Reaction of the Pentacyanocobaltate(II) Ion with Molecular Oxygen

Abstract

By spectrophotometric scanning of reacting solutions, we have studied the processes which can occur when Oz is admitted to aqueous solutions containing the Ion [CoII(CN)5]3- in the concentration range 0.0002-0.4M, at 0�. A scheme is given to explain the formation of and inter-relations between [(CN)5CoIII-O-O-CoIII(CN)5]6-; [(CN)5CoIII-O-O-CoIV(CN)5]5-; [(CN)5CoIIIOH2]2- ; [CoIII(CN)6]3-, and a complex believed to be [(CN)5CoIII-O-OH]3-, which absorbs at 272 mp Preparative methods are described for obtaining several of the oxidation products in the crystaline state. Hydrolysis of [(CN)5CoIII-O-O-CoIII(CN)5]6- to [(CN)5CoIIIOH2]2- takes place via the 272 mμ complex, which is fairly stable in alkaline solution and is resistant to oxidation. The same 272 mμ complex can be formed more directly by oxygenation of the hydrido complex [(CN)5CoIIIH]3-, which is present in aged or hydrogenated solutions of pentacyanocobaltate(II). All of the pentacyano oxidation products can be reduced by sodium borohydride to [(CN)5CoIIIH]3-, which is further reduced by excess borohydride to an insoluble green compound and finally to metallic cobalt. We have briefly examined the reactions of ammonia and CN- with [(CN)5CoIIIOH2]2-, and the reaction of [(CN)5CoIII-O-O-CoIV(CN)5]5- with reducing agents, including [CoII(CN)5]3-.

Photochemical Redox Reaction of Aqueous Benzylpentacyanocobaltate(III)

“…If the photolysis was carried out in strongly alkaline solution (1 M KOH) a new intense absorption band occured at 311 nm when the photolyzed solution was saturated with oxygen. This band is characteristic for the superoxo complex [(NC) 5 Co0 2 Co(CN) 5 ]5-which may be formed by aerial oxidation of Co(CN)5 3~ 14 . In large scale runs the organic products of the photolysis carried out in neutral, deaerated solutions, were extracted with CH 2 C1 2 and identified by gas chromatography.…”

“…When 5 ", which may be formed by further oxidation of the peroxo complex 14 , was formed according to the spectrum of the photolyzed solution, which did not exhibit the typical absorptions of both complexes at 327 nm or 311 nm 14 . The organic product of the photolysis in neutral solutions, mainly benzaldehyde, was extracted with CH 2 C1 2 and identified by gas chromatography.…”

Photosolvation of [Co(CN)6]3−, trans-[Cr(NH3)2(NCS)4]−, and trans-[Cr(en)2NCSF]+ in aqueous mixed solvent systems

“…For K,Co(CN), the extent of reaction was determined by measuring the absorbancei of the dark aiid photolyzed soli~tions a t 380 nm ( E = 298 I 11101-~ ctn-I) (22). The extent of reaction for K-reinecitatc and t~.ut~,t-[Cr(ei~)~PdC-SF]CI04 was determined by riieasurii~g he releasetl thiocyanate as tlescribcd by Wegner and Adanison ( 18).…”

Photoredox Reactions of the Binuclear Complex Ions [(NC)5Co(III)NCM(II)(CN)5]6‐ (M = Fe and Ru)

“…However, if oxygen is present, Co(CN) 3 " may be intercepted under formation of the peroxo complex (2) [5,20]. Reaction (3) is well known to proceed in alkaline solution [5].…”

“…During the photolysis a stream of oxygen passed the solutions which were saturated with oxygen. which exhibits a very intense absorption maximum at 310 nm (s = 24800) [20]. This superoxo complex is assumed to be formed according to the following reaction scheme:…”