Synthesis and characterization of metal complexes of methylene bridged hexadentate tetraanionic ligands

The flexibly-bridged tetraanionic hexadentate ligands (LH4), methylenbis (s alicylaldehyde-o-hydroxybenzlamine [CH2(H(2)sal-OHYBA)(2)] and methylenebis (salicylaldehyde -o-aminobenzylalcohol) [CH2(H(2)sal-OABA)(2)] react with a cetates of copper(II), nickel(II), cobalt(II), dioxouranium(VI) to give the corresponding metal complexes of formula [Cu2L], [Ni2L . 4H(2)O], [Co2L . 4H(2)O] and [(UO2)(2)L . 2CH(3)OH], respectively. Reaction of these ligands with [MO2(acac)(2)](M=Mo, W) in refluxing; methanol affords [(MO2)(2)L . n CH(3)OH] (n=0 or 2). Thermogravimetric analyses confirm the coordination of H2O/ CH3OH in complexes. H-1 NMR spectral data of molybdenum, tungsten and uranium complexes suggest coordination of the ligands through deprotonated phenolic/enolic oxygen and azomethine nitrogen atoms. Electronic spectral data suggest square planar structure for copper complexes while an octahedr al structure for other complexes.