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A Polymer‐Bound Oxidovanadium(IV) Complex Prepared from an L ‐Cysteine‐Derived Ligand for the Oxidative Amination of Styrene
Author(s) -
Maurya Mannar R.,
Kumar U.,
Correia Isabel,
Adão Pedro,
Costa Pessoa João
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200700662
Subject(s) - chemistry , amination , styrene , polymer chemistry , benzimidazole , ligand (biochemistry) , electron paramagnetic resonance , styrene oxide , polystyrene , medicinal chemistry , catalysis , organic chemistry , polymer , copolymer , biochemistry , physics , receptor , nuclear magnetic resonance
The ligand H 2 sal‐cys ( I ) derived from salicylaldehyde and L ‐cysteine has been covalently bonded to chloromethylated polystyrene cross‐linked with 5 % divinylbenzene. Upon treatment with [VO(acac) 2 ] in dimethylformamide (DMF) the polystyrene‐bound ligand PS‐H 2 sal‐cys ( II ) gave the oxidovanadium(IV) complex, PS‐[VO(sal‐cys) · DMF] ( 1 ). The corresponding neat complex, [VO(sal‐eta)] 2 ( 2 ), has also been prepared similarly in methanol. These complexes have been characterised by IR, electronic, EPR spectroscopic studies, magnetic susceptibility measurements and thermal as well as scanning electron micrographs studies. Complex [VO(sal‐eta)] 2 exhibits a medium intensity band at 980 cm –1 in the IR spectrum due to ν(V=O) stretch. Broad features of the EPR spectrum for the neat complex along with magnetic susceptibility studies suggest the presence of antiferromagnetic exchange interaction between two vanadium centers in close proximity. Both complexes catalyze the oxidative amination of styrene, in mild basic conditions, with secondary amines (diethylamine, imidazole, and benzimidazole) and gave a mixture of two aminated products in good yields. Amongst the two aminated products, the anti‐Markovnikov product is favored over the Markovnikov one due to the steric hindrance posed by the secondary amines. The polymer‐anchored heterogeneous catalyst is free from leaching during catalytic action and recyclable.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)