Catalytic deoxygenation of terminal-diols under acidic aqueous conditions by the ruthenium complexes [(η 6-arene)Ru(X)(N ∩ N)](OTf) n, X = H 2O, H, η 6-arene = p-Me- iPr-C 6H 4, C 6Me 6, N ∩ N = bipy, phen, 6,6′-diamino-bipy, 2,9-diamino-phen, n = 1, 2) : Influence of the ortho-amine substituents on catalytic activity

Abstract

A series of ruthenium complexes of the general composition [(η 6-arene)(N ∩ N)Ru(X)](Y) n , (arene = p-Me- i Pr-C 6H 4, C 6Me 6; N ∩ N = bipy, phen, 6,6′-diamino-2,2′-bipyridine, 2,9-diamino-1,10-phenanthroline; X = Cl, H, H 2O; Y = Cl, OTf) was synthesized and the new compounds exhaustively structurally characterized by standard techniques (NMR, IR, elemental analysis, single-crystal X-ray crystallography). The single-crystal X-ray structures of [( p-Me- i Pr-C 6H 4)Ru(dabipy)Cl][Cl] ( 3Cl[Cl]), [( p-Me- i Pr-C 6H 4)Ru(daphen)Cl][Cl] ( 4Cl[Cl]), [(C 6Me 6)Ru(dabipy)Cl][Cl] ( 7Cl[Cl]), [(C 6Me 6)Ru(daphen)Cl][Cl] ( 8Cl[OTf]), [( p-Me- i Pr-C 6H 4)Ru(bipy)(H 2O)][OTf] 2 ( 1O[OTf] 2 ), [( p-Me- i Pr-C 6H 4)Ru(dabipy)(H 2O)][OTf] 2 ( 3O[OTf] 2 ), [( p-Me- i Pr-C 6H 4)Ru(dabipy)(H 2O)][SO 4] ( 3O[SO 4 ]), [( p-Me- i Pr-C 6H 4)Ru(daphen)(H 2O)][OTf] 2 ( 4O[OTf] 2 ), [(C 6Me 6)Ru(daphen)(MeOH)][OTf] 2 ( 8(MeOH)[OTf] 2 ), [( p-Me- i Pr-C 6H 4)Ru(dabipy)(H)][OTf] ( 3H[OTf]), [( p-Me- i Pr-C 6H 4)Ru(daphen)(H)][OTf] ( 4H[OTf]), [(C 6Me 6)Ru(dabipy-BH 2-OTf)(H)] ( 7H[-NH 2 -BH 2 -OTf]) have been determined. Under 750–1100 psi (5–7.5 MPa) of hydrogen pressure at 110 °C in the presence of acid and water in sulfolane solvent the aquo complexes form active catalysts for the selective deoxygenation of terminal diols, notably 1,2-hexanediol, to the corresponding primary alcohol, i.e., 1-hexanol in up to 60% yield. The presence of amino functions on the ortho-positions of the chelating ligands results in lower catalyst activity. Under the same reaction conditions the catalysts fail to convert glycerol to GC-detectable products. At the higher temperatures ( T > 150 °C) possibly required for glycerol activation the catalysts show increasing decomposition with increasing temperature.