Synthesis, characterization and equilibrium study of the dinuclear adducts formation between nickel(II) Salen-type complexes with diorganotin(IV) dichlorides in chloroform

Adduct formation between R2SnCl2 (R = methyl and n-butyl) as acceptors, and nickel(II) complexes of tetradentate Schiff base ligands ([NiL]) where L = [3-methoxysalen, N,N′-bis(3-methoxysalicylidene)ethylenediamine], [4-methoxysalen, N,N′-bis(4-methoxysalicylidene)ethylenediamine], [5-methoxysalen, N,N′-bis(5-methoxysalicylidene)ethylenediamine], [salen, N,N′-bis(salicylaldehydo)ethylenediamine], [5-chlorosalen, N,N′-bis(5-chlorosalicylidene)ethylenediamine] and [5-bromosalen, N,N′-bis(5-bromosalicylidene)ethylenediamine] as donors have been investigated in chloroform as a solvent by means of UV–Vis spectrophotometeric analysis. Adducts have been characterized by 1H NMR, IR and electronic spectroscopy. The formation constants and the thermodynamic free energies were measured using UV–Vis spectrophotometry titration for 1:1 adduct formation at various temperatures (T = 278–308 K). The trend of the adduct formation of the nickel Schiff base complexes with a given tin acceptor decreases as follow: Ni(3-MeOSalen)>Ni(5-MeOSalen)>Ni(4-MeOSalen)Ni(3-MeOSalen)>Ni(5-MeOSalen)>Ni(4-MeOSalen) Turn MathJax on and Ni(5-MeOSalen)>Ni(Salen)>Ni(5-BrSalen)⩾Ni(5-ClSalen)Ni(5-MeOSalen)>Ni(Salen)>Ni(5-BrSalen)⩾Ni(5-ClSalen) Turn MathJax on The trend of the reaction of R2SnCl2acceptors toward a given nickel Schiff base complex is as follow: Me>n-Bu