Hydrazinium Complexes of Lanthanide and Transition Metal Squarates

摘要

Reaction of the ligands,squaric acid and hydrazine with Ln(NO_3)_3 where Ln(III)=La,Pr,Nd,Sm,Gd and Ce results in the formation of the complexes of the formula,N_2H_5[Ln(C_4O_4)_2] centre dot H_2O wherex=3,5 and 6 and their reaction with transition metal nitrates,M(NO_3)_2 centre dot xH_2O,where M(II)=Co,Ni,Cu,Zn and Cd in aqueous solution yields the squarates of the types,[(N_2H_5)_3M(C_4O_4)_(2.5)] centre dot 2H_2O where M(II)=Co,Ni and Cd;[(N_2H_5)_2Zn(C_4O_4)_2] centre dot 2H_2O and [(N_2H_5)Cu(C_4O_4)_(1.5)].Neutralization of the acid with hydrazine hydrate gives dihydrazinium squarate hydrate,(N_2H_5)_2(C_4O_4) centre dot H_2O.All the above complexes,except Cd,are sparingly soluble in water and are characterized by IR,UV-visible,ESR and thermoanalytical methods.The squarates appear to behave as bis-monodentate and tetrakis-monodentate bridged ligands in transition metal and lanthanide complexes respectively.Hydrazinium cation acts as a coordinating ligand in transition metal complexes whereas it is a charge compensating species in lanthanide squarates.This fact is revealed from their IR spectra by displaying N-N frequency at 1000 cm~(-1) in the former case and at 950 cm~(-1) in the latter.Squarate compounds exhibit very high exothermic decomposition.Hydrazinium lanthanide squarates show weight losses due to dehydration and dehydrazination from 68 deg C to 258 deg C and a strong exothermic decomposition between 176 deg C and 700 deg C leading to the formation of metal oxides/oxy carbonates as the end products possibly via H[Ln(C_4O_4)_2] intermediate.Transition metal compounds loose water and hydrazine in the range of 50-275 deg C,and then undergo strong exothermic decomposition above 200 deg C with no stable intermediate formation.Simple hydrazinium salt decomposes completely exothermally at 179 deg C.The electronic spectra indicate the coordination number (CN) and geometry;CN 8 with square anti-prism for lanthanides and CN 6 with octahedral arrangement for transition metals.The geometry of the complexes is substantiated by their electronic spectra,magnetic susceptibility values and ESR study.Isomorphism among the complexes is shown by their XRD.