Hydrothermal synthesis of dimeric lanthanide compounds X-ray structure, magnetic study and heterogeneous catalytic epoxidation of olefins

A series of dimeric lanthanide carboxylato complexes [La(5-Br-NIC)(3)(H2O)(2)](2) H2O (1) [Gd(5 Br-NIC)(3)(H2O)(2)](2) (2) [5-Br-NIC = 5-bromonicotinate] and [Sm(NIC)(3)(H2O)(2)](2) (3) [NIC = nicotinate] have been hydrothermally synthesized and structurally characterized by single crystal X-ray analysis Complexes 1 2 and 3 are of similar structure and consist of a basic unit [La(carboxylato)(3)(H2O)(2)](2) In compound 1 lanthanide cation is surrounded by one chelating 5-bromo-nicotinato ligand two bridging oxygen atoms from 5-bromo-nicotinato and two water molecules in which each La(III) ion is nine coordinated in a tricapped prismatic geometry However in compounds 2 and 3 four carboxylate groups link a pair of lanthanide atoms in the O O -bridging mode to generate a paddle wheel-like centrosymmetric dimer All the compounds exhibit excellent catalytic performance in olefin epoxidation reaction The variable temperature magnetic susceptibility measurements showed that the magnetic interaction in [Gd(5-Br-NIC)(3)(H2O)(2)](2) (2) is antiferromagnetic (J = 0 048 cm(-1)) while compound [Sm(NIC)(3)(H2O)(2)](2) (3) showed a complicated low-temperature magnetic property (C) 2010 Elsevier Ltd All rights reserved