Polyhedron Vol. 8, No. 21, pp. 2521-2533, 1989 Printed in Great Britain 0277-5387/89 $3.co+.oLl Pergamon Press plc zyxwvutsr SYNTHESIS, CHARACTERIZATION AND STRUCTURAL ASSESSMENT OF POLYMERIC BIS(DISALICYLALDEHYDE ACYL- AND AROYL- DIHYDRAZONATO)DIOXOURANIUM(VI) COMPLEXES R. A. LAL Department of Chemistry, Pachhunga University College, North-Eastern Hill University, Aizaw1796 001, Mizoram, India zyxwvutsrqponmlkjihgfedcbaZYXWVU (Received 23 November 1988 ; accepted after revision 19 May 1989) Abstract-The reaction of uranyl nitrate hexahydrate with salicylaldehyde, and acyl- and aroyl-dihydrazines in a 1 : 4 : 2 molar ratio in ethanol medium results in complexes of the composition [UO,(H,L,),] *nH,O (n = 0, 2), where H4L2 refers to ,salicylaldehyde- oxaloyldihydrazone (H4A2), -malonoyldihydrazone (H4Bz), -succinoyldihydrazone (H&*), -glutaroyldihydrazone (H4D2), -adipoyldihydrazone (H,E,) and -phthaloyl- dihydrazone (H4F2), in high yields. The complexes have been characterized by elemental analyses, thermoanalytical data, decomposition points, molar conductance, and IR, Raman and electronic spectral data. The presence of monobasic tridentate ligands has been ascer- tained from the IR spectra. The ligands are coordinated through the phenolic oxygen, carbonyl oxygen and azomethine nitrogen atoms. All the complexes contain only one band due to the asymmetric stretching vibration of the uranyl group, indicating the same coordination environment around the uranium atom in all the complexes. The complexes are considered to be polymeric structures containing an eight-coordinated uranium atom with six ligand atoms forming an equatorial ring in a plane perpendicular to the linear uranyl group. The study of novel ligands which can bind two metals in close proximity to one another has recently created much interest among chemists, because the magneto- and electrochemical prop- erties of such complexes show promise in devel- oping theories whereby electron transport phenom- ena can be further understood. ’ Acyl- and aroyl- dihydrazones are two of the few examples of ligands which can yield binuclear, heteronuclear and poly- nuclear complexes of transition and inner-tran- sition metals possessing interesting magnetic and electrochemical properties, 2 and which can serve as models in bioinorganic chemistry. 3Acyl- and aroyl- dihydrazones derived from the condensation of o- hydroxy aromatic aldehydes and ketones, and acyl- and aroyl-dihydrazines in which two hydrazone groups are separated from each other by methylene chains of varying length or phenyl groups, con- stitute a special class of molecules. This class of molecules react in the keto, keto-enol and enol f0rms”* depending upon the mode of preparation of the complexes, the nature of the reaction medium, the pH of the reaction medium, the nature of the metal salt and the molar ratio of the metal salt, and the ligand employed, and can act as mono-, di-, tri- and tetrabasic hexadentate ligands, and give rise to polymeric complexes through both ligand- bridging due to their flexibility in three-dimensional space, and oxo-bridging through the phenolic oxy- gen atoms. Recently, we initiated studies on the isolation and characterization of uranyl complexes with acyl- and aroyl-dihydrazones in order to deter- mine the form in which the ligands coordinate to the uranyl group, the possible coordination arrangement of the donor groups around the uranyl group, the relationship between the U=O stretch- ing frequency and the increasing length of the methylene chain between the two hydrazone groups, and the effect of the presence of other ligands in the coordination sphere on the U=O stretching frequency, and also the effect of replace- ment of the methyl groups by phenyl groups on 2527