Compounds of 3,4,7,9,9,14,16-Octamethyl- (and 7,9,9,14,14,16-Hexamethyl-3,4-diphenyl) 1,2,5,6,10,13-Hexaazacyclohexadeca-2,4,6,16-tetraene With Nickel(II) and Copper(II). Preparations and Kinetics of Acid Hydrolysis Reaction

Abstract

The complex nickel(II) cation of the bis-diazine macrocycle 3,4,7,9,9,14,14,16-octamethyl-1,2,5,6,10,13-hexaazacyclohexadeca-2,4,6,16-tetraene, omht, is formed by reaction of the complex of 3,3,9,9-tetramethyl-5,8-diazadodecane-2,11-dione dihydrazone with butane-2,3-dione, and the complex of the 7,9,9,14,14,16-hexamethyl-3,4-diphenyl homologue, bzht, is similarly prepared by reaction with 1,2- diphenylethane-1,2-dione. The cation [Cu(hmtd)]²⁺ is formed by metal ion substitution for a precursor of the nickel(II) cation. Compounds of the nickel(II) cations occur as singlet ground state perchlorate salts, or as triplet ground state octahedral compounds with additional ligands, e.g. [Ni(omht)(NCS)₂], [{Ni(omht)(N₃)}₂](ClO₄)₂ and [Ni(omht)(en)] (ClO₄)₂. The singlet ground state [Ni(omht)]²⁺ cation in dimethyl sulfoxide converts into a triplet ground state species with first-order rate constant of 2.1(2)×10^-6 s^-1 at 25°C, 5.1(2)×10^-5 s^-1 at 50°C. The cations are slowly hydrolysed by acid, and pseudo-first-order rate constants in 2 mol l^-1 HCl/NaCl for hydrolysis of [Ni(omht)]²⁺ and [Cu(omht)]²⁺ at 25° and 50°C are reported. These are of the order of 10^-5 (25°C), 10^-4(50°C) s-¹, with a non-linear dependence on [H⁺], and with the reactions faster for the nickel(II) cation.