02570nas a2200193 4500008004100000245012300041210006900164260000800233300001600241490000700257520185100264100001702115700002502132700002402157700002002181700002502201700002002226856013002246 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 uhttp://library.ncl.res.in/content/new-cnn-type-ruthenium-pincer-nhc-complexes-synthesis-and-catalytic-activity-mild-efficient01873nas a2200157 4500008004100000245013500041210006900176260000800245520121900253100002001472700002501492700002801517700002801545700001601573856012601589 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 uhttp://library.ncl.res.in/content/novel-ruthenium-complexes-and-their-uses-processes-formation-andor-hydrogenation-esters