Alkali-metal complexes. Part II. Compounds with two different ligands, salicylic acid, o-nitrophenol, isonitrosoacetophenone, 1-nitroso-2-naphthol, and 8-hydroxyquinoline

Abstract

Compounds of the general formula ML,HL′ have been prepared where M = Na, K, Rb, or Cs while HL and HL′ are two of the title compounds. For all pairs except isonitrosoacetophenone and 8-hydroxyquinoline the adduct obtained is that in which HL′ has a higher pK value than HL. Some pairs of ligands form adducts with all four alkali metals, others may form adducts with only some alkali metals, but the variation is not regular, e.g. sodium and rubidium salicylates form adducts with 8-hydroxyquinoline but the potassium and caesium salts do not. At a temperature higher than the melting point of HL′ the adduct decomposes to give another solid, ML. I.r. spectra of adducts are different from those of appropriate physical mixtures; most, but not all, systems in which HL and HL′ have very different pK values, absorb at 1800–1900 cm.^–1. Most solvents react with deposition of one component but in N-methylpyrrolidone both components are soluble.

K(m-nitrophenolate) with HL′= 8-hydroxyquinoline or isonitrosoacetophenone yields m-nitrophenol and KL′; in contrast the o-nitrophenolate forms adducts with these two ligands, indicating a correlation between chelation and adduct formation.