02343nas 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<p>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.</p>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-oxobispyridine