The Polarographic Studies of Substituent Effects in Pyridine Complexes of Transition Metals

Polarographic reduction half‐wave potentials for the series of inorganic complexes M(RC 5 H 4 N) 2 Cl 2 (M=Co(II), Ni(II), Cu(II), Zn(II), Cd(II); R=H, CH 3 , NH 2 , OH, CONH 3 , CHO, COCH 2 COPh, Cl, Br and CH 2 OH) are reported to show the substituent effects in these complexes. Consequently, the E 1/2 values correlated linearly with Hammett substituent parameters, the slope of the E σ Vs σ plots evidently decreases in order of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II).