Reactivity of coordinated peroxide at a highly peroxygenated vanadium(V) center in an aqueous medium

Abstract

Reactions of a highly peroxygenated metal complex, A[V(0₂)₃.3H₂0 (A = Na, K), with S0₂(g) follow an unprecedented sequence. The deep blue ESR-silent aqueous solution of A[V(0₂)].3H₂0 readily reacts with S0₂(g) to produce a yellow, ESR-inactive solution that on further reaction with SO₂(g) affords a green-blue ESR-active (cf. V0²⁺) solution. The reaction involving K[V(0₂)₃].3H₂0 enabled isolation of the yellow intermediate characterized as K[V0(0₂)₂(H₂0)]. The product obtained from the ultimate green-blue solution has been identified as an oxo(sulfato)vanadate(IV) species, A₂[VO(S0₄)₂(H₂0)₃].H₂0(A = Na, K). At the stages of its yellow and green-blue coloration, the reaction medium pH values were recorded to be ca. 6 and ca. 2, respectively. Similarly, reactions of A[V(0₂)+3H₂0 with S0₂(g) in the presence of AF yielded ternary oxofluoro(su1fato)vanadate( 1V) compounds, A₄[VO(S0₄)₂F₂(H₂0)].2H₂O(A= Na, K). The compounds have been characterized from the results of elemental analyses, chemical determinations of oxidation states of the metals, magnetic susceptibility and ESR measurements, and IR and laser Raman spectroscopic studies. Sulfate is coordinated to the V0²⁺ center in a unidentate manner.