Electrochemical oxidation of hydroxide ion in acetonitrile and its facilitation by transition-metal complexes

Abstract

The oxidation of hydroxide ion and phenoxide ion in acetonitrile has been characterized by cyclic voltammetry at glassy-carbon electrodes. In the presence of transition-metal complexes MnL2+ [M = Mn, Fe, Co, Ni; L = (OPPh3)4, (2,2'-bipyridine)3] and metalloporphyrins M(por) [M = Mn(III), Fe(III), Co(II); por = 5,10,15,20-tetraphenylporphinato(2-), 5,10,15,20-tetrakis-(2,6-dichlorophenyl)porphinato(2-)] the oxidation potentials for "OH and PhO" are shifted to less positive potentials. This is due to the stabilization of the oxy radical products ("OH and PhO") via formation of a d-p (d"-"OR) covalent bond. With excess "OH relative to the metal complex, oxidation of "OH is facilitated by an ECE mechanism [ML("OH) ML('OH) -22,

Ligand-centered oxidation of manganese(II) complexes

“…These values are in accord with the covalent bond strength (8 kcal) that has been observed for the hydroxide complex Mn(OPPh3)4(OH)+. 24 The shifts in potential between the first redox couple and the oxidation peak of the free ligand anion parallel the ease of oxidation for the free ligand anions. The Inorganic Chemistry, Vol.…”

CoII Complexes with Mixed Amino-N and Thiolato-S Donor Sets − Structural Characterization and Electronic Properties of a Stable Bis(μ-thiolato)-Bridged Binuclear CoII Complex

“…The one-electron oxidation of 2a at 0.6 V led to a new species 2b, exhibiting a broad absorption at 625 nm. [17] However, all attempts to crystallize the [Co II /Co III ] species failed since it reverted back to the [Co II /Co II ] complex in the solid state. The cyclic voltammogram of 2b (Figure 2, B) displays the same characteristic binuclear pattern as seen for 2 and 2a, with the exception of a zero-current potential of ϩ0.45 V. Consequently, compound 2b is proposed to be the fully oxidized binuclear Co III complex [LCo III ] 2 2ϩ .…”

Synthesis and characterization of binuclear manganese complexes: redox models for the water oxidation cofactor of photosystem II

“…Several manganese(III) complexes were prepared by conventional methods: [Mnm(acac) [(bpy)2Mnln(M-0)2Mnlv(bpy)2](C104)3 (0.551 g, 0.5 mmol) in MeCN (70 mL) was added a solution of tetramethylammonium picolinate [(Me4N)PA, 0.412 g (2.1 mmol)] in MeCN (50 mL). The solution was stirred at room temperature for 1 h and concentrated to 30 mL under reduced pressure. The resulting precipitate was removed by filtration and the filtrate concentrated to 10 mL to give a dark green precipitate.…”