Transition-metal carboxylate chemistry has played a key role in the conceptual development of modem inorganic chemistry. The Oxo-bridge complexes of transition metal with the general composition [M30 (O2CR)6L3]zhave been of interest for several years. Where M: Metal atom; RCOOH: carboxylic acid; L: terminal ligand such as water, methanol, pyridine (py), etc). z=I-l for M31” and z==0 for M2 “‘M ~ [1]. Two new heterotrinuclear p chlorobenzoates,[Cr2Co(O)(C7H402C1)6(Py)3]N03( 1) and [Fe2Mn(O)(C7H402C1)6(Py)3]N03(2) have been prepared as N03 salt and characterized by elemental analyses(CI-IN), spectra (infrared, electronic) studies and atomic absorption spectroscopy. These are new type of oxo-bridged mixed-metal complexes in which carboxylate li~and is p-chlorobenzoice acid. Two strong bands were observed at 1610 cm’ and 1410 cm stretching vibrations. The coordination mode of the carboxylate Iigand can be assigned on the basis of the difference (Av= 200 cm’) of these two frequencies which indicate the presence of bridging mode of coordination of ligand in the complexes [2]. Electronic spectra of the complex (1) exhibited two spin-allowed bands in the regions 17900 and 22750 (cm’) which could be assigned to the transitions from 4A2g to 4T2g and 4T1g respectively [3].

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