Tetrapositive Nickel as Alkali Nickel Periodates

Abstract

THE formation of the black oxides of nickel as well as of the so-called nickelites suggests that nickel can occur in a state of valency higher than its normal value of two. Both ter- and quadri-valency for nickel have been assumed in these compounds, though they have seldom been obtained in a pure state with definite composition. Some apparently double molybdates of quadrivalent nickel with alkali and alkaline earth metals have been described and studied by Hall1. We have shown that these fine purple black crystalline compounds should be regarded as salts of complex heteropoly molybdic acid with tetrapositive nickel as the central atom. Measurement of the magnetic susceptibility of these complex nickelic molybdates in our Laboratory² has shown that they are all diamagnetic. This proves that the tetrapositive nickel atom in these serves as the centre of a penetration complex with octahedral d²sp³ hybrid bonds resembling the tripositive cobalt in cobaltic complexes. A consideration of the fact that tetrapositive nickel and tripositiye cobalt possess the same number of electrons readily accounts for it.