Synthesis and Magnetism of -Dioximato-Bridged Heterotrinuclear Oxovanadium(IV)–Palladium(II)–Oxovanadium(IV) Complexes

Four novel oxovanadium(IV)–palladium(II)–oxovanadium(IV) heterotrinuclear complexes of the formula [(VO)2Pd(-FD)2L2]SO4, where (-FD)2 represents -furildioximato and L denotes: 5-methyl-1,10-phenanthroline (Me-phen), 2,9-dimethyl-1,10- phenanthroline (Me2-phen), 5-chloro-1,10-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 spectral studies. It is proposed that these complexes have extended dioximato-bridged structures and consist of two oxovanadium(IV) and a palladium( II) ions, in which the central palladium(II) ion has a square-planar environment and the end capped two oxovanadium(IV) ions have a square-pyramidal environment. The magnetic properties of complexes [(VO)2Pd(-FD)2(Me-phen)2]SO4 (1) and [(VO)2Pd(- FD)2(Me2-phen)2]SO4 (2) were investigated over the 4.2~300 K range and correspond to what is expected for an antiferromagnetic VO(IV)–VO(IV) pair with SVO(IV) = 1/2 and SPd(II) = 0 (Pd2+ is a diamagnetic in a square-planar environment) local spins. The exchange integral (J) was evaluated as J = 28 cm1 for (1) and J = 6.19 cm1 for (2) based on the spin Hamiltonian operator, H=- 2JS S1 x S2