Spectroscopic studies of isomerization of coordinated dihydrazone in tetranuclear dioxouranium(VI) complexes derived from bis (<i>o</i>-hydroxynaphthaldehyde) oxaloyldihydrazone

Abstract

The complexes of the types [(U0₂)₄ (napoxlhn (H₂O)₈]. 4H₂0 (I). K₄[(UO₂)₄ (napoxlh)₂ (CH₃COO)₄(H₂O)₄]. 4H₂0 (2) and K₄[(UO₂)₄(napoxlh)₂-F4(H₂O)₄] (3) have been synthesized from bis (0- hydroxynaphthaldehyde)-ox-aloyldihydrazone and characterized by elemental analysis, molecular weight determination. molar conductance and electronic. IR and' H MR spectroscopic studies. The dihydrazone coordinates to the metal centre in the anti-cis-configuration in cnol form in the complexes (1) and (3) which contain water and fluoro groups as co-ligand in the coordination sphere which function as terminal monodentate ligand. The dihydrazone isornerises to syn-cis-configuration when the bridging bidcntate acetato group is introduced into the first coordination sphere in the complex (2). The coordination of both azornethine groups of the dihydrazone to the same metal centre in anti-cis- configuration in complexes (1) and (3) leads to coupling between azomethine protons suggesting their chair contiguration while no such coupling occurs when different hydrazone parts of the dihydrazone coordinate to different metal centres in syn-cisconfiguration in complex (2) eliminating the possibility of its existence in chair conformation.