title: Cooperative metal-ligand assisted E/Z isomerization and cyano activation at Cu(II) and Co(II) complexes of arylhydrazones of active methylene nitriles.
abstract: New (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzoic acid (H2L(4)) and known sodium 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonate (NaHL(1)), 2-(2-(dicyano-methylene)hydrazinyl)benzoic acid (H2L(2)), and sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzenesulfonate (NaHL(3)) were used in the template synthesis of a series of Cu(II) and Co(II) complexes [Cu(H2O)2L(1a)]·H2O (1), [Cu(H2O)(3-pyon)L(1b)]·H2O (2), [Cu(H2O)(4-pyon)L(1b)] (3), [Co(H2O)((CH3)2NCHO)(μ-L(2a))]2·(CH3)2NCHO (4), [Cu3(μ3-OH)(NO3)(CH3OH)(μ2-X)3(μ2-HL(3))] (5), [Cu(H2O)(py)L(3)]·H2O (6), [Cu(H2O)2(μ-L(4))]6·6H2O (7), [Cu(2-cnpy(b))2(L(1b))2]·2H2O (8), [Cu(2-cnpy(a))2(L(1a))2]·2H2O (9), and [Cu(H2O)(4-cnpy)(L(1a))2] (10), where 3-pyon = 1-(pyridin-3-yl)ethanone, 4-pyon = 1-(pyridin-4-yl)ethanone, py = pyridine, HX = syn-2-pyridinealdoxime, 4-cnpy = 4-cyanopyridine; 2-cnpy(a), 2-cnpy(b), L(1a), L(1b), L(2a) are the ligands derived from nucleophilic attack of methanol (a) or water (b) on a cyano group of 2-cyanopyridine (2-cnpy), L(1) or L(2), respectively, giving the corresponding iminoesters (2-cnpy(a), L(1a) or L(2a)) or carboxamides (2-cnpy(b) or L(1b)). An auxiliary ligand, namely syn-2-pyridinealdoxime or pyridine, acting cooperatively with the metal ion (Cu(II) in this case), induced an E/Z isomerization of the H2L(4) ligand; the E- and Z-isomers were isolated separately and fully characterized (compounds 9 and 10, respectively). A one-pot activation of nitrile groups in different molecules was achieved in the syntheses of 8 and 9. Complexes 1-10 are catalyst precursors for the solvent-free microwave (MW)-assisted selective oxidation of secondary alcohols to the corresponding ketones, with typical yields in the 29-99% range (TOFs up to 4.94 × 10(3) h(-1)) after 30 min of MW irradiation.
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , Av. Rovisco Pais, 1049-001 Lisbon, Portugal.
authors.forename: Kamran T
authors.initials: KT
authors.lastname: Mahmudov
authors.forename: Maximilian N
authors.initials: MN
authors.lastname: Kopylovich
authors.forename: Alessandra
authors.initials: A
authors.lastname: Sabbatini
authors.forename: Michael G B
authors.initials: MG
authors.lastname: Drew
authors.forename: Luísa M D R S
authors.initials: LM
authors.lastname: Martins
authors.forename: Claudio
authors.initials: C
authors.lastname: Pettinari
authors.forename: Armando J L
authors.initials: AJ
authors.lastname: Pombeiro
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006835:Hydrazones / Q000737:chemistry*; D007536:Isomerism; D008024:Ligands; D008958:Models, Molecular; D009570:Nitriles / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D006835:Hydrazones; D008024:Ligands; D009570:Nitriles; D003035:Cobalt; D003300:Copper