Reactions of pentacyanocobaltate(II) with hydrogen peroxide, hydroxylamine, and cyanogen iodide

Abstract

The oxidation of pentacyanocobaltate(H) by several molecules, namely hydrogen peroxide, hydroxylamine, and cyanogen iodide, was examined in aqueous solution. The reaction in each case conforms to the stoichiometry 2Co(CN)53-+ X-Y -Co(CN)5X3-+ Co(CN)5Y3-, where X-Y = HO-OH, HO-NH2, or I-CN. Each of the reactions exhibits second-order kinetics according to the rate lawThe values of k at 25°( M-1 sec-1), of AH± (kcal/mole), and of 5* (eu), respectively, were determined to be as follows:

Visible Light Photocatalysis of Carbon–Carbon σ-Bond Anaerobic Oxidation of Ketones with Water by Cobalt(II) Porphyrins

“…Probably, a lower temperature stabilizes the thermally labile reactive intermediate (Ph 3 P)­Co­(tap)­OH without extensive reductive elimination to give H 2 O 2 , which is detrimental to the photocatalyst. The reverse reaction, the known oxidative addition of H 2 O 2 by the analogous [Co II (CN) 5 ] 3– to give [(HO)­Co II (CN) 5 ] 3– , has been reported, thus supporting the rationale. The reductive dimerization of Rh III (ttp)­OH to generate Rh II 2 (ttp) 2 and H 2 O 2 also requires a temperature of more than 60 °C .…”

“…A few examples include the comparative studies among group 9 metalloporphyrins in aqueous solution reported by Wayland et al Furthermore, the activation of water by pentacyanocobaltate­(II) ([Co II (CN) 5 ] 3– ) to give an unfavorable equilibrium of [Co III (CN) 5 OH] 3– and [Co III (CN) 5 H] 3– is precedented but has been less explored (eq ). The macrocyclic Co II (pc) (pc = tetrakis­(neopentoxy)­phthalocyanine) also reacts with the hydroxide ion to give [Co III (pc)­(OH) 2 ] − and [Co I (pc)] − instantly (eq ). The coproduct, the cobalt­(III) hydride, can be recycled back to Co­(II) porphyrin via dehydrogenation analogous to the known reaction of cobalt­(III) dimethylglyoxime hydride (HCo­(dmgH) 2 ) by either a homolytic or heterolytic pathway to give Co­(dmgH) 2 , as reported by the groups of Espenson, Gray and Peters (Scheme ).…”

Electron transfer reactions of macrocyclic compounds of cobalt

“…The second-stage rate constant again showed a strong dependence on the concentration of the Co(I1) complex. 12 Iodine was reduced by Co(dpnH) at a slightly greater rate as shown by the data in Table 1- 21. Figure 1-35 shows k versus [12] with k = obs…”

“…The reaction stoichiometry of Co(dpnH) with Hz02 was not deter- Products of r e a c t i o n -By analogy with t h e previously reported reductions of H202 w i t h cr2+ (16), ~e ' + ( 7 , 8 ) , and CO(M) 5'- (21) t h e expected products of re-n+ a c t i o n i n t h i s study w e r e of t h e type Co(II1) (macrocycle) (H20) 2 . which was loaded onto a Sephadex column and eluted with 0.10 M HC104.…”

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

“…But it has been shown that the LF strength of a bridging cyanide coordinated via nitrogen compares well with that of ammonia [25 -27]. Co(CN) 5 NH3" exhibits its long-wavelength absorption at 346 nm (e = 230) [28]. Hence the longestwavelength band of the Co(III)(CN) 5 NC-moiety should also appear as lowest-energy absorption in the spectrum of the binuclear complex.…”