Kinetic stability of complexes of some d-metals with 3,3'- bis(dipyrrolylmethene) in the binary proton-donor solvent acetic acid-benzene

The kinetics of dissociation of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) binuclear homoleptic double-stranded helicates with bis(2,4,7,8,9-pentametyldipyrrolylmethen-3-yl)methane (H2L) of the [M2L2] composition in the binary proton-donor solvent acetic acid-benzene was studied. Protolytic dissociation of the helicates [M2L2] proceeds in accordance with the third order kinetic equation. Effect of the complexing metal nature is manifested in increased kinetic inertness in the following series of the helicates: [Cd2L2] < [Hg2L2] < [Cu2L2] < [Ni2L2] < [Zn2L2] < [Co2L2]. By the lability in similar environmental conditions the helicates [M2L2] are comparable to the metal complexes of distorted porphyrins and are much more inert than dipyrrolylmethenate mononuclear complexes.