title: Mn(II) complexes containing the polypyridylic chiral ligand (-)-pinene[5,6]bipyridine. Catalysts for oxidation reactions.
abstract: A series of mononuclear and dinuclear chiral manganese(II) complexes containing the neutral bidentate chiral nitrogen ligand (-)-pinene[5,6]bipyridine, (-)-L, were prepared from different manganese salts. The chirality in these complexes arises from the pinene ring that has been fused to the 5,6 positions of one pyridine group of the bipyridine ligand. These complexes have been characterized through analytical, spectroscopic (IR, UV/Vis, ESI-MS) and electrochemical techniques (cyclic voltammetry). Single X-ray structure analysis revealed a five-coordinated Mn(II) ion in [{MnCl((-)-L)}2(mu-Cl)2] (2), [{Mn((-)-L)}2(mu-OAc)3](PF6) (3) and [MnCl2(H2O)((-)-L)] (4) and a six-coordinated one in [MnCl2((-)-L)2] (5), [Mn(CF3SO3)2((-)-L)2] (6) and [Mn(NO3)(H2O)((-)-L)2)](NO3) (7). The magnetic properties of the binuclear compounds 2 and 3 have been studied. Both compounds show a weak antiferromagnetic coupling (2, J = -0.22 cm(-1); 3, J = -0.85 cm(-1)). The catalytic activity of the whole set of complexes has been tested with regard to the epoxidation of aromatic alkenes with peracetic acid. In the particular case of styrene, good selectivities and moderate enantioselectivities were obtained. Furthermore, total retention of the initial cis configuration was achieved when epoxidizing cis-beta-methylstyrene with the chloride complexes. In general, the epoxidation activity of these manganese complexes is strongly dependent on the steric encumbrance of the substrates employed.
authors.affiliation: Departament de Química and Serveis Tècnics de Recerca Universitat de Girona, Campus de Montilivi, E-17071, Girona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Rich
authors.forename: Montserrat
authors.initials: M
authors.lastname: Rodríguez
authors.forename: Isabel
authors.initials: I
authors.lastname: Romero
authors.forename: Lydia
authors.initials: L
authors.lastname: Vaquer
authors.forename: Xavier
authors.initials: X
authors.lastname: Sala
authors.forename: Antoni
authors.initials: A
authors.lastname: Llobet
authors.forename: Montserrat
authors.initials: M
authors.lastname: Corbella
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Collomb
authors.forename: Xavier
authors.initials: X
authors.lastname: Fontrodona
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000737:chemistry; D000081008:Bicyclic Monoterpenes; D002384:Catalysis; D018360:Crystallography, X-Ray; D008024:Ligands; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000081008:Bicyclic Monoterpenes; D008024:Ligands; C545638:pinene(5,6)bipyridine; D008345:Manganese; D015082:2,2'-Dipyridyl