Studies on the complexes of 3-(o-carboxyphenyl)-1-phenyltriazene 1-oxide: Part II + Nickel(II) complex and its reaction products with some neutral N-donors

Abstract

3-(<em>o</em>-Carboxyphenyl)-1-phenyltriazene l-oxide (LH₂) reacts with aqueous solutions of nickel(II) salts to form a polymeric paramagnetic complex [NiL(H₂O)₂] of octahedral geometry which on treatment with N-donors (X) transforms to polymeric diamagnetic square-planar [NiLX] (X = NH₃, MA, EA, DMA, <em>i</em>-PA, <em>n-</em>BA<em>, i-</em>BA<em>, </em>py, <em>ɑ, β</em>, <em>γ</em>-pic, and morp) and polymeric paramagnetic octahedral [NiLX₃] (X =DMA, <em>i</em>-BA, py, <em>β</em> & <em>γ</em>-pic and morp] complexes. [NiL(H₂O)₂] and all [NiLX] complexes undergo pyrolytic change to an isolable paramagnetic intermediate [NiL], suggested to have a polymeric distorted tetrahedral geometry. The [NiL] species are, however, not isomorphous. The ligand with coordinating centres NH, NO and COOH (C = O, OH) shows different structural modes. In [NiL(H₂O)₂] and [NiL] it is tetradentate (O^-, N^-, O₂) but in [NiLX] and [NiLX₃] it is tridentate (O^-, N^-, O) due to flexible nature of carboxy group acting as bridging bidentate in the former and monodentate in the latter. The triazene is highly prone to produce mixed complexes of flexible stereochemistry in presence of nucleophiles.