The Reactivity of the Pentacyano(η¹‐Dioxygen)cobaltate(III) Ion in Aqueous Solution

Abstract

The mononuclear η1‐dioxygen complex [Co(CN)5O2]3− (A) decomposes in aqueous solution to the hydroxo‐complex [Co(CN)5OH]3− (B) and the hydroperoxo complex [Co(CN)5CoO2N]3 (C). The mechanism involves partial dissociation of A to give [Co(CN)5]3− (E) which binds with unreacted A to give the η1:η1‐peroxo complex [(CN)5Co02Co(CN)5]6− (F) which is hydrolysed to B and C. The mechanism is supported by the effects of pH, dioxygen concentration, and ionic strength on the rate of decomposition, and by the trapping of oxidation products of E and F. Complex A reacts readily with reducing agents to give directly the hydroperoxo complex C.

Synthesis and Characterization of Tris(tetraethylammonium) Pentacyanoperoxynitritocobaltate(III)

“…No ESR signal was detected after the reaction with nitrogen monoxide. In addition, the red color of the superoxo complex (l max 400 nm, e 1000 m À1 cm À1 ; l max 320 nm, e 2800 m À1 cm À1 [24]) changed to yellow, and a new absorption band was observed, a shoulder at 279 nm, which, in MeCN, disappeared within 1 h (Fig. 1).…”

“…They often decompose or dimerize to form mbridged peroxo or superoxo complexes. For instance, pentacyanocobaltate(II) is oxidized in H 2 O to pentacyanosuperoxocobaltate(III), which decomposes afterward [24]. However, its tetraethylammonium salt is stable in several organic solvents, such as MeCN [25].…”

Metal Hydroperoxides as Oxygen Atom Transfer Reagents

“…Transition-metal hydroperoxo complexes, LMO 2 H, (L = ligand system) are gaining increasing recognition as reactive intermediates in the reduction of O 2 by transition metal complexes in chemical − and biological systems. − As a result, several preparative routes to the more stable MO 2 H complexes have been developed, ,− and the number of known MO 2 H compounds has increased greatly in recent years. Several studies of the reactivity of such complexes have appeared, ,,,− but surprisingly little is known about the kinetics and mechanisms of such reactions.…”

A highly reactive triruthenium cluster complex bearing an alkyne coordinated in the .mu.3-.eta.2-perpendicular mode

“…The four phenyl rings of the bis(diphenylphosphino) methane ligand have been omitted for clarity. Selected interatomic distances (A) with esd's in parentheses: Ru(l)-Ru(2) = 2.652» (6), Ru(2)-Ru(3) = 2.6683 (6), Ru(l)-Ru(3) = 2.8120 (7), Ru(l)-P(l) = 2.317 (1), Ru(3)-P(2) = 2.298 (1), Ru(l)-C(9) = 2.108 (4), Ru(3)-C(9) = 2.083 (4), Ru(l)-C(10) = 2.202 (4), Ru(3)-C(10) = 2.265 (4), Ru(2)-C(10) = 2.202 (4), C(9)-C(10) = 1.409 (6).…”