Synthesis and magnetism of mu-dioximato-bridged heterotrinuclear oxovanadium(IV)-palladium(II)-oxovanadium(IV) complexes

Four novel oxovanadium(IV)-palladium(II)-oxovanadium(IV) heterotrinuclear c omplexes of the formula [(VO)(2)Pd(alpha -FD)(2)L-2]SO4, where (alpha -FD)( 2-) represents alpha -furildioximato and L denotes: 5-methyl-1,10-phenanthr oline (Me-phen), 2,9-dimethyl-1,10-phenanthroline (Me-2-phen), 5-chloro-1,1 0-phenanthroline (Cl-phen) and 5-bromo-1,10-phenanthroline (Br-phen), have been synthesized and characterized by elemental analyses, molar conductance and magnetic moments of room-temperature measurements, IR and electronic s pectral studies. It is proposed that these complexes have extended dioximat o-bridged structures and consist of two oxovanadium(IV) and a palladium(II) ions, in which the central palladium(II) ion has a square-planar environme nt and the end capped two oxovanadium(IV) ions have a square-pyramidal envi ronment. The magnetic properties of complexes [(VO)(2)Pd(alpha -FD)(2)(Me-p hen)(2)]SO4 (1) and [(VO)(2)Pd(alpha -FD)(2)(Me-2-phen)(2)]SO4 (2) were inv estigated over the 4.2 similar to 300 K range and correspond to what is exp ected for an antiferromagnetic VO(IV)-VO(IV) pair with S-VO(IV) = 1/2 and S -Pd(II) = 0 (Pd2+ is a diamagnetic in a square-planar environment) local sp ins. The exchange integral (J) was evaluated as J = -7.28 cm(-1) for (1) an d J = -6.19 cm(-1) for (2) based on the spin Hamiltonian operator, (H) over cap = -2J (S) over cap (1) (.) (S) over cap (2).