metal-ligand cooperation in cyclometallation and catalysis0 aPNNRu pincer complexes based on phosphinated 22 dipyridinemethan cMAY a2973–29820 v323 a

The synthesis of novel PNN ruthenium pincer complexes based on 2,2′-dipyridinemethane phosphine derivatives, as well as on 2,2′-oxobispyridine phosphine ligands, and their reactivity toward dearomatization and cyclometalation are described. The dearomatized compounds 7a,b undergo cyclometalation to yield complexes 8a,b. In order for cyclometalation to proceed, the coordination sphere around the Ru center has to rearrange, and this depends on the flexibility of the system, showing that the cyclometalation is qualitatively faster in the case of the dimethyl derivative 7a than in the case of the spyrocyclopentyl derivative 7b. The cyclometalation occurs diastereoselectively and leads to only one diastereomer of the cyclometalated compounds. In the case of the 2,2′-oxobispyridine complex 6c, the dearomatized complex was too unstable to be isolated; however it was possible to isolate and characterize a stable dicarbonyl-dearomatized ruthenium(II) complex, 9c, when the deprotonation was performed under a CO atmosphere. Dearomatization of 6a under CO also led to dicarbonyl-dearomatized ruthenium(II) complex 9a, which slowly rearranged into the dicarbonyl-aromatized ruthenium(0) complex 10a. These complexes were tested in catalytic alcohol–amine coupling, esterification of primary alcohols, and hydrogenation of secondary amides. Moderate activity was observed in hydrogenation of amides to alcohols and amines and low activity in the other transformations, owing mainly to the formation of stable cyclometalated compounds.

1 aBarrios-Francisco, Rigoberto1 aBalaraman, Ekambaram1 aDiskin-Posner, Yael1 aLeitus, Gregory1 aShimon, Linda, J. W.1 aMilstein, David uhttps://library.ncl.res.in/content/pnn-ru-pincer-complexes-based-phosphinated-22%E2%80%99-dipyridinemethane-and-22%E2%80%99-oxobispyridine01807nas 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-bipyridine02120nas a2200289 4500008004100000020004100041022001400082245007300096210006900169260026000238300001000498490000700508520099400515653001101509653001901520653001101539653001301550653001801563653002901581653002101610653001401631100002501645700002001670700001601690700002001706856010401726 2014 eng d a978-3-319-08482-4; 978-3-319-08481-7 a1436-600200aHydrogenation of polar bonds catalysed by ruthenium-pincer complexes0 aHydrogenation of polar bonds catalysed by rutheniumpincer comple aHEIDELBERGER PLATZ 3, D-14197 BERLIN, GERMANYbIEEE Commun Soc; IEEE Syst Man & Cybernet Soc; Galgotias Coll Engn & Technol; Hochschule Offenburg Univ Appl Sci; Int Neural Network Soc; India Chapter & Res Publishing Serv; Madhyam; WizIQ; ICACCI; IEEEcMAR a19-430 v483 a

Catalytic hydrogenation of polar bonds using molecular hydrogen is an important, atom-economical synthetic reaction. Classical reduction methods of polar bond often require reactive metal-hydride reagents in stoichiometric amount and produce copious waste. Hydrogenation of carbonyl compounds in particular provides `green' approaches to synthetically important building blocks, such as alcohols and amines. We have designed and synthesized several ruthenium-based pincer catalysts for unprecedented hydrogenation reactions including: (1) amides to alcohols and amines, (2) biomass-derived di-esters to 1,2-diols and (3) CO2 and CO derivatives to methanol. These atom-economical reactions operate under neutral, homogeneous conditions, at mild temperatures, mild hydrogen pressures, and can operate in absence of solvent with no generation of waste. The postulated mechanisms involve metal-ligand cooperation (MLC) by aromatization-dearomatization of the heteroaromatic pincer core.

10aAmides10aCarbon dioxide10aEsters10aHydrogen10aHydrogenation10aMetal-ligand cooperation10aPincer complexes10aruthenium1 aBalaraman, Ekambaram1 aMilstein, David1 aBruneau, C.1 aDixneuf, P., H. uhttps://library.ncl.res.in/content/hydrogenation-polar-bonds-catalysed-ruthenium-pincer-complexes-001285nas a2200241 4500008004100000022001400041245010700055210006900162260005700231300001200288490000800300520042200308653001200730653001200742653002500754653002200779653002000801100002500821700002200846700002400868700002000892856013100912 2015 eng d a1011-372X00aDirect synthesis of secondary amines from alcohols and ammonia catalyzed by a ruthenium pincer complex0 aDirect synthesis of secondary amines from alcohols and ammonia c a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcJAN a139-1440 v1453 a

Efficient and selective direct synthesis of secondary amines from primary alcohols and ammonia with liberation of water has been achieved, with high turnover numbers and with no generation of waste. In case of benzylic alcohols, imines rather than amines are obtained. This atom economical, environmentally benign reaction is homogenously catalyzed by a well-defined bipyridine based Ru(II)-PNN pincer complex.

10aAlcohol10aAmmonia10aHomogenous catalysis10aRu-pincer complex10aSecondary amine1 aBalaraman, Ekambaram1 aSrimani, Dipankar1 aDiskin-Posner, Yael1 aMilstein, David uhttps://library.ncl.res.in/content/direct-synthesis-secondary-amines-alcohols-and-ammonia-catalyzed-ruthenium-pincer-complex-0