Synthesis,characterization and properties of nickel(II)pseudohalide complexes of types [Ni(pap)_2(X)_2],[Ni(pap)_2(X)]_2(Y)_2 and [Ni(pap)(N_3)_2]_n[pap=2-(phenylazo)pyridine;X=N_3~-,NCS ,NCO~-;Y=ClO_4~-,PF_6~-]

摘要

Three different types of nickel(II)pseudohalide compounds,viz.red-brown [Ni(pap)_2(X)_2] [pap=2-(phenylazo)pyridine;X=N_3~-,1;X=NCS~-,2;X=NCO~-,3],greenish-brown [Ni(pap)_(2-) (X)]_2(Y)_2 (X=N_3~-,Y=ClO_4~-,4;X=N_3~-,Y=PF_6,5;X=NCO~-,Y=ClO_4~-,6;X=NCO~-,Y=PF_6~-,7) and brownish-green [Ni(pap)(N_3))2]_n (8) have been prepared and characterised on the basis of microanalytical,spectroscopic,magnetic,electrochemical and other physicochemical properties.In IR,v(N=N) stretching frequency is observed at considerably lower frequencies (approx 1370 cm~(-1)) than the free ligand value (1425 cm~(-1)) indicating substantial Ni(II)->pap pi-back bonding and in electronic spectra,the MLCT bands show characteristic lower energy shifts in going from mono- to polynuclear compounds via dinuclear ones.Room temperature magnetic measurements show uniformly two-electron paramagnetism for each nickel(Il) ion in these complexes.Electrochemical electron transfer study reveals nearly-reversible responses corresponding to Ni~(III)/Ni~(II) couple in acetonitrile solutions.On the negative side of SCE,multiple ligand reductions pertaining to azo reductions are observable.