Reactions of β-diketonates with pyridinium bromide perbromide

Abstract

Reactions of PyHBr₃, with some metal (II, III, IV and VI) β-diketones/β-ketoesters/their schiff bases in ethanol medium yield various end products depending on the <em>p</em>H of the reaction. Under acidic conditions, metal (II and VI) chelates (M^II = Cu²⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺; M^VI = UO) undergo diketone ring cleavage to give solid compounds of the type [PyH]₂[MBr₄]. Some metal (III and IV) chelates (M^III= Co³⁺, Cr³⁺, Al³⁺, Fe³⁺, Mn³⁺; M^IV = Th⁴⁺) yield the usual γ-bromo products but those derived from the schiff base chelates of M(II) are unstable if left in solution. In alkaline medium, γ-bromo chelates are obtained in all the cases.